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Children Benefit from Mismatched Annual Flu Shots

January 14, 2022 • 6:34 am CST
(Precision Vaccinations)

A new study published in the journal Clinical Infectious Diseases on January 13, 2022, shows that influenza vaccination 'was associated' with protecting children against serious flu illness, even when infected with a flu virus that was different from the vaccine's targeted virus.

In this limited study of 159 critically ill children, the researchers estimated that vaccination effectively reduced life-threatening influenza illness by 75% during a season predominated by B/Victoria viruses and A/H1N1pdm09 subclade viruses that were antigenically drifted from vaccine components. 

Vaccination was estimated to reduce the risk of critical influenza in children by 78% against H1N1pdm09 viruses expressing matched hemagglutinin proteins and 47% against mismatched viruses.

Against antigenically drifted B-Victoria viruses, vaccination conferred an estimated 75% protection.

From these findings, the researchers inferred that vaccination prevented a substantial fraction of influenza-associated life-threatening illnesses requiring invasive mechanical ventilation, a strong predictor of death.

They also noted a record-breaking 199 pediatric deaths from influenza during the 2019-2020 flu season, when most flu viruses were caused by influenza A (H1N1) pdm09 and B-Victoria strains that were "antigenically different" from the strains in the flu vaccine.

During a flu season without circulating antigenically drifted viruses and higher coverage, the study team 'suspected that vaccine impact against life-threatening influenza illness could be more substantial.'

"This study highlights that flu can cause serious illness in children, but flu vaccines can be lifesaving. This is very good news," commented C.D.C. Director Rochelle P. Walensky, M.D., M.P.H., in a related press statement. 

These findings must be interpreted with some caveats: Critical influenza illness in children is a relatively rare occurrence reflected in the lack of randomized clinical trials evaluating protective efficacy against this outcome. Thus, the observational case-control study design.

The U.S. C.D.C. noted that the Advisory Committee on Immunization Practices recommends a flu shot every year for most individuals ages six months and older. However, influenza vaccines are manufactured differently, and different preparations have different indications as licensed by the U.S. F.D.A.

As of December 31, 2021, about 172 million flu shots had been distributed in the U.S.

Preliminary estimates for the 2020-2021 flu season indicate that about 50% of adults got a flu vaccine, with children's uptake reaching nearly 59%.

Additional flu shot news is published on this Precision Vaccinations webpage.