Créditos: Comité científico CovidLeer más
Late last year, UK health authorities announced that the second dose of authorized COVID-19 vaccines would be administered up to 12 weeks instead of 3 to 4 weeks after the first dose. The change was intended to free up initial doses for more people, but it also created an opportunity to investigate a vaccine schedule that hadn’t been tested in clinical trials.
One resulting study, which has not yet been peer reviewed, found greater vaccine efficacy when the first and second BNT162b2 (Pfizer-BioNTech) vaccine doses were given more than 6 weeks apart. Another study, recently published in Cell, analyzed immune responses 4 weeks after the second BNT162b2 shot was administered to almost 600 UK health care workers, most of whom received the long-dosing regimen.
In the latter study, neutralizing antibody levels were higher after a 6- to 14-week dosing interval than after a 2- to 5-week interval, although the wait made less of a difference for workers with prior SARS-CoV-2 infections.
Compared with the short-interval group, SARS-CoV-2 spike protein-specific B-cell responses were about 7 times higher among participants in the long-interval group who hadn’t been previously infected. T-cell responses were robust in both groups, although infection-naive participants in the extended dosing group had fewer of a certain T-cell subset.
“When community levels of circulating SARS-CoV-2 virus are low, the extended dosing interval appears to be suitable for immunogenicity, but this needs to be weighed against the more immediate benefits of two doses over one,” the authors wrote.
They cautioned that participants’ responses were highly variable, so the findings are more relevant on a population level than an individual level. Ongoing studies will measure how long the workers’ immune responses persist after the extended regimen.
Créditos: Comité científico Covid