Flu Shot Shields Kids Across Severity Levels

TOPLINE:

Influenza vaccination demonstrates consistent effectiveness of approximately 50% across all severity levels in children, with higher protection observed in younger children (age, 6 months to 8 years) than the older ones (age, 9-17 years).

METHODOLOGY:

• Researchers conducted a test-negative case-control study to evaluate the vaccine effectiveness (VE) against severe influenza in children across eight pediatric medical centers in the United States from November 2015 through April 2020.
• In total, 15,728 children (44.6% girls) who were hospitalized or presented to an emergency department (ED) with acute respiratory illness at participating hospitals were enrolled. Among them, 85.5% were between 6 months and 8 years of age, and the remaining 14.5% were between 9 and 17 years of age.
• Overall, 13,018 children were influenza test negative, while remaining 2710 were influenza test positive and their severity of influenza was categorized into those requiring an ED visit (61.8%), those requiring hospitalization for noncritical influenza (33.1%), and those requiring hospitalization for critical influenza (5.1%).
• Children aged ≥ 9 years were classified as vaccinated if they received at least one dose of the current season’s influenza vaccine 14 or more days before symptom onset.
• VE was calculated as per the influenza severity and vaccination status.

TAKEAWAY:

• Overall, 49.5% of children were vaccinated, most (87.3%) being between 6 months and 8 years of age. Unvaccinated children had a longer length of hospital stay and more ICU days than vaccinated children, if hospitalized.
• The overall VE after receiving at least one dose of influenza vaccine was 55.7% (95% CI, 51.6-59.6%) and was higher in children aged between 6 months and 8 years than in those aged between 9 and 17 years (58.1% vs 42.6).
• The VE remained consistent across severity levels: 52.8% for illness requiring ED visits, 52.3% for noncritical illness requiring hospitalization, and 50.4% for critical illness requiring hospitalization.

IN PRACTICE:

“Vaccination is one of the most effective ways to protect children against influenza and its complications, including severe illness and hospitalization. Improving vaccine uptake in children may reduce influenza illness and, subsequently, ED and hospital visits in a time of increased respiratory virus co-circulation,” the authors wrote.

SOURCE:

The study was led by Kelsey M. Sumner, PhD, MSPH, National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta. It was published online on December 27, 2024, in JAMA Network Open.

LIMITATIONS:

Requirement of written informed consent led to noninclusion of many children, particularly those in critical condition. The population with severe disease may reflect a milder form, with only two deaths reported over 5-year study period. Other limitations included the limited inclusion of patients not visiting the ED, as well as the lack of generalizability of the findings to a broader population.

DISCLOSURES:

The study was supported by the Centers for Disease Control and Prevention (CDC). Several authors have reported receiving grants from the CDC during the study and personal fees, grants, and honoraria from various pharmaceutical organizations.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.