Pfizer/BioNTech and Moderna vaccines induce T-cell immunity against SARS-CoV-2

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Researchers in the United States have shown that the Pfizer/BioNTech and Moderna messenger RNA (mRNA) vaccines are effective at generating T-cell immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent that causes coronavirus disease 2019 (COVID-19).
The team found that vaccinated individuals developed robust T-cell responses to the SARS-CoV-2 spike protein that the virus uses to bind to and infect host cells.

The researchers – from Massachusetts General Hospital and Harvard Medical School in Boston – report that the T-cell response increased significantly from baseline after just one vaccine dose. After a second dose, the response was more potent than in a convalescent cohort.

However, Marcela Maus and colleagues also found 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 says it will be important to determine how T-cell immunity impacts the aggregate immune response to the variants and whether a reduced T-cell response translates to adverse clinical outcomes.

A pre-print version of the research paper is available on the bioRxiv* server, while the article undergoes peer review.

Concerns have arisen regarding vaccine efficacy against variants

As of January 2021, the Pfizer/BioNTech and Moderna COVID-19 vaccines that are designed to elicit a humoral (antibody) response against the SARS-CoV-2 spike protein were authorized for emergency use by the U.S. Food and Drug Administration.

Following the completion of Phase 3 clinical trials, the Pfizer-BioNTech vaccine was reported to be 95% effective at preventing symptomatic COVID-19, while the Moderna vaccine was reported to be 94.1% effective.

However, since the first cases of SARS-CoV-2 were first identified in Wuhan, China, in late December 2019, several new variants have emerged. These new viral lineages contain mutations that have been shown to increase transmissibility and help the virus to escape the antibody response generated by vaccination.

"The emergence of more transmissible and virulent SARS-CoV-2 variants, coinciding with evidence of escape from neutralizing antibodies to the wild-type virus, raises concerns regarding…
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