Infectious Diseases Society of America
A new pair of studies suggests that statins, drugs widely used to reduce cholesterol, may have a detrimental effect on the immune response to influenza vaccine and the vaccine's effectiveness at preventing serious illness in older adults.
Published inThe Journal of Infectious Diseases, the
findings, if confirmed by additional research, may have implications for flu
vaccine recommendations, guidelines for statin use around the time of vaccination,
and future vaccine clinical trials in seniors.
In one of the new studies, researchers analyzed immune response
data from an earlier flu vaccine clinical trial conducted during the 2009-2010
and 2010-2011 flu seasons.
In the new study, funded by Novartis Vaccines, which
also sponsored the original clinical trial, investigators focused on the
potential effect of statin use on patients' initial immune responses after
being immunized against flu. The analysis drew on data for nearly 7,000 adults
over the age 65 in four countries, including the United States.
Statin users had a significantly reduced immune response to vaccination compared to those not taking statins, as measured by the level of antibodies to the flu vaccine strains in patients' blood three weeks after being vaccinated, the researchers observed. The effect was most dramatic in patients on synthetic statins, rather than naturally derived statins.
"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 Dr. Steven
Black, MD, of Cincinnati Children's Hospital Medical Center and lead author of
the immune response study.
If confirmed, the findings could support the
preferential use of high-dose flu vaccine or vaccines containing adjuvants to
boost immune response in the elderly, in an attempt to counteract the apparent
effect, the study authors wrote.
A high-dose flu vaccine is approved for adults 65 and older in the
U.S., as are several standard-dose vaccines. Adjuvanted flu vaccines are
available in Europe and other countries but have not yet been licensed for use
in the U.S. The Centers for Disease Control and Prevention recommends that
everyone 6 months of age and older get a flu vaccine every season. Seniors are
at particular risk for serious illness and complications from flu, including
death.
In the other new study, conducted by researchers from Emory
University, the authors investigated the possible impact of statin therapy on
the effectiveness of flu vaccine at preventing serious respiratory illness.
The
researchers analyzed data spanning nine flu seasons from 2002 to 2011,
including information about flu vaccination, statin prescriptions, and cases of
medically attended, acute respiratory illness 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 Saad
B. Omer, MBBS, MPH, PhD, of Emory University and lead author of the vaccine
effectiveness study, which was financially supported by Emory and the National
Institute of Allergy and Infectious Diseases.
After adjusting for various factors, the Emory researchers
observed that vaccine effectiveness for preventing serious respiratory illness
was lower among patients taking statins compared to patients who were 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 studies, including research examining
laboratory-confirmed cases of flu, are needed first to provide more guidance,
the study authors noted.
The results from both new studies are biologically plausible and
raise important questions, but the findings should not yet affect how
physicians care for their patients, according to a related editorial commentary
by Robert L. Atmar, MD, and Wendy A. Keitel, MD, of Baylor College of Medicine
in Houston.
"Instead, the results of these studies should be viewed as
hypothesis-generating and should prompt further investigations into whether
statins reduce inactivated influenza vaccine immunogenicity and, if so, the
mechanisms by which immune responses and associated vaccine effectiveness are
adversely affected," the commentary authors wrote. The commentary
accompanies the two studies in The Journal of Infectious Diseases.
Fast Facts
- Statins are used by more than 40 percent of the U.S. population over the age of 65, according to the Centers of Disease Control and Prevention.
- In one study of flu vaccine recipients older than 65, statin users had a significantly reduced immune response to flu vaccination, compared to those not taking statins.
- In another study, vaccine effectiveness at preventing serious respiratory illness was lower among patients taking statins compared to patients who were not on statins.
- Additional research is needed to confirm the findings from both studies before potential changes in clinical practice are warranted.