Influenza Vaccine Effectiveness and Statin Use Among Adults in the United States, 2011-2017

Abstract

Background: Statin medications have immunomodulatory effects. Several recent studies suggest that statins may reduce influenza vaccine response and reduce influenza vaccine effectiveness (VE).

Methods: We compared influenza VE in statin users and nonusers aged ≥45 years enrolled in the US Vaccine Effectiveness Network study over 6 influenza seasons (2011-2012 through 2016-2017). All enrollees presented to outpatients clinics with acute respiratory illness and were tested for influenza. Information on vaccination status, medical history, and statin use at the time of vaccination were collected by medical and pharmacy records. Using a test-negative design, we estimated VE as (1 - OR) × 100, in which OR is the odds ratio for testing positive for influenza virus among vaccinated vs unvaccinated participants.

Results: Among 11692 eligible participants, 3359 (30%) were statin users and 2806 (24%) tested positive for influenza virus infection; 78% of statin users and 60% of nonusers had received influenza vaccine. After adjusting for potential confounders, influenza VE was 36% (95% confidence interval [CI], 22%-47%) among statin users and 39% (95% CI, 32%-45%) among nonusers. We observed no significant modification of VE by statin use. VE against influenza A(H1N1)pdm09, A(H3N2), and B viruses were similar among statin users and nonusers.

Conclusions: In this large observational study, influenza VE against laboratory-confirmed influenza illness was not affected by current statin use among persons aged ≥45 years. Statin use did not modify the effect of vaccination on influenza when analyzed by type and subtype.

Keywords: influenza vaccine; statins; vaccine effectiveness.

Figure 1.

Flow diagram of study enrollment.

Figure 2.

Adjusted estimates of influenza vaccine effectiveness, stratified by statin use and virus type or subtype, with point estimates and 95% confidence interval. “Interaction” refers to interaction term for statin use and vaccination. Models adjusted for age group, sex, site, season, month of illness onset, self-rated health, diabetes, cardiovascular disease, chronic lung disease, and smoking status. Seasons included for each analysis: all influenza: 2011–2012 to 2016–2017; H1N1: 2013–2014, 2015–2016; H3N2: 2011–2012, 2012–2013, 2014–2015, 2016–2017; influenza B: 2011–2012, 2012–2013, 2014–2015, 2015–2016, 2016–2017.