Enhanced influenza vaccines elicit greater antibody responses compared with standard-dose vaccine in older adults, findings from a systematic review and meta-analysis showed.
“In order to address the poorer immunogenicity of influenza vaccines in older adults, a number of new and potentially enhanced vaccines have been developed in recent years,” researchers wrote in The Journal of Infectious Diseases. “These include the addition of adjuvants to vaccines, the inclusion of higher antigen content and the administration of intradermal vaccines.”
The researchers searched PubMed, Medline and Embase for studies published through Dec. 31, 2017, of improvements in antibody responses as measured by hemagglutination inhibition (HAI) assay associated with enhanced vaccines compared with standard-dose vaccine. They included 39 randomized controlled trials in the study.
According to the trials, adults aged 60 years or older who received enhanced vaccines experienced significantly higher post-vaccination titers for all vaccine strains and higher proportions with elevated titers of 40 or greater for most vaccine strains when compared with adults of the same age receiving standard-dose vaccines. The difference was “most notable” for influenza A(H3N2), a strain that causes relatively severe illness, with high-dose vaccine producing an 82% higher post-vaccination titer to the strain compared with standard-dose vaccine, the researchers reported.
“This was significantly higher than 52% estimated for MF59-adjuvantated vs. standard dose vaccines (P = .04), which was higher than 32% estimated for intradermal vs. standard-dose vaccines (P < .01),” they wrote.
The review showed “a comparable immunogenicity profile among each of the enhanced seasonal influenza vaccines against vaccine strains/lineages when measured by HAI titers at 30 days after vaccinations,” they wrote. “Post-vaccination [geometric mean titers] were significantly higher for enhanced vaccines compared to [standard-dose] vaccine for all vaccine strains we could examine.”
The researchers said head-to-head immunogenicity and efficacy trials of enhanced influenza vaccines “would be very informative, particularly if conducted across multiple years to provide data on efficacy against a variety of circulating strains, and to provide data on immune responses to repeated vaccinations with enhanced vaccines.” – by Bruce Thiel
Disclosures: Please see the study for a list of all authors’ relevant financial disclosures.