Taking statins may reduce the vaccine efficacy against the A(H3N2) strain of the influenza virus, according to a recent study published in the Journal of Infectious Diseases. However, vaccine effectiveness for A(H1N1)pdm09 or type B strains of influenza was not affected.
Huong Q. McLean, PhD, MPH, of the Center for Clinical Epidemiology and Population Health at the Marshfield Clinic Research Foundation in Marshfield, Wisconsin and colleagues examined 3285 adults ≥ 45 years old with acute respiratory illness for 10 consecutive influenza seasons beginning in 2004-2005 and ending 2014-2015.
The researchers noted that earlier studies had shown that statins have proven anti-inflammatory effects, and older adults who usually take these medications are also more at risk for complications from influenza.
Patients were prospectively enrolled in the study, and divided into four groups: 1217 vaccinated patients who did not use statins (37%), 903 unvaccinated patients who did not use statins (27%), 847 (26%) vaccinated patients taking statin medication and 318 unvaccinated patients taking statin medication (10%). Researchers noted that vaccination was confirmed for patients through a vaccine registry.
Dr McLean and colleagues reported “Statin use modified vaccine effectiveness and influenza risk for A(H3N2) infection (P=.002), but not for A(H1N1)pdm09 or B (P=.2 and .4, respectively). Vaccine effectiveness against A(H3N2) was 45% (95% confidence interval [CI]: 27, 59) among statin nonusers and -21 (CI: -84, 20) among statin users. Vaccinated statin users had significant protection against A(H1N1)pdm09 (68%, CI: 19, 87) and type B (48%, CI: 1, 73).”
There were differences in hemagglutination inhibition (HI) titers between statin users and nonusers, with results much lower in patients taking the medication. In addition, Dr McLean and colleagues reported that the A(H3N2) geometric mean antibody titer (GMT) was 40% lower in patients taking statins. There was also 28% lower GMT against type B and A(H1N1)pdm09 but the researchers noted that “postvaccination titers against A(H3N2) in statin users were substantially higher than the regulatory threshold for seroprotection (1:40),” and that “statin-using adults who were seronegative at baseline had decreased immune response to A(H3N2) and type B, but not A(H1N1)pdm09.”
However, the investigators explained that the serologic response doesn’t fully explain why there is a decrease in VE for A(H3N2) for statin users.
“The biological basis for differential strain effects by subtype is uncertain. Further research is needed to confirm these findings and explore potential mechanisms for statin-induced effects on vaccine response and influenza severity,” Dr McLean and colleagues concluded.