Recombinant Influenza Vaccine Safe, Effective Among Seniors
A quadrivalent, recombinant influenza vaccine (RIV4) is safe and provides better protection than a standard-dose, egg-grown, quadrivalent, inactivated influenza vaccine (IIV4) against influenza-like illness among adults aged 50 years or older, a new study shows.
The study results are very encouraging; however, the "absolute differences in laboratory-confirmed influenza infections between the RIV4 and the standard IIV4 were small," Walter A. Orenstein, MD, DSc (Hon), associate director of the Emory Vaccine Center and professor of medicine, pediatrics, and global health at Emory University, Atlanta, Georgia, told Medscape Medical News.
Lisa M. Dunkle, MD, from Protein Sciences, Meriden, Connecticut, and colleagues published the results of their study in the June 22 issue of theNew England Journal of Medicine.
"The cumulative incidence of [reverse-transcriptase polymerase-chain-reaction (RT-PCR)]-confirmed influenza-like illness showed significant efficacy of RIV4 over IIV4 throughout the influenza season (hazard ratio, 0.69; 95% [confidence interval (CI)], 0.53 to 0.90; P=0.006)," the authors write.
During the 2014 to 2015 influenza season in the United States, circulating strains of influenza A(H3N2) viruses were antigenically and genetically different from the 2014 to 2015 vaccine strain.
This mismatch resulted in a lower than usual vaccine effectiveness in adults aged 50 years or older, and thus a higher than usual rate of influenza-associated hospitalizations among adults aged 65 years or older.
Better vaccines are needed to reduce the burden of influenza on public health, and the authors emphasize that using a recombinant vaccine could help achieve this goal.
The researchers conducted a randomized, double-blind, multicenter, phase 3-4 trial to compare the efficacy of RIV4 with IIV4 against influenza-like illness in older adults.
They enrolled 9003 adults who were 50 years of age or older and randomly assigned them to receive a single dose of either RIV4 or IIV4 at one of 40 outpatient centers across the United States. After vaccination, participants were asked to return to their trial site if they developed influenza-related respiratory symptoms (such as cough, sore throat, or difficulty breathing) or systemic symptoms (such as fever, chills, or myalgia).
Patients who had at least one symptom in both the respiratory and systemic illness categories underwent influenza testing. The researchers collected a nasopharyngeal swab from these patients within 72 hours after the onset of symptoms, and used RT-PCR and virus culture to confirm a diagnosis of influenza infection.
The full analysis included 8963 adults, and 8672 (96.8%) of these with postvaccination data made up the safety population.