An additional “booster” dose of Moderna or Pfizer mRNA-based vaccine is needed to provide immunity against the Omicron variant of SARS-CoV-2, the virus that causes COVID-19, according to a study by researchers at the Ragon Institute of MGH, MIT and Harvard. The results of this study, reported in the journal Cell, indicate that traditional dosing regimens of COVID-19 vaccines available in the United States do not produce antibodies capable of recognizing and neutralizing the Omicron variant.

In late November, health officials in South Africa reported that a previously unknown variant of SARS-CoV-2 was rapidly spreading throughout the country. The variant, given the name Omicron by the World Health Organization, would soon prove to be far more transmissible than Delta, the variant that previously had caused the majority of COVID-19 infections. “People desperately wanted to know whether current vaccines protect against Omicron,” says the senior author of the Cell paper.

To find answers, Balazs collaborated with a team that included the lead author of the Cell paper, Wilfredo F. Garcia-Beltran, MD, a clinical pathology resident at MGH and a clinician-scientist fellow at the Ragon Institute. The first step was to construct a harmless version of Omicron known as a “pseudovirus” that could be used in the laboratory to evaluate the effectiveness of the three COVID-19 vaccines available in the United States, which include the two-dose Pfizer and Moderna injections and the one-dose Johnson & Johnson vaccine. The pseudovirus that Balazs and colleagues created mimicked the behavior of Omicron, which has 34 mutations on its “spike” protein that are not found on the original strain of SARS-Cov-2 first detected in Wuhan, China, in December 2019. Scientists believe that these mutations may be partially responsible for Omicron’s rapid spread throughout the world.

Next, Garcia-Beltran worked with colleagues at MGH, including hematology-oncology fellow Vivek Naranbhai, MD, PhD, to acquire blood samples from 239 individuals who had been fully vaccinated with one of the three COVID-19 vaccines. The study subjects included employees within the Massachusetts General Brigham healthcare system and residents of Chelsea, Massachusetts, a community with a high rate of COVID-19 infections. “It was important to us to have a diverse population represented in the study,” says Garcia-Beltran. Included in this group were 70 men and women who had received a third booster dose of either the Pfizer or Moderna vaccine, according to recommendations by the Centers for Disease Control and Prevention.

Release date: 06 January 2022
Source: Massachusetts General Hospital