Statins, a group of drugs that act to reduce levels of fats in the blood, are commonly used by older adults seeking to lower blood cholesterol levels. High cholesterol is increasingly common in the elderly, who are also the most susceptible to the influenza virus. Although both health concerns warrant preventive treatment, two recent studies found that statins may reduce the overall effectiveness of flu vaccines in this population.
The studies were published in the Oct. 28 edition of the Journal of Infectious Diseases, and they discuss immune response data and how it is impacted by statin usage. A study conducted by researchers from the Cincinnati Children's Global Health Center and Novartis Vaccines (lead author Black, S.) analyzed immune response data from a clinical trial of trivalent influenza vaccine during the 2009-2010 and 2010-2011 flu seasons.
Throughout this study, which evaluated 7,000 adults older than 65 from the United States, Columbia, Panama and the Philippines, investigators reviewed antibody levels 3 weeks after flu vaccinations were administered.
A study by researchers at Emory University (lead author Omer, S.B.) examined flu vaccination statuses, statin prescriptions and medically attended acute respiratory illnesses. From the nearly 140,000 people analyzed, all of whom were enrolled in a large managed care group in Georgia, researchers were able to collect data from seven flu seasons ranging from 2002 to 2011.
Black et al found that statin users exhibited significantly reduced immune responses compared to those who did not use them. The researchers also concluded that reduced immune responses were more prominent in patients taking synthetic statins rather than naturally attained statins.
The difference between the two types of statins is that the synthetic drugs are made through chemical synthesis, whereas so-called natural statins are comprised of fungal compounds. Synthetic statins include the drugs atorvastatin, cerivastatin and fluvastatin, while natural options consist of the drugs lovastatin, pravastatin and simvastatin.
Similarly, Omer et al determined that vaccine effectiveness against serious respiratory infection was lowered in those taking statins, especially when the flu virus was circulating. The team noted that flu vaccine effectiveness in the elderly may be compromised if they are taking statins, compared to seniors who are not.
"Your immunologic response to pathogens diminishes over time, so to put it simply, as we age our ability to fight disease decreases," explained Glenn Hardesty, DO, an emergency medicine physician at Texas Health Arlington Memorial Hospital. "This means that older people's bodies don't respond to the vaccines as well as they did in the past."
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These results come as a consequence of the two different methods of prevention having opposing effects on inflammation. Statins seek to improve cardiac health by lowering inflammation levels in blood vessels, whereas flu vaccines prime the body to fight influenza virus through inflammation. Therefore, statins and flu vaccinations have contradicting inflammatory outcomes and, when given together, inhibit optimal results.
In response to these findings, some researchers have suggested that older people who use statins should receive a higher dose of the flu vaccine in order to better protect their immune systems from the virus. According to a study published in the New England Journal of Medicine,the high-dose vaccine is 24.2% more effective in preventing flu in adults 65 and older relative to a standard-dose vaccine.
"High-dose flu vaccine is an important advance and overcomes some of the deficits of an older immune system. It may also overcome some of the effects of statin therapy," said Amesh A. Adalja, MD, senior associate at the University of Pittsburgh Medical Center's Center for Health Security.
While high-dose vaccines may be an applicable alternative, experts advise against terminating prescribed statins. They caution that more research is needed to fully understand this issue, and while flu vaccine effectiveness can be critical, statins still have much success in lowering the risk of cardiovascular events.
Lindsey Nolen is a staff writer. Contact: firstname.lastname@example.org.