Mutations have led to several new, concerning coronavirus variants, including the B.1.1.7 (Alpha) variant, which was first detected in the United Kingdom; the B.1.351 (Beta) variant, which originated in South Africa; the P.1 (Gamma) variant, which originated in Brazil, and the B.1.617.2 (Delta) variant, which was first documented in India. Emerging evidence suggests that the current vaccines are effective against at least some of these variants.
Two peer-reviewed and published studies have found the Pfizer/BioNTech vaccine to be extremely effective against the Alpha and the Beta variants. The first study, published in NEJM, looked at data from more than 200,000 people from the country of Qatar between early February and late March 2021. During that time, the Alpha and Beta variants were responsible for nearly all COVID cases in that country. The researchers found that in people who were fully vaccinated, the Pfizer vaccine was 97.4% effective at preventing severe, critical, or fatal disease caused by the Alpha or Beta variants.
The second study, published in The Lancet, looked at more than 200,000 COVID infections in Israel from late January to early April 2021, when the Alpha variant accounted for more than 90% of infections. The researchers found that in fully vaccinated people, the Pfizer vaccine was nearly 97% or more effective at preventing symptomatic COVID-19, COVID-related hospitalization, severe or critical COVID-19, or COVID-related death.
Newer research has also found the Pfizer/BioNTech vaccine to be effective against the Delta variant, which is now the dominant variant in the US. A study from Public Health England found that full vaccination with the Pfizer/BioNTech vaccine was 88% effective at protecting against symptomatic illness caused by the Delta variant, and 96% effective at preventing hospitalization due to the Delta variant.
Studies on the effectiveness of the Moderna vaccine are ongoing. In the lab, it has performed well against the Alpha variant, compared to the original, unmutated virus. However, it was less effective against the Beta and Delta variants compared to the unmutated virus and the Alpha variant. More study is needed to see if the laboratory results hold up in real-world conditions.
It's important to remember that both the Pfizer/BioNTech and Moderna vaccines are extremely effective — 95% and 94.1%, respectively. Even with some possible decrease in effectiveness against variants, they will still provide excellent protection against severe illness.
Another study, published in Nature, looked at blood samples from people who received the Johnson & Johnson adenovirus vaccine. It found that the vaccine produced a less robust antibody response against the Beta and Gamma variants compared to the response to the original SARS-CoV-2 virus. However, the T cell immune response held up, particularly among the type of T cells that prevent the virus from spreading within the body. This immune response should protect against developing severe symptoms if a person does get infected. Johnson & Johnson also released data from a small, unpublished laboratory study, which found a strong neutralizing antibody response against the Delta variant in people who had received the single-shot J&J vaccine. The response was sustained for at least eight months, the duration of the study.