Prior-season influenza vaccination history was not associated with reduced vaccine effectiveness in children, according to study results published in JAMA Infectious Diseases.
Due to the expanded recommendations for annual influenza vaccination, the effectiveness of prior vaccination on influenza vaccine has become an area of great interest. An increasing number of studies have assessed the association of prior influenza vaccination with vaccine effectiveness. However, data has been variable across seasons and studies during the same season, making interpretation of findings challenging.
In addition, although these studies have included children, there is a lack of studies that specifically assess prior vaccination in children or that have examined the effect of vaccinations received in the prior 2 or 3 seasons.
Further, there is a lack of knowledge regarding prior vaccination effects in children who receive the live attenuated influenza vaccine vs the inactivated influenza vaccine that may contribute to the varying effects of prior vaccination due to the different mechanisms of protection each vaccine provides. Therefore, this multi-season, test-negative case control study aimed to assess the association of prior-season influenza vaccination with subsequent vaccine effectiveness in children age 2 to 7 years over 3 influenza seasons.
A total of 3369 children (52% male; median age, 6.6 years) with a medically attended febrile acute respiratory illness were included from 4 outpatient clinics in the United States during the 2013 to 2014, 2014 to 2015, and 2015 to 2016 influenza seasons. Data regarding vaccination history, including influenza vaccine type received in the enrollment season and the season before enrollment (live attenuated influenza vaccine, inactivated influenza vaccine, or no vaccine) were collected from medical records and immunization registries. Cases were defined as children with influenza confirmed by reverse-transcription polymerase chain reaction; test-negative control participants were defined as children with negative influenza results. Positive test results for influenza were confirmed in 23% of participants and 50% were vaccinated in the enrollment season.
In participants who received live attenuated influenza vaccine, vaccine effectiveness against influenza A(H3N2) was higher in children who were vaccinated in both the enrollment and prior season (50.3%) when compared with children without prior season vaccination (−82.4%; P <.001). Since the live attenuated influenza vaccine has been shown to boost durable and cross-reactive T cell responses in children, this may have contributed to the greater protection seen against influenza A(H3N2). However, this trend was not seen in live attenuated influenza vaccine recipients against influenza A(H1N1)pdm09, as vaccine effectiveness was not seen in either children who received prior season vaccination (47.5%) or children who did not receive prior season vaccination (7.8%; P =.37). In addition, prior season vaccination was not associated with effectiveness of inactivated influenza vaccine against influenza A(H3N2) (P =.16) or against influenza A(H1N1)pdm09 (P =.93). In children who did not receive a vaccination in the enrollment seasons, residual protection from prior season vaccination was only observed for influenza B (live attenuated influenza vaccine: 60.0%; inactivated influenza vaccine: 60.0%). Further, analyses that included repeated vaccination in 2 and 3 prior seasons showed similar results.
Overall, the study 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.”
McLean HQ, Caspard H, Griffin MR, et al. Association of prior vaccination with influenza vaccine effectiveness in children receiving live attenuated or inactivated vaccine. JAMA Network Open. 2018;1(16):e183742.