Researchers from the USA have shown that mRNA vaccines, Pfizer/BioNTech, and Moderna are effective at generating T-cell immunity against SARS-CoV-2. The study published on a pre-print server revealed that vaccinated individuals had diminished T-cell responses against the SARS-CoV-2 variants that emerged in the U.K. (B.1.1.7), South Africa (B.1.351), and Brazil (P1).
The team used two standardized assays to measure T-cell immunity to the wild-type and variant SARS-CoV-2 spike proteins in peripheral blood samples taken from 29 vaccinated, previously uninfected individuals and 25 convalescent individuals who had recovered from mild COVID-19. In the vaccinated individuals (11 Pfizer/BioNTech, 18 Moderna), the T-cell response was measured before inoculation, and then at a median of 22 days (range 16–30 days) following a first dose and at a median of 59 days following the first dose (range 38–204 days) when all vaccinees had also received a second dose.
The team reports that T-cell responses to the wild-type spike protein increased significantly from baseline after an initial vaccine dose, even as soon as 7 days following immunization. Following a second dose, the median spike-specific T cell responses were higher in the vaccinees than in the convalescent individuals. The T-cell response to pools of the spike variants B.1.1.7, B.1.351, and P.1 among vaccinated individuals was decreased to 84.6% of the response to wild-type spike for the B.1.1.7 lineage, to 70.2% for the B.1.315 lineage, and 83.4% for the P.1 lineage.
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