Search

Introduction Tradeoffs exist between efforts to increase influenza vaccine uptake, including early season vaccination, and potential decreased vaccine effectiveness if protection wanes during influenza season. U.S. older adults increasingly receive vaccination before October. Influenza illness peaks vary from December to April. Methods A Markov model compared influenza likelihood in older adults with (1) status quo vaccination (August–May) to maximize vaccine uptake or (2) vaccination compressed to October–May (to decrease waning vaccine effectiveness impact). The Centers for Disease Control and Prevention data were used for influenza incidence and vaccination parameters. Prior analyses showed that absolute vaccine effectiveness decreased by 6%–11% per month, favoring later season vaccination. However, compressed vaccination could decrease overall vaccine uptake. Influenza incidence was based on average monthly incidence with earlier and later peaks also examined. Influenza strain distributions from two seasons were modeled in separate scenarios. Sensitivity analyses were performed to test result robustness. Data were collected and analyzed in 2018. Results Compressed vaccination would avert ≥11,400 influenza cases in older adults during a typical season if it does not decrease vaccine uptake. However, if compressed vaccination decreases vaccine uptake or there is an early season influenza peak, more influenza can result. In probabilistic sensitivity analyses, compressed vaccination was never favored if it decreased absolute vaccine uptake by >5.5% in any scenario; when influenza peaked early, status quo vaccination was favored. Conclusions Compressed vaccination could decrease waning vaccine effectiveness and decrease influenza cases in older adults. However, this positive effect is negated when early season influenza peaks occur and diminished by decreased vaccine uptake that could occur with shortening the vaccination season.

Introduction Decreased live attenuated influenza vaccine (LAIV) effectiveness in the U.S. prompted the Advisory Committee on Immunization Practices in August 2016 to recommend against this vaccine’s use. However, overall influenza uptake increases when LAIV is available and, unlike the U.S., LAIV has retained its effectiveness in other countries. These opposing countercurrents create a dilemma. Methods To examine the potential consequences of the decision to not recommend LAIV, which may result in decreased influenza vaccination coverage in the U.S. population, a Markov decision analysis model was used to examine influenza vaccination options in U.S. children aged 2–8 years. Data were compiled and analyzed in 2016. Results Using recently observed low LAIV effectiveness values, fewer influenza cases will occur if LAIV is not used compared with having LAIV as a vaccine option. However, having the option to use LAIV may be favored if LAIV effectiveness returns to prior levels or if the absence of vaccine choice substantially decreases overall vaccine uptake. Conclusions Continued surveillance of LAIV effectiveness and influenza vaccine uptake is warranted, given their importance in influenza vaccination policy decisions.

Introduction Prior studies showed that live attenuated influenza vaccine (LAIV) is more effective than inactivated influenza vaccine (IIV) in children aged 2–8 years, supporting the Centers for Disease Control and Prevention (CDC) recommendations in 2014 for preferential LAIV use in this age group. However, 2014–2015 U.S. effectiveness data indicated relatively poor effectiveness of both vaccines, leading CDC in 2015 to no longer prefer LAIV. Methods An age-structured model of influenza transmission and vaccination was developed, which incorporated both direct and indirect protection induced by vaccination. Based on this model, the cost effectiveness of influenza vaccination strategies in children aged 2–8 years in the U.S. was estimated. The base case assumed a mixed vaccination strategy where 33.3% and 66.7% of vaccinated children aged 2–8 years receive LAIV and IIV, respectively. Analyses were performed in 2014–2015. Results Using published meta-analysis vaccine effectiveness data (83% LAIV and 64% IIV), exclusive LAIV use would be a cost-effective strategy when vaccinating children aged 2–8 years, whereas IIV would not be preferred. However, when 2014–2015 U.S. effectiveness data (0% LAIV and 15% IIV) were used, IIV was likely to be preferred. Conclusions The cost effectiveness of influenza vaccination in children aged 2–8 years is highly dependent on vaccine effectiveness; the vaccine type with higher effectiveness is preferred. In general, exclusive IIV use is preferred over LAIV use, as long as vaccine effectiveness is higher for IIV than for LAIV.