Flu Shots 51.9% Effective Against Severe Influenza Hospitalization

Most health experts say 'what happens in the Southern Hemisphere is a reliable indication of the next flu season in the United States.'

This opinion is based on the yearly circulating influenza viruses and flu shot composition.

Flu seasons in the Southern Hemisphere usually occur between April and September, compared with October through May in the north.

According to a new Morbidity and Mortality Weekly Report (MMWR) published today, the 2023-2024 influenza vaccines should protect people from severe hospitalizations.

On September 8, 2023, the U.S. Centers for Disease Control and Prevention (CDC) MMWR stated the adjusted vaccine effectiveness against severe acute respiratory infection hospitalization associated with any influenza virus during the 2023 Southern Hemisphere season was 51.9% (95% Confidence Interval 39.2%–62.0%).

Despite the encouraging data, fewer than 30% of persons identified in this CDC study were vaccinated against influenza in the five countries studied before their illness onset.

This news means the circulating influenza viruses were genetically similar to those targeted by the 2023–2024 Northern Hemisphere influenza vaccine available in the U.S.

Over 100 million flu shots have already been distributed this year.

In anticipation of the new flu season, the CDC recommends U.S. healthcare providers eagerly administer seasonal influenza vaccine to all eligible persons.

The findings in this CDC report are subject to at least five limitations, and no industry conflicts of interest were disclosed. Corresponding author: Ashley L. Fowlkes, [email protected].