By Bill Hathaway, Yale University — MedicalXPress — 11 October 2021
Two of the commonly used coronavirus vaccines provide protection against multiple variants of the virus that causes COVID-19, including the highly infectious Delta variant, according to a new Yale study published in the journal Nature. “Vaccines induce high levels of antibodies against Delta and most variants. And two shots are better than one,” said co-corresponding author Akiko Iwasaki, Waldemar Von Zedtwitz Professor of Immunobiology. The study collected blood samples from 40 healthcare workers at Yale New Haven Health System between November 2020 and January 2021, before vaccination, then periodically after receiving their first and second doses of the Moderna or Pfizer-BioNTech mRNA vaccines. The blood samples were then exposed to 16 different SARS-CoV-2 variants, including Delta, and both antibody and T-cell responses were measured.
The researchers found evidence of enhanced immune system response in all blood samples, with the immune response to the Delta variant being generally robust — and even stronger in samples collected after individuals’ second shots. Breakthrough cases attributed to the Delta variant are unlikely to arise from vaccine failure: “The Delta variant is more infectious than earlier variants. The high transmissibility of the variant, not its escape from our vaccine-induced immune response, best explains infections among the vaccinated,” said co-author Nathan Grubaugh. Additionally, those who had been infected with COVID-19 prior to vaccination exhibited a more robust immune response to all variants than those who were uninfected and fully vaccinated — “recovering from an initial infection is like getting a first vaccine shot,” Iwasaki said. The results suggest booster shots can have a similar immune-boosting effect.