No significant benefit seen for two doses when the age range was broadened to children younger than 9 years
By Lori Solomon HealthDay Reporter
FRIDAY, Oct. 17, 2025 (HealthDay News) — Receiving two doses of inactivated influenza vaccine (IIV) in the first year of influenza vaccination is associated with improved protection for children younger than 3 years versus one dose, according to a study published online Oct. 3 in JAMA Network Open.
Jessie J. Goldsmith, from University of Melbourne in Australia, and colleagues conducted a systematic literature review to estimate the increase in protection associated with the second dose of influenza vaccine for influenza vaccine-naive children younger than 9 years.
Based on 51 studies (415,050 participants), the researchers found that the pooled absolute increase in vaccine effectiveness of a second inactivated influenza vaccine dose in the first year of vaccination was 15 percentage points (pp) for those younger than 9 years (95 percent confidence interval [CI], −2.8 pp to 33 pp) and 28 pp (95 percent CI, 4.7 pp to 51 pp) for children younger than 3 years. It was not possible to assess the incremental benefit associated with a second dose of live attenuated influenza vaccine.
“Our findings suggest the second dose of inactivated influenza vaccine confers additional protection for influenza vaccine-naive children <3 years but that the benefit attenuates with age,” the authors write.
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