Getting Flu Vaccine One Year Doesn't Reduce Vaccine Effectiveness the Next Year

By Amy Orciari Herman

Edited by Susan Sadoughi, MD, and André Sofair, MD, MPH

Getting the flu vaccine every year doesn't reduce its effectiveness — and might even boost its performance — suggests a study in JAMA Network Open.

Researchers examined the vaccination status of nearly 3400 children who presented with acute febrile respiratory illness during one of three successive flu seasons between 2013 and 2016. About one-fourth had flu confirmed on reverse-transcription polymerase chain reaction testing; the rest were considered negative for flu.

The researchers found that while vaccine effectiveness varied by vaccine type (e.g., live attenuated influenza vaccine [LAIV) or inactivated influenza vaccine) and flu virus strain, past-season vaccination did not reduce vaccine effectiveness. In fact, in some cases — for example, the effectiveness of LAIV against influenza A(H3N2) — previous vaccination appeared to improve the vaccine's effectiveness.

Of note, residual protection from past-season flu vaccine alone was observed only for influenza B.

A commentator writes, "The results thus suggest additional support for the current Advisory Committee on Immunization Practices' recommendation that children be vaccinated annually against influenza."