Disclosures: Walensky reports no relevant financial disclosures. Please see the study for all authors' relevant financial disclosures.
January 13, 2022
1 min read

Even poorly matched flu vaccines protect children from serious illness, study shows

Disclosures: Walensky reports no relevant financial disclosures. Please see the study for all authors' relevant financial disclosures.
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A new study reinforced that influenza vaccination protects children from serious illness even when vaccines are a poor match for circulating viruses.

The study’s authors found that vaccination during the 2019-2020 season was 63% effective overall against critical influenza among children. Vaccination reduced the risk for severe influenza among children by 78% against influenza A viruses that matched the vaccine viruses, by 47% against mismatched influenza A viruses, and by 75% against mismatched influenza B-Victoria viruses, they reported.

The study comprised 291 patients in 17 U.S. hospitals — 159 children who were critically ill with influenza and 132 controls.

The researchers said the provided a “unique” opportunity to study the effect of influenza vaccines against antigenically drifted viruses because the vaccines contained two poorly matched virus strains. Influenza B viruses dominated early, “causing the largest national influenza epidemic in children since 1992,” they wrote.
CDC Director Rochelle P. Walensky, MD, MPH, said the study was “good news.”

Rochelle Walensky

“This study highlights that flu can cause serious illness in children, but flu vaccines can be lifesaving,” Walensky said in a press release highlighting the study in Clinical Infectious Diseases. “It’s especially important that children get a flu vaccine in addition to their recommended COVID-19 vaccines this season. Flu season has started and currently flu vaccination is down in children, so now is the best time to get your child vaccinated, if you have not already.”

Influenza season has started in many parts of the U.S., with continued influenza activity expected over the coming weeks, the CDC said. Most influenza detected so far has been caused by the influenza A(H3N2) and occurred among children and young adults. The circulating viruses are genetically closely related to the H3N2 vaccine virus but have some differences that may result in reduced protection against those viruses from the vaccine, according to the CDC.

CDC. Vaccine protects, even when vaccine virus and circulating viruses are different. https://www.cdc.gov/media/releases/2022/p0113-flu-vaccine-children.html. Accessed January 13, 2022.