Changes in Influenza Vaccination Rates After Withdrawal of Live Vaccine.

Background: Before the start of the 2016-2017 influenza season, the Advisory Committee on Immunization Practices withdrew its recommendation promoting the use of live attenuated influenza vaccines (LAIVs). There was concern that this might lessen the likelihood that those with a previous LAIV would return for an injectable influenza vaccine (IIV) and that child influenza immunization rates would decrease overall.

Methods: Using Oregon's statewide immunization registry, the ALERT Immunization Information System, child influenza immunization rates were compared across the 2012-2013 through 2016-2017 seasons. Additionally, matched cohorts of children were selected based on receipt of either an LAIV or an IIV during the 2015-2016 season. Differences between the IIV and LAIV cohorts in returning for the IIV in the 2016-2017 season were assessed.

Results: Overall, influenza immunization rates for children aged 2 to 17 years were unchanged between the 2015-2016 and 2016-2017 seasons. Children aged 3 to 10 with a previous IIV were 1.03 (95% confidence interval, 1.02 to 1.04) times more likely to return for an IIV in 2016-2017 than those with a previous LAIV, whereas children aged 11 to 17 years with a previous IIV were 1.08 (95% confidence interval, 1.05 to -1.09) times more likely to return.

Conclusions: Withdrawal of the LAIV recommendation was not associated with an overall change in child influenza immunization rates across seasons. Children with a previous (2015-2016) IIV were slightly more likely to return during the 2016-2017 season for influenza immunization than those with a previous LAIV.