Flu Shot Protection Wanes 9% Monthly

It's important to remember that influenza vaccine protection starts very strong but declines throughout flu season as antibody levels wane.

A study published in Eurosurveillance on February 22, 2024, compiled data across nine flu seasons in Ontario, Canada, revealing that influenza vaccine effectiveness (VE) waned about 9% every 28 days beginning 41 days post-vaccination.

This trend was detected in adults but not in children.

According to the U.S. CDC, the overall adjusted vaccine effectiveness estimates for flu seasons in the United States from 2004-2023 was about 50%.

By recognizing that influenza vaccine protection tends to wane over time, enhanced vaccination recommendations for the timing of annual influenza vaccination wrote the investigations with the Canadian Immunization Research Network and Provincial Collaborative Network.

These researchers wrote that since most flu seasons activate in November and December and peak during January or February, vaccinating people closer to the peak time period may optimize protection,

But, delaying vaccination could inadvertently increase infections. This is why annual flu shot programs need to strike a balance between vaccinating the population too early versus too late, wrote these researchers. By taking proactive measures to address waning vaccine protection, healthcare providers can help prevent the spread of this respirator virus and better protect communities.

Since flu seasons vary by geographic location, speaking with a local health provider about your concerns is the best advice, says the CDC. This insight will help protect at-risk populations throughout the flu season, especially during peak influenza activity.

Furthermore, some people may need a second flu shot.

The CDC says certain children, older adults, and those with immunocompromized immune systems may need two doses during a single flu season.

As of late February 2024, flu shot costs are generally covered by insurance programs and remain available at most community pharmacies in the U.S.