Vaccine efficacy substantially higher against severe disease than against infection; no evidence seen for declining protection against severe disease
WEDNESDAY, Sept. 15, 2021 (HealthDay News) — Although providing COVID-19 vaccine boosters could be appropriate for some individuals and may ultimately be needed, the current evidence suggests that vaccine efficacy is high against severe disease, with no evidence of declining protection, according to a viewpoint article published online Sept. 13 in The Lancet.
Philip R. Krause, M.D., from the U.S. Food and Drug Administration in Silver Spring, Maryland, and colleagues discuss considerations in boosting COVID-19 vaccine immune responses by offering booster doses for vaccinated populations.
The authors note that boosting could be appropriate for some individuals in whom the primary vaccination series might not have induced adequate protection. Furthermore, boosting might ultimately be needed in the general population due to waning immunity of primary vaccination or variants expressing antigens that have evolved to the extent that the original vaccine antigens no longer provide adequate protection. However, there could be risks if boosters are introduced too soon or too frequently, including immune-mediated side effects or adverse reactions to unnecessary boosting, which could impact vaccine acceptance. Based on randomized trials, vaccine efficacy is substantially greater against severe disease than against infection and is protective against all main viral variants, including the delta variant. Even if humoral immunity appears to wane, it does not necessarily predict reductions in vaccine efficacy over time. To date, no careful observational studies have provided credible evidence for substantially declining protection against severe disease. Even in populations with high vaccination rates, the unvaccinated are the major drivers of transmission and are at highest risk for serious disease.
“Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated,” the authors write. “If vaccines are deployed where they would do the most good, they could hasten the end of the pandemic by inhibiting further evolution of variants.”
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