Two recent studies from the Centers for Disease Control and Prevention’s VISION Network have found that flu vaccines were effective for all ages against both moderate and severe flu in the US during the 2022-2023 flu season.

Both the pediatric and adult VISION Network studies analyzed flu-associated emergency department/urgent care visits (indicative of moderate disease) and hospitalization (indicative of severe disease) from October 2022 through March 2023, a flu season in which far fewer individuals were social distancing or wearing masks than during the two previous flu seasons.

Vaccination reduced the risk of flu-related emergency department/urgent care visits and hospitalization for those 6 months to 17 years by almost half. For adults, regardless of age, vaccination reduced the risk of emergency department/urgent care visits by almost half and reduced the risk of hospitalization by slightly more than a third.

These results led the authors of both studies to conclude that flu vaccination is likely to substantially reduce illness, death, and strain on healthcare resources.

Both the pediatric and adult studies evaluated electronic health record data from sites across three healthcare systems in California, Utah, Minnesota, and Wisconsin.

Flu Vaccine Effectiveness: Ages 6 Months to 17 Years

Vaccination reduced the risk of flu-related emergency department/urgent care visits (moderate disease) by 48% and hospitalization (severe disease) by 40% overall across ages 6 months to 17 years. Broken down by age, risk reduction was greater for those age 6 months to 4 years than older children and adolescents.

Ages 6 months to 4 years

  • Vaccination reduced the risk of emergency department/urgent care visits (moderate disease) by 53%.
  • Vaccination reduced the risk of hospitalization (severe disease) by 56 percent.

Ages 5 to 17 years

  • Vaccination reduced the risk of emergency department/ urgent care visits (moderate disease) by 38%.
  • Vaccination reduced the risk of hospitalization by 46%.

Approximately 30% of emergency department/critical care visits for acute respiratory illness in children and adolescents were positive for flu, as were 14% of hospitalizations.

The pediatric study is published in Clinical Infectious Diseases.

Flu Vaccine Effectiveness: Ages 18-64

Vaccine effectiveness was 45% against emergency department/critical care visits(moderate disease) for adults under age 65. Effectiveness against hospitalization (severe disease) was 23%. 

Adults younger than 65 typically received standard-dose inactivated vaccines.

Flu Vaccine Effectiveness: Ages 65 and Older

Vaccine effectiveness was 41% against both flu-associated emergency department/urgent care visits (moderate disease) and hospitalization (serious disease) for this age group.

Adults age 65 and older typically received enhanced vaccine products.

The adult study is published in the Journal of Infectious Diseases.

“As with COVID, the dynamics of flu differs between children and adults. But we found that for both children and adults, vaccination significantly reduced the need for trips to the ED (emergency department) or critical care center and for hospitalization for flu-related illnesses last flu season and this is encouraging,” says Shaun Grannis, MD, MS, a co-author of both the pediatric and adult VISION Network studies, Regenstrief Institute vice president for data and analytics, and a family practice physician, in a release. “I’m hopeful that we will see similar or even better vaccine effectiveness during the current flu season. Even if they do experience symptoms, people who are vaccinated typically tend to have milder, shorter cases of the flu, a viral illness which can carry a severe disease burden.

Photo 160589101 © Leigh Prather | Dreamstime.com