Statins Don't Appear to Affect Influenza Vaccine Effectiveness in Elderly
Pharmacists can now reassure older people that use of statins is unlikely to affect the effectiveness of their annual influenza vaccine. Here's how a new study reached that conclusion, despite previous research suggesting the cholesterol-lowering medications could increase risk of flu.
SILVER SPRING, MD – A series of studies over the last few years have alarmed infectious disease experts by suggesting that use of statins reduced influenza vaccine effectiveness and increased the likelihood of infection.
To better understand the possible risks, recently published in Clinical Infectious Diseases employed Medicare data to evaluate associations between statins and risks of influenza among those who were vaccinated.
A study team led by researchers from the Center for Biologics Evaluation and Research at the Food and Drug Administration identified Medicare beneficiaries 65 and older years who received high-dose (HD) or standard-dose (SD) influenza vaccines at pharmacies from 2010-11 through 2014-15.
In the retrospective cohort study, statin users were matched to non-users by vaccine type, demographics, prior medical encounters, and comorbidities. Researchers then estimated associations between statin use around the time of vaccination and risk of influenza-related encounters. Among the designated outcomes were influenza-related office visits with a rapid test followed by dispensing of oseltamivir, and influenza-related hospitalizations – including emergency department visits -- during high influenza circulation periods.
Ultimately, the study included 1.4 million statin users matched to non-users, with well-balanced cohorts.
Results indicate that the adjusted relative risk was 1.086 (95% confidence interval [CI] 1.025-1.150) for influenza-related visits and 1.096 (95% CI 1.013-1.185) for influenza-related hospitalizations for statin users vs. non-statin users. Risk differences varied from -0.02 to 0.23 for influenza-related visits and from -0.04 to 0.13 for hospitalizations, depending on seasonal severity.
Little difference was detected with HD compared to SD vaccines, or for non-synthetic and synthetic statin users.
"Among 2.8 million Medicare beneficiaries, these results suggest that statin use around time of vaccination does not substantially affect the risk of influenza-related medical encounters among older adults," study authors conclude.
The national Centers for Disease Control and Prevention notes on its website that two recent studies had raised the "possibility that statin medications may blunt the effectiveness of influenza vaccines in seniors."
Calling for more research, the CDC adds, "Because of their benefits, seniors should not stop taking their statin without consultation with their healthcare provider. Influenza vaccine remains the best protection we have against influenza and provides at least some protection in people who take statins, so patients should still receive an influenza vaccine to be protected." Those studies never affected recommendations for influenza vaccine, public health officials point out.