Recombinant flu vaccine appears to provide benefit in patients ages 50 to 64 years
An industry-funded study compared a high-dose recombinant influenza vaccine with one of two standard-dose egg-based vaccines over two flu seasons and found patients who received a high-dose vaccine were less likely to test positive for flu.
Patients ages 50 to 64 years may benefit from immunization with a high-dose recombinant flu vaccine, a recent industry-funded study found.
Researchers at Kaiser Permanente Northern California performed a cluster-randomized observational study in which a high-dose recombinant influenza vaccine (Flublok Quadrivalent) or one of two standard-dose egg-based influenza vaccines was routinely administered during the 2018-2019 and 2019-2020 influenza seasons to adults ages 50 to 64 years and those ages 18 to 49 years. Flublok Quadrivalent is one of three higher-dose or adjuvanted vaccines recommended preferentially for adults ages 65 years and older by the CDC's Advisory Committee on Immunization Practices (ACIP). For adults ages 18 to 64 years, ACIP does not recommend one flu vaccine over another.
The study's primary outcome was influenza confirmed by polymerase chain reaction (PCR) testing, while secondary outcomes included PCR-confirmed influenza A, PCR-confirmed influenza B, and hospitalization related to PCR-confirmed influenza. Cox regression analysis was used to estimate the hazard ratio of the recombinant vaccine versus the standard-dose vaccines for each outcome. Sanofi, the manufacturer of Flublok Quadrivalent, funded the study, which was published Dec. 14 by the New England Journal of Medicine.
Overall, 1,630,328 patients ages 18 to 64 years were included in the study, 632,962 who received the recombinant vaccine and 997,366 who received a standard-dose vaccine. Fifty-six percent were women, 51% were White, and 74% had received an influenza vaccine in the previous year. There were 675,252 patients ages 50 to 64 years, 279,400 of whom (41.4%) received the recombinant vaccine and 395,852 of whom (58.6%) received a standard-dose vaccine. Among 955,076 patients between ages 18 and 49 years, 353,562 (37.0%) received the recombinant vaccine and 601,514 (63.0%) received a standard-dose vaccine.
A total of 1,386 cases of PCR-confirmed influenza were diagnosed in the recombinant vaccine group and 2,435 cases in the standard-dose group during the study period. In patients ages 50 to 64 years, 559 of those who received a recombinant vaccine tested positive for influenza versus 925 who received a standard-dose vaccine (2.00 vs. 2.34 cases per 1,000, respectively; relative vaccine effectiveness, 15.3% [95% CI, 5.9% to 23.8%]; P=0.002); relative vaccine effectiveness against influenza A specifically was 15.7% (95% CI, 6.0% to 24.5%) in this age group (P=0.002). No difference was seen in the outcome of influenza-related hospitalization between those who received the recombinant vaccine versus a standard-dose vaccine.
The authors noted that the number of participants in the two groups differed and that they looked at only two influenza seasons, among other limitations. They concluded that the high-dose recombinant vaccine was more protective against PCR-confirmed influenza than an egg-based standard-dose vaccine in adults ages 50 and 64 years. “If standard-dose vaccines were already preventing most cases of influenza and breakthrough cases were uncommon, preventing 15% of breakthrough cases would be of modest public health benefit,” the authors wrote. “However, since standard-dose vaccines prevent at most 40 to 60% of influenza cases annually, reducing the incidence of breakthrough influenza by 15% would provide a substantial public health benefit, especially during more severe influenza seasons.”
In related news, the CDC issued a Health Alert Network Health Advisory on Dec. 14 to alert clinicians to low vaccination rates against influenza, COVID-19, and respiratory syncytial virus (RSV) so far this season. Clinicians should administer influenza, COVID-19, and RSV immunizations now to patients, if recommended, and should recommend antiviral medications for influenza and COVID-19 for all eligible patients, especially patients at high-risk of progression to severe disease, the CDC said.