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Am Fam Physician. 2024;109(4):372

Clinical Question

Is a high-dose recombinant influenza vaccine (FluBlok) more effective than a standard-dose vaccine in adults 50 to 64 years of age?

Bottom Line

Although there is a very small absolute reduction in the risk of influenza with high-dose recombinant vaccines, they have no impact on hospitalization. The recombinant vaccines may be less likely to have a mismatch due to antigenic drift from year to year, but this has not been proven because the match for both vaccines was relatively poor during the study years. (Level of Evidence = 1b−)


The study was a cluster randomized study (unmasked) set in the U.S. Kaiser Health System that compared a high-dose recombinant vaccine with standard-dose inactivated influenza vaccines. During the 2018/2019 and 2019/2020 influenza seasons (the 2020/2021 season was excluded), participating Kaiser sites were matched by size and randomly assigned to block A (high-dose vaccine in even-numbered weeks) or block B (high-dose vaccine in odd-numbered weeks). Ultimately, 632,962 patients received the high-dose recombinant vaccine and 997,366 received the standard-dose vaccine. Overall, 44% of the patients were men, 49% were non-White, and 74% had received the influenza vaccine the previous year. The authors used propensity score matching to adjust for differences between groups. They also used respiratory syncytial virus infection as a negative control because it was not expected to differ between groups. They report that the high-dose recombinant vaccine was 15% more effective (95% CI, 6.0% to 24.5%) in patients 50 to 64 years of age, but the actual number of cases of influenza confirmed by polymerase chain reaction testing was 2.0 cases per 1,000 people in the high-dose group and 2.34 cases per 1,000 people in the usual-dose group, or about one fewer case of influenza per 3,000 people. There was no difference in the important outcomes of hospitalization for influenza (0.34 vs. 0.39 per 1,000 persons; P = .19) or hospitalization for community-acquired pneumonia (0.38 vs. 0.46 per 1,000 people; P = .13). According to GoodRx, the retail price of FluBlok is $90 compared with approximately $30 for standard-dose inactivated vaccines.

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POEMs (patient-oriented evidence that matters) are provided by Essential Evidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, see Copyright Wiley-Blackwell. Used with permission.

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This series is coordinated by Natasha J. Pyzocha, DO, contributing editor.

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