Influenza vaccination reduces the risk of serious illness in children even when the circulating virus is antigenically different from the vaccine virus, according to a Centers for Disease Control and Prevention (CDC) study published in the journal Clinical Infectious Diseases.

To better understand the protective benefits of influenza vaccination in children, researchers conducted active surveillance from December 2019 through April 2020 to identify pediatric patients with critical acute respiratory illness admitted to 17 US hospitals. The primary analysis included 291 patients; 159 who tested positive for influenza (case patients) and 132 who tested negative (controls).

“Using a test-negative design, we estimated vaccine effectiveness comparing odds of vaccination in test-positive case patients vs test-negative controls, stratifying by age, virus type, and severity,” the researchers explained.

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During a season predominated by 2 vaccine-mismatched viruses, vaccination was estimated to reduce the risk of life-threatening influenza illness, including invasive mechanical ventilation, CPR, and death, by 75%. Findings demonstrated that influenza vaccination reduced the risk of critical influenza illness by 78% against matched A(H1N1)pdm09 viruses, 47% against mismatched A(H1N1)pdm09 viruses, and 75% against mismatched B-Victoria viruses.

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

In a press statement, CDC Director Rochelle P. Walensky, MD, MPH welcomed the study findings and stressed the importance of flu vaccination in addition to COVID-19 vaccination 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,” she added.


  1. CDC study shows flu vaccination prevents severe flu illness in US children. News release. Centers for Disease Control and Prevention. Accessed January 14, 2022.
  2. Olson SM, Newhams MM, Halasa NB, et al. Vaccine effectiveness against life-threatening influenza illness in US children. Clinical Infectious Diseases. Published online January 13, 2022. doi:10.1093/cid/ciab931

This article originally appeared on MPR