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‘Reassuring’ evidence shows statin use does not impact flu vaccine effectiveness
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Findings from a large observational study showed that statin use had no impact on influenza vaccine effectiveness in patients aged 45 years or older, researchers reported in Clinical Infectious Diseases.
Study author Fiona J. Havers, MD, MHS, medical officer in the Division of Bacterial Diseases in the CDC’s National Center for Immunization and Respiratory Diseases, called the results “very reassuring.”
“There had been some concern raised in other studies about the association between the influenza vaccine working less well in people taking statins,” Havers told Infectious Disease News.
During three recent influenza seasons, there were an estimated 115,000 to 630,000 hospitalizations and 5,000 to 27,000 deaths associated with influenza in the United States, mostly occurring in adults aged 65 years or older comprised, Havers and colleagues reported. Older adults are also frequently prescribed statins to the reduce the risk for cardiovascular disease, they noted.
To determine the on influenza vaccine effectiveness if used during the vaccination period, Havers and colleagues analyzed data collected from patients in the U.S. Influenza Vaccine Effectiveness Network. The study population were adults aged 45 years or older with a medically attended acute respiratory infection during six influenza seasons from Jan. 1, 2011, to April 14, 2017. Medical and pharmacy records provided the researchers with information on vaccination status, medical history and statin use at the time of vaccination. Vaccine effectiveness was estimated using a test-negative design, according to the study.
The researchers included data from 11,692 patients. Of those, 30% (n = 3,359) were statin users. According to the study, 78% of statin users and 60% of nonusers received the influenza vaccine and 24% (2,806) overall tested positive for influenza. Among statin users, Havers and colleagues determined that the influenza vaccine was 36% effective (95% CI, 22-47). Among nonusers, it was 39% effective (95% CI, 32-45).
According to the study, statin use demonstrated “no significant modification” of influenza vaccine effectiveness. Furthermore, Havers and colleagues said vaccine effectiveness against influenza A(H1N1)pdm09, A(H3N2) and B viruses was similar among statin users and nonusers.
“This study has a number of strengths that some of the other studies didn’t have,” Havers said. “I won’t say this is the last word, but we did find it very reassuring. I think, especially in this population, in older adults, the influenza vaccine is the best way to prevent influenza, which caused 80,000 deaths in the United States last year. This study was reassuring that even if you’re on a statin, you can expect the vaccine will help protect you against influenza.” – by Marley Ghizzone
Disclosures: Havers reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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For this study, which was a large, very carefully done observational study, the authors found little, if any, effect of statins on influenza vaccine effectiveness. This was a large study, the population was drawn from multiple geographic sites and it encompassed six influenza seasons. As observational studies go, this is very comprehensive and rigorous. The authors tried to adjust for all potential confounding variables that they had access to. To put this into some perspective, there are other studies in the literature that do show an impact of statins diminishing the immunogenicity and the effectiveness of the influenza vaccine. We have studies, now, on both sides of the question. All the studies have been observational studies, and several of them have been sizable. What we will not have is a crisp resolution of this issue because it is not possible to do a prospective controlled, double-blind trial, which would be the classic way to examine this question. No institutional review board would permit you to do it. You cannot either give or withhold influenza vaccine or give or withhold statins in a randomized way. We are going to have studies on both sides of this question. My personal conclusion is: If there is a role of statins impacting the immunogenicity and effectiveness of the influenza vaccine, it is probably modest. I think we are where we are, and this question is unlikely to be crisply resolved in one direction or another. Mind you, there are also people who are interested in statins as a mode for treating influenza to modulate the body’s own inflammatory response. That question has not been resolved yet. I am not so sure we need more research on the question of statins and influenza vaccine immunogenicity and effectiveness. I am dubious that any study we can perform will resolve that question to everyone’s satisfaction. But the question of whether statins have a role in treatment remains intriguing.
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