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CodaVax™ RSV Vaccine May 2023

CodaVax™-RSV intranasal, live-attenuated vaccine candidate has the potential to induce innate immunity and durable local and systemic immunity. 

Codagenix Inc. is utilizing codon-deoptimized live vaccine candidates to deliver all the benefits of live vaccines on short timelines while offering unparalleled genetic stability. Codagenix's "death by a thousand cuts" approach takes the genetic sequence of the wild-type target and uses an AI-aided algorithm to compute the hundreds or thousands of sites where codons can be modified to produce the same amino acid sequence with lower translational efficiency. This process yields a small, testable number of candidate viral genomes that produce all the same proteins as the wild type but with far less virulence, exponentially accelerating timelines for candidate development. In addition, unlike previous live-attenuated RSV vaccine candidates, CodaVax-RSV is highly stable due to genetic edits that prevent wild-type reversion. 

On May 10, 2023, Codagenix announced that it initiated dosing in a pediatric Phase 1 study evaluating the CodaVax™-RSV vaccine as an age de-escalation, dose-escalation design specifically evaluating safety and immunogenicity in the 6-month to 5-year-old population. The trial is being conducted under U.S. FDA IND and Fast Track designations.

New York-based Codagenix is a clinical-stage biotechnology company leading a new era of live vaccines and viral therapeutics.

CodaVax Indication

CodaVax is indicated to prevent (RSV) infections in infants and adults. RSV is a leading cause of hospitalization due to acute lower respiratory infection, particularly in infants, young children, and elderly adults.

CodaVax News 2023

May 10, 2023 - "Codagenix is focused on providing an effective prophylactic vaccine for infants and toddlers six months to 5 years old who, based on the recent data, may be at higher risk for hospitalization following infection despite recent innovations in other RSV vaccines for the elderly that are under review," said J. Robert Coleman, Ph.D., Co-founder and Chief Executive Officer of Codagenix.

November 2, 2022 - The US FDA has granted Codagenix Fast Track Designation for CodaVax-RSV, an intranasal RSV vaccine candidate. 

June 1, 2022 - Codagenix Inc. announced that the U.S. Food and Drug Administration (FDA) has approved the Investigational New Drug (IND) application for CodaVaxTM-RSV.

CodaVax Clinical Trials

CodaVax has completed a phase 1 clinical trial and will begin recruiting for another phase 1 trial. The first phase 1 clinical trial has been completed: Safety and Immunogenicity of a Live-attenuated Vaccine Against Respiratory Syncytial Virus in Elderly Volunteers. This trial began on July 10, 2020, enrolling 36 healthy adult volunteers. The participants received two doses, 28 days apart. The vaccine was administered as nose drops.

The second phase 1 study - CodaVax-RSV in Seropositive and Seronegative Children, was Last Updated on April 20, 2023.

AREXVY™ RSV Vaccine Clinical Trials, Dosage, Efficacy, Indication, Side Effects

GlaxoSmithKline Biologicals plc (GSK) AREXVY™ recombinant, AS01E adjuvanted, single-dose RSV vaccine contains a recombinant subunit pre-fusion respiratory syncytial virus (RSV) glycoprotein antigen (RSVPreF3) combined with GSK's proprietary AS01 adjuvant. The antigen plus adjuvant combination helps overcome the natural decline in immunity that contributes to the challenge of protecting people from RSV disease. AREXVY contains Agenus' proprietary QS-21 STIMULON™ within its AS01 adjuvant, which has already demonstrated positive immune responses and a favorable safety profile. QS-21 Stimulon improves a vaccine's effectiveness by inducing strong antibody and cell-mediated immune responses. It also plays a crucial role in boosting immune response in older adults who often experience age-related decline in immunity.

On May 3, 2023, the U.S. Food and Drug Administration (FDA) approved Arexvy to prevent LRVD caused by RSV in individuals 60 and older in the U.S. (PRESCRIBING INFORMATION, Package Insert). On June 7, 2024, the FDA approved Arexvy for adults aged 50 through 59 who are at increased risk of RSV. As of October 2024, about 9 million people in the U.S. have been vaccinated with Arexvy. GSK says Arexvy is the only RSV vaccine with efficacy and safety data available through three full seasons, including in people at increased risk.

The European Medicines Agency (EMA) recommended marketing authorization in the European Union (EU) on April 26, 2023, for Arexvy for active immunization to protect adults aged 60 years and older against LRTD caused by RSV. The European Commission authorized Arexvy on June 7, 2023. The U.K.'s Medicines and Healthcare products Regulatory Agency authorized Arexvy on July 10, 2023, followed by Canada on August 4, 2023. On January 29, 2023, the EMA accepted the company's regulatory application to expand the use of Arexvy to adults aged 50-59 at increased risk for RSV disease. The EMA's Committee for Human Medicines (CHMP) issued a positive opinion for individuals aged 50-59 at increased risk of RSV disease on July 29, 2024.

On November 5, 2024, AREXVY was approved in Canada for the prevention of LRTD caused by RSV. As of January 2025, the U.S. CDC says RSV vaccines are recommended for all adults ages 75 and older and adults ages 60 – 74 who are at increased risk for severe RSV. The RSV vaccine is not currently an annual vaccine. If you have received an RSV vaccine, you should not get another RSV vaccine in 2025. On April 16, 2025, the Advisory Committee on Immunization Practices (ACIP) voted in favor of recommending the use of AREXVY in adults aged 50-59 who are at increased risk for severe RSV disease. 

GlaxoSmithKline plc (LSE/NYSE: GSK) is located in Brentford, West London, England, and is a science-led global healthcare company. For further information, please visit www.gsk.com/about-us. AREXVY trademark was issued on November 15, 2022.

AREXVY Indication

Arexvy has been approved for certain adults.

AREXVY Immunocompromised Persons

A Research Letter published by the JAMA Network on December 30, 2024, indicated AREXVY (RSVA-AS01E ) produced better results in immunocompromised persons.

AREXVY Efficacy

Phase 3 clinical trial results indicate that after a single dose of GSK’s RSV vaccine, cumulative efficacy over three full RSV seasons was clinically meaningful at 62.9% against RSV-LRTD (97.5% CI, 46.7-74.8, 48 of 12,468 vs 215 of 12,498) and 67.4% against severe RSV-LRTD (95% CI, 42.4-82.7, 15 of 12,468 vs 75 of 12,498) compared to placebo. In the third season, the vaccine’s efficacy was 48.0% against RSV-LRTD (95% CI, 8.7-72.0, 16 of 4,988 vs 61 of 10,031).

AREXVY Coadministration With Shingrix

GSK plc announced on September 18, 2024, that a Phase 3 clinical trial (NCT05966090) met the primary endpoint of non-inferior immune response when administering RSVPreF3 OA and Shingrix vaccines compared with separate vaccinations.

AREXVY Coadministration of Influenza Vaccines

Available data on the immunogenicity of coadministration of RSV vaccines and other vaccines are currently limited, says the U.S. CDC. Administering an RSV vaccine with other vaccines might increase local or systemic reactogenicity, and RSV and influenza antibody titers were somewhat lower with coadministration; however, the clinical significance of this is unknown. GSK presented acceptable coadministration with influenza vaccine data to the U.S. FDA on March 1, 2023.

AREXVY Vaccine U.S. CDC ACIP Review

The U.S. CDC Advisory Committee on Immunization Practices (ACIP) conducted a review of RSV vaccines on April 16, 2025.

And on October 24, 2024. On June 26, 2024, including these presentations, on October 25, 2023. Camille Kotton, MD, presented an overview, Monica E. Patton, MD, presented the epidemiology of RSV hospitalizations in adults, and Amadea Britton, MD, MS, presented ACIP Adult RSV Work Group Considerations. On July 21, 2023, the CDC's Morbidity and Mortality Weekly Report confirmed the efficacy of 1 dose of the GSK vaccine in preventing symptomatic, laboratory-confirmed RSV-associated LRTD was 82.6% (96.95% CI = 57.9%–94.1%) during the first RSV season and 56.1% (95% CI = 28.2%–74.4%) during the second season. Efficacy of 1 dose over two seasons was 74.5% (97.5% CI = 60.0%–84.5%) in preventing RSV-associated LRTD and 77.5% (95% CI = 57.9%–89.0%) in preventing medically attended RSV-associated LRTD. Leonard Friedland, M.D. Vice President, Scientific Affairs and Public Health, GSK, presented updated data. The ACIP committee voted to recommend Arexvy for preventing RSV disease in adults aged 60 and older with shared clinical decision-making. The committee recommendations mean that over 55 million older adults in the U.S. could have access to RSV vaccination for the first time. On February 23, 2023, presentations included Ismael R. Ortega-Sanchez, Ph.D., presented - Economics of Vaccinating U.S. Adults ≥60 years old against RSV; Evidence to Recommendations Framework. On October 20, 2022, Bishoy Rizkalla, GSK Global Medical Affairs, presented an update to the CDC's vaccine committee.

AREXVY U.S. FDA Review

The FDA conducted a Vaccines and Related Biological Products Advisory Committee (VRBPAC) AREXVY review meeting for (STN 125775/0) on March 1, 2023. The FDA published the Briefing Document, GSK SPONSOR BRIEFING DOCUMENT, and Errata to the GSK Briefing Document. The committee voted unanimously (100%) that the data supported the effectiveness of the vaccine and 10-2 that the data supported the safety of the RSV vaccine. On November 2, 2022, GSK announced that the FDA had accepted a Biologics License Application (BLA) (STN 125775/0) and granted a Priority Review for the RSVPreF3 OA vaccine candidate.

AREXVY Availability 2025

As of April 2025, Arexvy was available in major retail pharmacies in the U.S. and is recommended in Europe, Malaysia, the United Kingdom, Quebec, Canada, Australia, and various countries.

AREXVY Dosage

Prescribing information was posted on May 3, 2023. Recent in-house results from a parallel Phase III trial, AReSVi 004, showed that in participants aged 60 years and above, one dose of the RSV OA investigational vaccine induced strong humoral and cellular immune responses that remained above pre-vaccination levels up to at least the six-month post-vaccination readout time point.

AREXVY Safety Data

On January 7, 2025, the FDA required and approved safety labeling changes to the Prescribing Information, which include a new warning about the risk of Guillain-Barré syndrome. GSK announced in October 2024 that the safety and reactogenicity data were consistent with those from the Phase III program. In Season 1, the vaccine was generally well-tolerated. The most frequently observed adverse events were pain at the injection site, fatigue, myalgia, headache, and arthralgia within four days of vaccination. Data to the U.S. FDA on March 1, 2023, indicating limited safety data following vaccination in multiple studies. The EMA confirmed on April 26, 2023, the most common side effects reported were headache, tiredness, muscle pain, joint pain, and injection site pain.

AREXVY Maternal Vaccine Candidate

Arexvy is not approved for use in individuals under 60 years of age. In a clinical study that enrolled pregnant individuals who received an investigational unadjuvanted RSV vaccine containing the same RSVPreF3 antigen as AREXVY, an increase in preterm births was observed compared to pregnant individuals who received a placebo (sucrose reconstituted with saline). In the vaccine and placebo groups, 6.81% and 4.95% of preterm births were reported, respectively. The maternal RSV candidate vaccine was tested in three doses compared with a placebo in 502 healthy, non-pregnant women, with monthly visits at Days 8, 31, and 91 post-immunization. The data show that compared with the base, the investigational vaccine rapidly boosted the pre-existing immunity at all doses, leading to high levels of protective neutralizing antibodies. On Day 8, a 14-fold increase in RSV-A and RSV-B neutralizing antibody titers was observed. As of May 27, 2023, this product was on hold.

AREXVY Cost

GSK plc announced on August 17, 2023, that Arexvy costs will be covered by most U.S. Medicare and commercial insurance plans under the Inflation Reduction Act, and patients with Medicare Part D will pay no out-of-pocket expenses. As part of the Affordable Care Act, AREXVY may be covered for commercially insured patients at no cost when administered in-network.

AREXVY Vaccine News

April 16, 2025 - Tony Wood, Chief Scientific Officer, GSK commented: “We are pleased with ACIP's recommendation to expand the benefits of RSV immunization to more than 13 million adults aged 50-59 who are at increased risk for the severe consequences of this virus. RSV can have a significant impact for those with underlying medical conditions. We look forward to helping protect more people with RSV vaccination.”

October 24, 2024 - Tony Wood, Chief Scientific Officer, GSK, said in a press release, “We’re committed to working with health authorities and regulators to help adults at increased risk of RSV disease benefit from vaccination.”

October 8, 2024 - Tony Wood, Chief Scientific Officer, GSK, said: “We are excited by these new data, which show that a single dose of AREXVY could help protect millions of older adults at risk of RSV disease over three seasons, benefiting public health."

September 18, 2024 - Len Friedland, MD, Vice President of Scientific Affairs and Public Health, GSK, said in a press release, "We are excited to share data on the co‑administration of our RSV and shingles vaccines."

June 7, 2024 - Tony Wood, Chief Scientific Officer, GSK, said: “Today's approval reflects the importance of broadening the benefits of RSV immunization to adults aged 50-59 who are at increased risk. For those with underlying medical conditions, RSV can have serious consequences, so we are proud to be the first to help protect them from RSV-LRTD.”  

April 26, 2023 - The EMA recommended a marketing authorization in the European Union for Arexvy.

June 10, 2022 - GSK plc announced positive headline results from a pre-specified efficacy interim analysis of the AReSVi 006 phase III trial. The interim analysis indicates the primary endpoint was exceeded, with no unexpected safety concerns observed.

November 23, 2020 - GlaxoSmithKline plc announced that patient dosing had begun in phase 3 clinical program investigating the safety and efficacy of its RSV candidate vaccine for maternal immunization (GSK3888550A) following the presentation of positive phase 1/2 safety, reactogenicity, and immunogenicity data last month

RSV OA Vaccine Clinical Trials

The GSK RSVPreF3 RSV vaccine has been involved in various clinical studies.

GSK announced positive phase III trial results for its RSV vaccine, demonstrating an overall vaccine efficacy of 82.6% (96.95% CI, 57.9–94.1, 7 of 12,466 vs. 40 of 12,494) against RSV lower respiratory tract disease (RSV-LRTD), meeting the AReSVi 006's primary endpoint. On February 16, 2023, the NEJM published an ORIGINAL ARTICLE: Respiratory Syncytial Virus Prefusion F Protein Vaccine in Older Adults. Findings: A single dose of the RSVPreF3 OA vaccine had an acceptable safety profile in a phase 3 study and prevented RSV-related acute respiratory infection and lower respiratory tract disease and severe RSV-LRTD in adults 60 years of age or older, regardless of RSV subtype and the presence of the underlying coexisting condition. GSK funded the AReSVi-006 ClinicalTrials.gov NCT04886596.

On October 25, 2023, GSK announced preliminary results from a phase III clinical trial showing that the primary endpoints had been met, with non-inferior immune responses observed in adults aged 50-59 compared to adults aged 60 and older. Adults aged 50 and above with certain underlying medical conditions are at increased risk for RSV disease. GSK is on track to being the first company to submit data in this population to regulators, with decisions on potential label expansion expected in 2024.

The AReSVi-006 (Adult Respiratory Syncytial Virus) phase III trial is a randomized, placebo-controlled, observer-blind, multi-country demonstrating the efficacyGSK's single dose of GSK's adjuvanted RSVPreF3 OA investigational vaccine in adults aged 60 years and above. Approximately 25,000 participants from 17 countries were enrolled. AReSVi 006 is a phase III trial. Last Update Posted: June 30, 2022.

Results: 24,966 participants received one dose of the RSVPreF3 OA vaccine (12,467 participants) or placebo (12,499). Over a median follow-up of 6.7 months, vaccine efficacy against RT-PCR–confirmed RSV-related lower respiratory tract disease was 82.6% (96.95% confidence interval [CI], 57.9 to 94.1), with 7 cases (1.0 per 1000 participant-years) in the vaccine group and 40 patients (5.8 per 1000 participant-years) in the placebo group. Vaccine efficacy was 94.1% (95% CI, 62.4 to 99.9) against severe RSV-related lower respiratory tract disease (assessed based on clinical signs or by the investigator) and 71.7% (95% CI, 56.2 to 82.3) against RSV-related acute respiratory infection. Vaccine efficacy was similar against the RSV A and B subtypes (for RSV-related lower respiratory tract disease: 84.6% and 80.9%, respectively; for RSV-related acute respiratory infection: 71.9% and 70.6%, respectively). In addition, high vaccine efficacy was observed in various age groups in participants with coexisting conditions. The RSVPreF3 OA vaccine was more reactogenic than the placebo, but most adverse events for which reports were solicited were transient, with mild-to-moderate severity. The incidences of serious adverse events and potential immune-mediated diseases were similar in the two groups.

ABRYSVO™ RSV Vaccine Clinical Trials, Dosage, Efficacy, Indication, Side Effects

Pfizer Inc.'s ABRYSVO™ RSVpreF (PF-06928316) bivalent prefusion F subunit vaccine is a U.S. Food and Drug Administration (FDA) approved vaccine (STN: 125769; 125768) based on the crystal structure of prefusion F, a vital form of the viral fusion protein (F) that respiratory syncytial virus (RSV) uses to attack human cells. The vaccine comprises two preF proteins selected to optimize protection against RSV A and B. ABRYSVO builds on foundational basic science discoveries, including those made at the U.S. National Institutes of Health (NIH), which detailed the crystal structure of a critical viral protein that RSV uses to attack human cells. 

ABRYSVO is indicated to prevent RSV infections and hospitalizations in adults and infants. For infants, ABRYSVO is designed to stimulate the production of serum anti-F immunoglobulin G in the pregnant mother, which can then be transferred to the fetus across the placenta and protected for the first six months of life when the risk of hospitalization is highest. For seniors (60 years+), the ABRYSVO vaccination prevents acute respiratory disease and lower respiratory tract disease (LRTD) caused by RSV. On August 21, 2023, the FDA approved Abrysvo for use in pregnant women to prevent LRTD and severe LRTD caused by RSV in infants from birth through six months. On September 22, 2023, Abrysvo was approved by the U.S. CDC's vaccine committee for use at 32 through 36 weeks of gestational age during RSV season. On August 24, 2023, ABRYSVO became the first and only RSV vaccine approved in the European Union (EU) for older adults and pregnant women. On January 26, 2024, the CDC issued a COCA Now email alert confirming that in most of the continental U.S., the RSV vaccine should be given to pregnant people from September through January 31 each year.

On April 1, 2025, Pfizer announced today that the European Commission (EC) has extended the indication to prevent LRTD caused by RSV in individuals 18 through 59. This expands the previous EC authorization for individuals aged 60 and older in Europe.

New York-based Pfizer Inc.'s (NYSE: PFE) portfolio includes medicines, vaccines, and many of the world's best-known consumer healthcare products. ABRYSVO™ trademark Application was filed on 2021-09-09.

ABRYSVO For Pregnant Women

On June 28, 2024, the U.S. CDC vaccine committee reviewed updated Abrysvo side effects when administered to pregnant women. In clinical trials among pregnant women at 24–36 weeks of gestation, more preterm births were noted among Pfizer RSV vaccine recipients compared to placebo recipients. The label for the Pfizer RSV vaccine notes the potential risk of preterm birth under the warnings and precautions section. 

On August 21, 2023, the U.S. FDA approved Abrysvo for use in pregnant individuals to prevent LRTD and severe LRTD caused by RSV in infants from birth through 6 months of age. Abrysvo is approved for use at 32 through 36 weeks of gestational age. The FDA reported the U.S. CDC Prescribing Information for Abrysvo includes a warning to inform that a numerical imbalance in preterm births in Abrysvo recipients (5.7%) occurred compared to those who received placebo (4.7%). The FDA says the available data cannot establish or exclude a causal relationship between preterm birth and Abrysvo. Two studies evaluated the safety of Abrysvo in pregnant women. In a clinical study among approximately 3,500 pregnant individuals who received Abrysvo, compared to approximately 3,500 pregnant individuals who received a placebo, Abrysvo reduced the risk of severe LRTD by 81.8% within 90 days after birth and 69.4% within 180 days after birth. Pfizer reported in August 2023 that ABRYSVO's potential risks include preterm birth.

ABRYSVO for Immunocompromised Adults

The first assessment from an RSV vaccine study in immunocompromised adults, conducted in August 2024, showed that ABRYSVO was well-tolerated and generated strong neutralizing responses after a single dose in adults aged 18 years and above. A single 120 µg dose of ABRYSVO elicited a strong neutralizing response against all RSV subtypes, including RSV-A and RSV-B, across all cohorts and age groups in the Phase 3 study. 

ABRYSVO Side Effects

The U.S. FDA required and approved safety labeling changes on January 7, 2025, to the Prescribing Information to include a new warning about the risk for Guillain-Barré syndrome (GBS). The U.S. CDC MMWR confirmed on May 30, 2024, that GBS was identified as a potential safety concern in clinical trials. Reports of GBS (5 per million doses of the Abrysvo vaccine administered) were more common than expected background rates.

ABRYSVO Coadministration

The U.S. CDC says available data on the immunogenicity of coadministration of RSV vaccines and other vaccines are currently limited says the U.S. CDC. Administering an RSV vaccine with one or more other vaccines at the same visit might increase local or systemic reactogenicity. The U.S. CDC approved ABRYSVO for coadministration with Dtap, influenza, and COVID-19 vaccines, but not smallpox or yellow fever. Pfizer reported on May 2, 2023, positive top-line results from the Phase 3 study evaluating the safety and immunogenicity of its RSV bivalent vaccine candidate, PF-06928316 or RSVpreF, coadministered with seasonal inactivated influenza vaccine in adults 65 years and older. The study met its primary endpoint, demonstrating noninferiority for all four flu strains and RSV groups. Pfizer's Briefing Document, presented on February 28, 2023, offered limited insights into the side effects or effectiveness of ABRYSVO when coadministered with influenza vaccines in Older Adults. ABRYSVO Pregnancy

The journal Clinical Infectious Diseases published a study in October 2023 titled "Safety and Immunogenicity of Bivalent RSVpreF Vaccine Coadministered with Seasonal Inactivated Influenza Vaccine in Older Adults" that concluded: The primary study objectives were met, demonstrating the noninferiority of RSVpreF and SIIV immune responses when RSVpreF was coadministered with SIIV and that RSVpreF had an acceptable safety and tolerability profile when coadministered with SIIV. The results of this study support the coadministration of RSVpreF and SIIV in an older adult population.

ABRYSVO Vaccine U.S. CDC Review

The U.S. Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) conducted an ABRYSVO review on September 22, 2023, and February 23, 2023. The ACIP reviewed various presentations.

ABRYSVO Vaccine U.S. FDA Review

The U.S. Food and Drug Administration approved ABRYSVO™ for RSV prevention for Adults on October 23, 2024. The FDA conducted a Vaccines and Related Biological Products Advisory Committee (VRBPAC) ABRYSVO review on May 18, 2023. VRBPAC voted 14-0 regarding vaccine effectiveness in preventing severe disease in infants born to women vaccinated during pregnancy and voted 10-4 on immunization safety. In addition, the FDA's Briefing Document and Pfizer's EXECUTIVE SUMMARY were posted online. On February 28, 2023, the FDA conducted a VRBPAC meeting and published its Briefing Document, as did Pfizer. The VRBPAC voted that available data was adequate to support the safety and effectiveness of RSVpreF. The Committee voted 7 to 4 on safety and 7 to 4 on effectiveness. On February 21, 2023, the company announced the FDA had accepted for review a BLA for RSVpreF for the prevention of medically attended lower respiratory tract illness (MA-LRTI) and severe MA-LRTI caused by RSV in infants from birth up to six months of age by active immunization of pregnant individuals. The FDA has accepted the BLA for priority review and has set a PDUFA action date of August 2023. In addition, Pfizer confirmed on December 7, 2022, that the U.S. FDA accepted for priority review a Biologics License Application (STN 125769/0) for RSVpreF in individuals 60 years of age and older. In November 2018, the FDA granted Fast Track status to RSVpreF.

ABRYSVO Availability 2024

ABRYSVO's U.S. FDA approval(s) confirmed availability in late 2023. The European Medicines Agency (EMA) accepted Pfizer's ABRYSVO® marketing authorization application EMEA-002795-PIP01-20 under accelerated assessment for older adults and maternal immunization to help protect infants. On August 24, 2023, the EMA and European Commission issued approval. In February 2023, Pfizer Japan announced an application filed with the Ministry of Health, Labor, and Welfare for RSVPreF as a maternal immunization to help protect infants against RSV. In January 2023,  Health Canada approved  ABRYSVO.

ABRYSVO Safety Information

ABRYSVO should not be given to anyone with a history of a severe allergic reaction (e.g., anaphylaxis) to any of its components. Fainting can happen after injectable vaccines, including ABRYSVO. Precautions should be taken to prevent falls and injuries due to fainting. Adults with weakened immune systems, including those receiving medicines that suppress the immune system, may have a reduced immune response to ABRYSVO. In adults 60 years of age and older, the most common side effects (≥10%) were pain at the injection site, fatigue, headache, and muscle pain.

ABRYSVO Dosage

This vaccine is administered intramuscularly as a single dose of approximately 0.5 mL. A Phase III trial of a single 120 μg dose of RSVpreF, without aluminum hydroxide, is ongoing. The phase 2b study evaluated one of two dose levels of the vaccine, 120 or 240 μg, formulated with or without aluminum hydroxide.

ABRYSVO News

June 25, 2025 - Lower risk of dementia with AS01-adjuvanted vaccination against shingles and respiratory syncytial virus infections.

October 23, 2024 - Aamir Malik, Chief U.S. Commercial Officer and Executive Vice President, Pfizer, stated, “With this approval, we are proud that ABRYSVO is now the only RSV vaccine indicated for adults aged 18 to 49 at increased risk for the disease, expanding on its existing indications for older adults and pregnant women.”

Apr 8, 2024 - Pfizer Inc. announced Positive Top-Line results from a Phase 3 Study of ABRYSVO® in Adults Aged 18 to 59 at Increased Risk for RSV Disease.

January 4, 2023—Andréa Mueller, Primary Care Portfolio Lead at Pfizer Canada, commented, "For those eligible to receive the vaccine, getting vaccinated means helping to ensure babies are protected from their first breath and helping older adults continue doing what they love with a minimized risk of becoming infected. At Pfizer, we take pride in our decades of vaccine experience, helping to contribute positively to public health and the broader community."  

September 22, 2023 - Members of the Advisory Committee on Immunization Practices voted 11-1 to recommend the maternal RSV vaccine for pregnant women at 32 through 36 weeks gestation, using seasonal administration, to prevent RSV lower respiratory tract infection in infants.

February 28, 2023 - The U.S. FDA's VRBPAC voted (in favor of proceeding with ABRYSVO's BLA for older adults. Annaliesa Anderson, Ph.D., Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, Pfizer, stated in a press release, "We are encouraged by the outcome of today's VRBPAC meeting as it is a testament to the strength of our science and dedication to bringing this important vaccine candidate to the market. We look forward to working with the FDA as it completes the review of our application."

November 1, 2022 - Pfizer announced the RSVpreF investigational vaccine was well-tolerated with no safety concerns for vaccinated individuals and their newborns. The results met one of the study protocol's pre-specified regulatory success criteria.

March 24, 2022 - The U.S. FDA awarded the RSVpreF vaccine candidate Breakthrough Designation.

June 22, 2020: Pfizer announces the start of Phase 3 clinical trials. One study (NCT04424316) of the RSV vaccine candidate, RSVpreF, in pregnant women will evaluate the safety and efficacy of RSVpreF compared to a placebo in infants born to immunized pregnant women.

May 22, 2018 - Pfizer Inc. announced that it had started a Phase 1/2 trial of its respiratory syncytial virus vaccine candidate in healthy adult volunteers. The highest risk of severe outcomes from RSV occurs in the first months of life.

RSVpreF RSV Clinical Trials

The RSV preF vaccine has been and is currently conducting several clinical trials.

On April 20, 2023, the NEJM published Original Articles: Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants, and Efficacy and Safety of a Bivalent RSV Prefusion F Vaccine in Older Adults. CONCLUSIONS: RSVpreF vaccine prevented RSV-associated lower respiratory tract disease and RSV-associated acute respiratory illness in older adults (≥60 years of age) without evident safety concerns. 

ClinicalTrials.gov ID NCT05842967 - A Study to Assess the Safety, Tolerability, and Immunogenicity of RSVpreF in Adults at High Risk of Severe RSV Disease (MONET). Participants demonstrated RSV-A and RSV-B subgroup neutralizing responses non-inferior to the response seen in the Phase 3 RENOIR study of ABRYSVO in more than 34,000 adults aged 60 or older where vaccine efficacy was previously demonstrated. Participants also achieved a four-fold increase in serum neutralizing titers for RSV-A and RSV-B after receiving a receipt of ABRYSVO compared to those who had received it pre-vaccination. During the trial, ABRYSVO was well-tolerated, and safety findings were consistent with those from previous investigations of ABRYSVO in other populations.

RENOIR (NCT05035212) is a global, randomized, double-blind, placebo-controlled study designed to assess the efficacy, immunogenicity, and safety of a single dose of the vaccine in adults 60 years of age and older. The New England Journal of Medicine recently published the efficacy and safety results. RENOIR is ongoing, with efficacy data being collected in the second RSV season of the study.

MATISSE (NCT04424316) is a global, randomized, double-blinded, placebo-controlled Phase 3 study designed to evaluate the efficacy, safety, and immunogenicity of RSVpreF against medically attended lower respiratory tract illness (MA-LRT) and severe MA-LRTI due to RSV in infants born to healthy individuals vaccinated during pregnancy. The New England Journal of Medicine also recently published the efficacy and safety results.

On August 21, 2023, the FDA reported a clinical study that evaluated the effectiveness of Abrysvo in preventing LRTD and severe LRTD caused by RSV in infants born to individuals vaccinated during pregnancy. Among approximately 3,500 pregnant individuals who received Abrysvo, compared to about 3,500 pregnant individuals who received a placebo, Abrysvo reduced the risk of severe LRTD by 81.8% within 90 days after birth and 69.4% within 180 days after delivery. In a subgroup of pregnant individuals who were 32 through 36 weeks gestational age, of whom approximately 1,500 received Abrysvo and 1,500 received placebo, Abrysvo reduced the risk of LRTD by 34.7% and reduced the risk of severe LRTD by 91.1% within 90 days after birth when compared to placebo. Within 180 days after delivery, Abrysvo reduced the risk of LRTD by 57.3% and 76.5% for severe LRTD compared to placebo. The safety of Abrysvo was evaluated in two studies. In one study, approximately 3,600 pregnant individuals received a single dose of Abrysvo, and about 3,600 received a placebo. In the second study, about 100 pregnant individuals received Abrysvo, and approximately 100 received a placebo. The most commonly reported side effects by pregnant individuals who received Abrysvo were pain at the injection site, headache, muscle pain, and nausea.

In addition, although not commonly reported, a dangerous hypertensive disorder known as pre-eclampsia occurred in 1.8% of pregnant individuals who received Abrysvo compared to 1.4% of pregnant individuals who received a placebo. In the safety studies, infants' low birth weight and jaundice occurred more in the pregnant Abrysvo recipients than in pregnant placebo recipients.

The Phase 3 Study to Evaluate the Efficacy, Immunogenicity, and Safety of RSVpreF in Adults. (RENOIR), at the interim analysis (data-cutoff date, July 14, 2022), 34,284 participants had received the RSVpreF vaccine (17,215 participants) or placebo (17,069 participants). RSV-associated lower respiratory tract illness with at least two signs or symptoms occurred in 11 participants in the vaccine group (1.19 cases per 1000 person-years of observation) and 33 participants in the placebo group (3.58 points per 1000 person-years of observation) (vaccine efficacy, 66.7%; 96.66% confidence interval [CI], 28.8 to 85.8); 2 cases (0.22 cases per 1000 person-years of observation) and 14 cases (1.52 cases per 1000 person-years of observation), respectively, occurred with at least three signs or symptoms (vaccine efficacy, 85.7%; 96.66% CI, 32.0 to 98.7). RSV-associated acute respiratory illness occurred in 22 participants in the vaccine group (2.38 cases per 1000 person-years of observation) and 58 participants in the placebo group (6.30 cases per 1000 person-years of observation) (vaccine efficacy, 62.1%; 95% CI, 37.1 to 77.9). The incidence of local reactions was higher with the vaccine (12%) than with the placebo (7%); the incidences of systemic events were similar (27% and 26%, respectively). Similar rates of adverse events through 1 month after injection were reported (vaccine, 9.0%; placebo, 8.5%), with 1.4% and 1.0%, respectively, considered by the investigators to be injection-related. Severe or life-threatening adverse events were reported in 0.5% of vaccine recipients and 0.4% of placebo recipients. Serious adverse events were reported in 2.3% of participants in each group through the data-cutoff date.

Pfizer has initiated two additional clinical trials evaluating ABRYSVO. One trial is conducted in children at higher risk for RSV disease, ages 2-<18.8. A second trial is evaluating adults ages 18-60 at higher risk for RSV due to underlying medical conditions, such as asthma, diabetes, and COPD, and adults ages 18 and older who are immunocompromised and at high risk for RSV.8 Pfizer also plans postmarketing studies and surveillance programs to describe the safety of the vaccine further.

In a phase 2 efficacy study, Pfizer reported that the RSV vaccine showed 100% efficacy against mild to moderate RSV illness in adults (N=62). On June 24, 2022, the peer-reviewed journal NEJM published an original article based on the study's findings, which concluded that the RSVpreF vaccine was effective against symptomatic RSV infection and viral shedding. In addition, no evident safety concerns were identified.

In April 2020, a Phase 2b proof-of-concept study of RSVpreF achieved positive top-line results. This study evaluated the safety, tolerability, and immunogenicity of RSVpreF in vaccinated pregnant women ages 18 through 49 and their infants. Pfizer will publish outcomes from this clinical trial at a future date.

mRESVIA® (mRNA-1345) RSV Vaccine Clinical Trials, Dosage, Efficacy, Side Effects

Moderna Inc.'s mRESVIA® (mRNA-1345) Respiratory Syncytial Virus (RSV) messenger RNA (mRNA) vaccine that encodes for a prefusion F glycoprotein and uses lipid nanoparticles (LNPs), eliciting a superior neutralizing antibody response. The prefusion conformation is a significant target of potent neutralizing antibodies, and the protein sequences are primarily similar across both RSV-A and RSV-B subtypes. This mRNA is entirely made in a laboratory and instructs your body to create small pieces of proteins. In addition, this RSV vaccine contains the mRNA code for the RSV glycoprotein F. It does not cause RSV infection but helps the body's immune system recognize and protect itself if it encounters the RSV virus. Furthermore, receiving Moderna's RSV vaccine prevents you from becoming infected with RSV.

Moderna initiated a rolling submission of a Biologics License Application (STN: 125796) for mRNA-1345 to the U.S. Food and Drug Administration (FDA). On May 31, 2024, the FDA approved mRESVIA. The FDA previously granted Fast Track and Breakthrough Designation designations for mRNA-1345 in adults older than 60. On August 23, 2024, the European Commission (EC) granted marketing authorization for mRESVIA in thirty European countries. On June 12, 2025, the FDA expanded the indications for individuals 18-59 years of age who are at increased risk for RSV. This approval expands the previous indication of mRESVIA, which was approved in May 2024 for adults aged 60 years and older.

On February 14, 2025, Moderna reported $15 million in mRESVIA sales in the fourth quarter of 2024, representing $25 million for the full year 2024.

Massachusetts-based Moderna's mRNA platform builds on continuous advances in basic and applied mRNA science, delivery technology, and manufacturing and has allowed the development of therapeutics and vaccines. To learn more, visit www.modernatx.com.

mRESVIA (mRNA-1345) Vaccine Availability

Moderna expects to have mRESVIA available in the U.S. and Europe for the 2024/2025 RSV season.

mRESVIA (mRNA-1345) Vaccine Indication

The mRNA-1345 RSV vaccine candidate is indicated for the prevention of illness caused by RSV, a leading cause of respiratory disease in young children and older adults (65 years and older). RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lungs) and pneumonia (infection of the lungs) in children under one year of age. According to the U.S. CDC, RSV leads each year, on average, to approximately 58,000 hospitalizations among children younger than five years old, 177,000 hospitalizations among adults 65 years and older, and 14,000 deaths among adults 65 years and older.

mRESVIA (mRNA-1345) Vaccine Dosage

The data from a Phase 1 study in older adults ages 65-79 showed that a single mRNA-1345 vaccination of 50 µg, 100 µg, or 200 µg boosted neutralizing antibody titers against RSV-A by approximately 14-fold and against RSV-B by about 10-fold. The U.S. FDA updated the data.

mRESVIA (mRNA-1345) Vaccine Efficacy

Moderna's presentation to the U.S. Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) on June 26, 2024, disclosed that mRESVIA (mRNA-1345) showed about 81% efficacy after 3.7 months but only 50% efficacy in preventing the illness after 18 months. On October 25, 2023, the ACIP confirmed the Work Group was reviewing the safety and efficacy of Moderna's mRNA-1345 for use in adults 60 and older. On February 29, 2024, the ACIP committee reviewed the results of the Pivotal Phase 2/3 clinical trial (36,557 Participants Enrolled in 22 Countries). The mRNA-1345 vaccine was generally well tolerated in >19,500 individuals with no safety concerns. The ACIP reviewed a Phase 1 trial: Concomitant administration of influenza and COVID-19 vaccines.

mRESVIA (mRNA-1345) Vaccine Safety

The U.S. FDA published an updated Package Insert. The NEJM published an ORIGINAL ARTICLE in December 2023 - Efficacy and Safety of an mRNA-Based RSV PreF Vaccine in Older Adults. A single dose of the mRNA-1345 vaccine resulted in no evident safety concerns. It led to a lower incidence of RSV-associated lower respiratory tract disease and RSV-associated acute respiratory disease than placebo among adults 60 years of age or older. (Funded by Moderna; ConquerRSV ClinicalTrials.gov number, NCT05127434) Moderna announced in July 2023 that the vaccine candidate was well-tolerated and had a favorable safety profile. Most solicited adverse reactions were mild or moderate, and the most commonly reported solicited adverse reactions in the mRNA-1345 group were injection site pain, fatigue, headache, myalgia, and arthralgia. Moderna presented: Safety and Efficacy of mRNA-1345, an mRNA-based Vaccine Against RSV, in Adults 60 Years and Older on February 23, 2023, at the 7th ReSViNET Conference. Conclusion: mRNA-1345 was well tolerated and had an acceptable safety profile; solicited adverse reactions were mostly grade 1 or grade 2 in severity.

mRESVIA (mRNA-1345) Vaccine News

June 12, 2025 - Stéphane Bancel, Chief Executive Officer of Moderna, stated in a press release, "We appreciate the FDA's review and thank all the participants in our clinical trial as well as the Moderna team for their dedication to protecting people against RSV."

August 23, 2024 - The EC marketing authorization follows the Positive Opinion from the European Medicines Agency's Committee for Medicinal Products for Human Use. It is valid in all 27 EU member states, as well as in Iceland, Liechtenstein, and Norway.

June 28, 2024 - Moderna's chief Executive Officer said in a press release, "mRESVIA protects older adults from the severe outcomes of RSV infection, and it is the only RSV vaccine available in a pre-filled syringe designed to maximize ease of administration, saving vaccinators' time and reducing the risk of administrative errors."

May 31, 2024 - Stéphane Bancel, Chief EStéphane Bancel, Chief Executive Officer of Moderna. "mRESVIA safeguards older adults against severe RSV outcomes and is uniquely offered in a pre-filled syringe to enhance ease of administration, which can save healthcare professionals time and reduce administrative errors.

February 29, 2024 - Moderna Inc. presented an RSV vaccine update to the U.S. CDC's ACIP committee.

February 7, 2024 - Moderna Inc. posted: Respiratory Syncytial Virus (RSV): What You Need to Know.

July 5, 2023 - "We are proud to announce these filings for the use of our RSV vaccine candidate, mRNA-1345, in the European Union, Switzerland, Australia, and the U.S. RSV is a major cause of lower respiratory tract infections in older adults and significantly burden to health systems through hospitalizations and emergency care admissions," said Stéphane Bancel, Chief Executive Officer of Moderna, in a press release.

March 24, 2022 - Moderna confirmed that a Phase 1 RSV trial (mRNA-1345) is ongoing, evaluating tolerability, reactogenicity, and immunogenicity in children, younger adults, older adults, and women of childbearing age. In an interim analysis, mRNA-1345 boosted RSV-neutralizing antibodies and was well-tolerated at all doses in younger and older adults.

August 3, 2021 - Moderna, Inc. announced that the U.S. FDA had granted Fast Track designation for mRNA-1345, its investigational single-dose mRNA vaccine against RSV in adults older than 60.

April 14, 2021 - Moderna shared the first interim analysis of the Phase 1 study after 1-month post-vaccination of younger adults (18-49).

mRESVIA (mRNA-1345) Vaccine Clinical Trials

The pivotal ConquerRSV Phase 3 study of RSV in older adults (60+ years) the pivotal ConquerRSV study met both its primary efficacy endpoints, with vaccine efficacy (VE) of 83.7% (95.88% CI: 66.1%, 92.2%; p<0.0001) against RSV-LRTD as defined by two or more symptoms, and a VE of 82.4% (96.36% CI: 34.8%, 95.3%; p=0.0078) against RSV-LRTD defined by three or more symptoms. No Guillain-Barre Syndrome (GBS) cases have been reported with mRNA-1345 in the Phase 3 RSV trial. In addition to older adults, mRNA-1345 is being investigated in a fully enrolled, ongoing Phase 1 trial in pediatric populations.

Clinical Trial NCT04528719: A Dose Escalation Study to Evaluate Safety, Reactogenicity, and Immunogenicity of mRNA-1345 in Healthy Adults and Children Who Are Respiratory Syncytial Virus Seropositive. Estimated Completion Date: September 30, 2023. The study will be conducted in 2 phases: Phase 2 and Phase 3. In the Phase 2 segment, 400 and 2,000 participants will be randomly assigned to receive a single injection of either the mRNA-1345 vaccine at the selected dose or a placebo in a 1:1 randomization ratio.

On December 14, 2023, the New England Journal of Medicines published an Original Article that concluded a single dose of the mRNA-1345 vaccine led to a lower incidence of RSV-associated lower respiratory tract disease and RSV-associated acute respiratory disease than placebo among adults 60 years of age or older in a phase2/3 clinical trial. Vaccine efficacy was 83.7% (95.88% confidence interval [CI], 66.0 to 92.2) against RSV-associated lower respiratory tract disease with at least two signs or symptoms and 82.4% (96.36% CI, 34.8 to 95.3) against the disease with at least three signs or symptoms. Vaccine efficacy was 68.4% (95% CI, 50.9 to 79.7) against RSV-associated acute respiratory disease. Serious adverse events occurred in 2.8% of the participants in each trial group. On December 14, 2023, a New England Journal of Medicine op-ed discussed these results.