Prior-season influenza vaccination does not appear to reduce the effectiveness of the vaccine in children in subsequent seasons, according to a study published in JAMA Network Open.

To better understand the impact of prior-season vaccination on influenza vaccine effectiveness, researchers conducted a multiseason, test-negative case-control study among vaccinated children 2–17 years old recruited during 3 influenza seasons (2013–2014, 2014–2015, and 2015–2016). Vaccination history (vaccine type in the enrollment season as well as seasons prior to enrollment) was obtained for each participant. “To assess the association of prior-season vaccination with vaccine effectiveness during the enrollment season, a multivariable logistic regression model was used that included exposure variables for vaccination during the enrollment and prior seasons and an interaction term for vaccination during the enrollment and prior seasons,” explained the authors.

Among the children included in the analysis (N=3369), 1674 were vaccinated in the enrollment season; 772 children had tested positive for influenza. For those who received live attenuated influenza vaccine (LAIV), vaccine effectiveness against influenza A(H3N2) was found to be higher among children who received the vaccine in both enrollment and 1 prior season (50.3%; 95% CI, 17.0% to 70.2%) vs those who did not receive the vaccine in a prior season (−82.4%; 95% CI, −267.5% to 9.5%; interaction <.001). However, there was no association observed between prior-season vaccination and LAIV effectiveness against influenza A(H1N1)pdm09 or inactivated influenza vaccine (IIV) against either influenza strain. Among children not vaccinated during the enrollment season, residual protection with prior-season vaccination against influenza B was noted (LAIV: 60.0%; 95% CI, 36.8% to 74.7%; IIV: 60.0%; 36.9% to 74.6%).

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Based on the findings, the authors concluded that “prior-season vaccination history was not associated with reduced vaccine effectiveness in children, supporting current recommendations for annual influenza vaccination of children.”

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This article originally appeared on MPR