Statin Use Reduces Effectiveness of Flu Vaccine in Certain Populations

Statins are known to have immunomodulatory effects and anti-inflammatory properties that can affect the clinical course of a variety of infectious processes including sepsis, bacteremia, community-acquired pneumonia, and laboratory-confirmed influenza. Researchers have wanted to find out if statins may also affect the initial immune response to vaccines because if statins affected vaccine responsiveness (VE) in individuals, their widespread use could influence overall VE in a population.

Two studies published in The Journal of Infectious Diseases show that statins reduce the VE of influenza vaccine in elderly people and in medically attended acute respiratory illnesses (MAARI).

Researchers from Novartis Vaccines in Germany and Italy and from the Center for Global Health at Cincinnati Children’s Hospital used data from a large (>5000 participants) comparative immunogenicity study of adjuvanted and unadjuvanted flu vaccines in elderly individuals in a post hoc analysis.

Comparison of hemagglutination-inhibiting geometric mean titers revealed that titers were 38% lower for influenza A(H1N1) strain, 67% lower for the A(H3N2) strain, and 38% lower for the B strain in patients receiving chronic statin therapy, compared with patients not receiving chronic statin therapy.

“This apparent immunosuppressive effect of statins on the vaccine immune response was most dramatic in individuals receiving synthetic statins,” the authors noted.

The effects were seen in both adjuvanted and unadjuvanted vaccine groups. The investigators concluded that if these results are confirmed, they could have implications for both future clinical trial design and vaccine use recommendations for elderly people.

In the study assessing VE in MAARI patients taking statins, investigators at Emory University conducted a retrospective cohort study over 9 influenza seasons using research databases of large managed care organizations in the southeastern United States.

Flu vaccination and statin prescription statuses of cohort members and MAARI patients were ascertained on a per-season basis. Even after adjustment for covariates of vaccine responsiveness, statin receipt, and health-seeking behavior, the observed reduction in influenza VE among statin users was significant for periods of widespread flu circulation among statin versus nonusers (12.6% vs 26.2%; mean difference, 18.4%; 95% CI, 2.9%-36.2%). There was a nonsignificant trend toward reduced VE during periods of local circulation as well (14.1% vs 22.9%; mean difference, 18.4%; 95% CI, -7.1%-26.1%).

Many cases of MAARI are not caused by influenza, which means there is a need for studies of the impact of statins on influenza VE against lab-confirmed influenza, investigators noted.

“More data are needed in this area to provide meaningful guidance for vaccine and statin use in the population,” the authors concluded. “If confirmed, our findings have potential implications for clinical guidelines regarding statin use around the time of routine vaccinations.”