Influenza vaccination was over 50% effective in reducing emergency visits, hospitalizations, and critical illness among children, according to a recent study.

Researchers conducted a case-control study to evaluate the effectiveness of influenza vaccination (VE) in preventing severe influenza among children aged six months to 17 years. The study, published in JAMA Network Open, analyzed data collected between November 2015 and April 2020 from 15,728 pediatric patients presenting with acute respiratory illness at eight medical centers across the U.S.

Using a test-negative design, patients with influenza-positive results (17.2%) were compared to influenza-negative controls (82.8%) to estimate VE against varying levels of illness severity. Outcomes included emergency department (ED) visits (61.8% of influenza-positive cases), noncritical hospitalizations (33.1%), and critical hospitalizations (5.1%). Vaccination status was confirmed via parent interviews and healthcare records.

The findings revealed an overall VE of 55.7% (95% confidence interval [CI], 51.6%-59.6%) against influenza-associated ED visits or hospitalizations. VE was consistent across severity levels: 52.8% (95% CI, 46.6%-58.3%) for ED visits, 52.3% (95% CI, 44.8%-58.8%) for noncritical hospitalizations, and 50.4% (95% CI, 29.7%-65.3%) for critical hospitalizations. Among younger children (6 months to 8 years), VE was higher at 58.1% (95% CI, 53.7%-62.1%), compared to 42.6% (95% CI, 29.2%-53.5%) in older children (9 to 17 years). Vaccinated children also had shorter hospital stays and fewer intensive care unit (ICU) days than their unvaccinated counterparts.

Subgroup analyses revealed lower VE in children with underlying conditions, particularly for ED visits (36.4%; 95% CI, 20.4%-49.3%). Overlapping confidence intervals in some subgroups highlight the need for cautious interpretation. Sensitivity analyses excluding cases with prior antiviral use or those caused by influenza A(H3N2) supported these findings.

Despite the demonstrated benefits, only 49.5% of enrolled children were vaccinated. Researchers emphasized the importance of increasing vaccination coverage to reduce severe outcomes and called for further studies to evaluate VE against specific outcomes, including ICU admission and death.

Full disclosures can be found in the published study.