mRNA vaccines provide protection against most new variants of coronavirus infection, including the "delta" strain.
From November 2020 to January 2021, researchers collected blood samples from 40 health care workers before they received their first dose of Moderna or Pfizer. The researchers then took five blood samples from volunteers over 98 days, seven and 28 days after the first dose and seven, 28 and 70 days after the second.
Blood samples were exposed to 16 different variants of SARS-CoV-2 and measured antibody and T-cell production in response to the virus. An increased immune response was detected in all blood samples, although the strength of the response varied from person to person. The immune response to the "delta" variant was generally strong and increased after volunteers received second doses of vaccines. According to the researchers, cases of infection by the delta variant in vaccinated people were due to its extremely high infectivity, rather than to deficiencies in the vaccines. However, it was not it that most reduced the vaccine-induced immune response, but variants combining two mutations in the receptor-binding domain of the virus (E484K and N501Y/T) - the "beta" and "gamma" variants.
Also, the immune response was stronger in those who had had COVID-19 before vaccination. "Recovery after the initial infection is similar to the first dose of the vaccine," notes one immunobiology professor, Akiko Iwasaki. According to the researchers, this indicates that revaccination may be an effective measure to contain coronavirus infection.