Influenza vaccine effectiveness (VE) is similar among those who use statins vs those who do not, according to study findings published in Clinical Infectious Diseases.

Statins’ ability to upregulate anti-inflammatory biomarkers and inhibit pro-inflammatory pathways can attenuate the severity of influenza infection; however, previous studies examining this association have yielded inconsistent results. Investigators therefore sought to determine whether the VE of the influenza vaccine was affected by statin use. The researchers’ secondary goal was to identify and assess any associations between statin use and influenza infection.

The investigators conducted a population-based observational study in Ontario, Canada, using linked laboratory and health administrative databases to extract statin prescription claims. A test-negative design was used to evaluate heterogeneity. The study included community members at least 66 years of age who both used and did not use statins from the 2010-2011 influenza season through the 2018-2019 season (9 seasons in all).

Prior to testing, there were 54,243 participants with continuous statin exposure (mean [SD] age, 79.67 [7.79] years; 47.6% women; 21.3% positive for influenza) and 48,569 participants unexposed to statins (mean age, 80.07 [8.87] years; 58.4% women; 20.2% positive for influenza). Participants who were vaccinated against seasonal influenza were more likely to be slightly older, to have comorbidities, and to continuously use other cardiovascular drugs, and were less likely to receive home care or have prior hospitalizations. Participants who used statins were more likely to be vaccinated against seasonal influenza, to be slightly younger, to have comorbidities, and to continuously user other cardiovascular drugs.

Statin use was associated with increased odds of laboratory-confirmed influenza in vaccinated and unvaccinated subjects, but these associations might be impacted by residual confounding.

Individuals using statin had more physician office visits and hospitalizations than those who did not use statin. Investigators hypothesized that those using statin might engage in additional preventive measures and be more inclined to seek influenza testing when symptomatic than those who did not use statin, and might therefore be overrepresented in the current study among influenza-positive cases due to detection bias.

Investigators found almost identical results for VE against laboratory-confirmed influenza between statin users (17%; 95% CI, 13%-20%) vs non-users (17%; 95% CI, 13%-21%) (test for interaction, P =.87).

Those who used statins had higher odds of laboratory-confirmed influenza as those who did not, both in vaccinated participants (odds ratio [OR], 1.15; 95% CI, 1.10-1.21) and in unvaccinated participants (OR, 1.15; 95% CI, 1.10-1.20); this was consistent by statin type and mean daily dose, but not consistent across seasons.

In sub-analysis, individuals using beta-blockers did experience a difference in VE with increased odds of influenza infection among those who were also unvaccinated (OR, 1.10; 95% CI, 1.05-1.16). Individuals using other cardiovascular drugs did not experience a VE difference nor any increase in the odds of influenza infection (regardless of vaccination status) compared to those not using these drugs. Additionally, a lower odds of laboratory-confirmed influenza was found among those continuously using calcium-channel blockers who were vaccinated had (OR, 0.91; 95% CI, 0.87-0.96), and those using diuretics who were both unvaccinated (OR, 0.94; 95% CI, 0.90-0.99) and vaccinated (OR, 0.95; 95% CI, 0.90-0.99). No association was found between increased odds of influenza infection and continuous use of fibrates and other anti-lipidemic drugs.

Study limitations include possible selection bias, and the use of filled prescriptions as a surrogate for continuous use.

“Influenza VE did not differ between statin users and non-users,” investigators concluded. They wrote “Statin use was associated with increased odds of laboratory-confirmed influenza in vaccinated and unvaccinated subjects, but these associations might be impacted by residual confounding.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

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