Flu shot not as effective for seniors on statins

By John Murphy, MDLinx
Published October 29, 2015

Key Takeaways

Two new studies suggest that statins may weaken the effectiveness of the influenza vaccine in older adults.

In one study, elderly patients on long-term statin therapy had a significantly reduced immune response to the flu vaccine, compared with those not taking statins.

In the other study, the vaccine’s effectiveness at preventing serious respiratory illness was lower among patients on statins compared with patients not on statins.

If confirmed by additional research, these studies will have implications for flu vaccine recommendations, guidelines for statin use around the time of vaccination, and future clinical trials of vaccines in seniors, the authors noted. Both studies were published October 29, 2015 in The Journal of Infectious Diseases.

Statin effect on immune response

In one study, researchers analyzed immune response data from nearly 7,000 senior adults (≥65 years) taken from an earlier flu vaccine clinical trial conducted during the 2009-2010 and 2010-2011 flu seasons.

After analyzing the data, the investigators found that long-term statin users had a significantly reduced immune response to vaccination compared with those not taking statins, as measured by the level of antibodies to the flu vaccine strains in patients’ blood 3 weeks after vaccination. (Antibodies to the H1N1 virus strain were 38% lower in subjects on chronic statin therapy, antibodies to the H3N2 strain were 67% lower, and antibodies to the B strain were 38% lower, compared with those not on statins.)

Investigators also found that patients on fermentation-derived statins had higher levels of antibodies than those on synthetic statins, which indicated that synthetic statins had a greater immunosuppressive effect on the vaccine response.

“Apparently, statins interfere with the response to influenza vaccine and lower the immune response, and this would seem to also result in a lower effectiveness of influenza vaccines,” said the study’s lead author Steven Black, MD, a pediatric infectious disease specialist at Cincinnati Children’s Hospital Medical Center in Cincinnati, OH.

“This observed negative effect should be taken into account when evaluating the immunogenicity of influenza vaccines in elderly individuals in the future,” the authors concluded.

If confirmed, this finding could support the preferential use of a high-dose flu vaccine or vaccines containing adjuvants in order to boost the immune response in elderly patients and counteract the apparent effect, the authors wrote.

Statin effect in respiratory illness

In the other study, researchers at Emory University in Atlanta, GA, investigated whether statins impact the flu vaccine’s effectiveness in preventing serious respiratory illness. The researchers analyzed data from 9 flu seasons (2002-2011), including information about flu vaccination, statin prescriptions, and cases of medically attended acute respiratory illness (MAARI) among nearly 140,000 people enrolled in a large managed care organization in Georgia.

“What we found was a potential signal that the effectiveness of flu vaccine in older people may be compromised somewhat if they are on statins, compared to those who are not on statins,” said the study’s lead author Saad B. Omer, MBBS, MPH, PhD, an Associate Professor of Global Health, Epidemiology and Pediatrics at Emory University Schools of Public Health and Medicine, and a faculty member at the Emory Vaccine Center.

After adjusting for various factors, the Emory researchers observed that vaccine effectiveness for preventing MAARI was lower among patients taking statins compared with patients not on statins, particularly when flu was widespread in the state. The findings have potential implications for guidelines regarding statin use in older adults around the time of vaccination—but additional research, including studies examining laboratory-confirmed cases of flu, are needed, the authors noted.

Don’t stop statins or flu shots just yet

For now, should these results affect a physician’s care of patients? “Should statins be stopped for a period while influenza vaccine is administered? Should IIV [inactivated influenza vaccine] not be administered to statin users? In our opinion, the answer to all of these questions is no,” wrote Robert L. Atmar, MD, and Wendy A. Keitel, MD, of Baylor College of Medicine in Houston, in an accompanying editorial.

They added, “Instead, the results of these studies should be viewed as hypothesis generating and should prompt further investigations into whether statins reduce IIV immunogenicity and, if so, the mechanisms by which immune responses and associated VE are adversely affected.”

For more information visit the MDLinx Influenza Resource Center.

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