One type of flu shot for older adults was more effective than another in preventing flu complications in older adults with risk factors, according to a study published Aug. 16 in Open Forum Infectious Diseases.
Findings show the MF59-adjuvanted trivalent influenza vaccine (aTIV) was more effective than the high-dose trivalent influenza vaccine (HD-TIV). Both vaccines are made for people 65 and older who have risk factors for serious flu complications. The MF59 vaccine contains an adjuvant, which is an immune-boosting agent that’s added to the shot.
Previous research suggested the vaccines had similar effectiveness in older adults, including those with a health condition known to heighten their risk for serious flu complications.
For this study, a team looked at electronic health record data on pharmacy and medical claims. They estimated the relative vaccine effectiveness (rVE) in more than 1.1 million people who took the aTIV vaccine and nearly 2.6 million people who took the HD-TIV vaccine from August 2019 through January 2020. Investigators measured how well the shot worked to prevent influenza-related medical encounters. The team also measured outpatient IRME, as well as flu- and pneumonia-related hospitalizations.
The team found that aTIV was more effective than HD-TIV to prevent any IRME in older adults with risk factors. In fact, aTIV had a 12.5% more effectiveness for adults with up to one risk factor on average, and 18.4% more effectiveness for adults with one or two risk factors. It carried a 10.4% rVE in those with three or more risk factors. There wasn’t a difference between shots in older adults with no risk factors.
Similar trends were seen with regard to hospitalizations for flu and pneumonia, with aTIV showing more effectiveness than HD-TIV, and no difference between shots in older adults with no risk factors.
The authors of the study said the adjuvant may be the reason for better effectiveness of aTIV in those who were more vulnerable to flu complications. The team would like to see more research on how the immune response generated by aTIV adds to overall vaccine effectiveness across different populations with varying risk factors.
