Study strongly supports the CDC’s guidance that booster shots are appropriate for anyone ages 16 and older, and that mRNA vaccines are preferred.
An additional booster dose of the COVID-19 mRNA vaccines from Pfizer-BioNTech or Moderna is necessary to provide immunity against the omicron variant of SARS-CoV-2, according to a study published in Cell.
The omicron variant was identified in South Africa in late November 2021 and was found to be more transmissible than the preceding Delta variant. According to a press release, these study results suggest that traditional dosing regimens of COVID-19 vaccines available in the United States do not adequately produce antibodies capable of recognizing and neutralizing the Omicron variant.
Researchers investigated this issue by constructing a harmless version of the omicron variant known as a pseudovirus, which could be used in laboratory settings to evaluate the efficacy of COVID-19 vaccines. The pseudovirus mimicked the behavior of the omicron variant, which has 34 mutations in the spike protein that are not found in the original strain of SARS-CoV-2. According to the study, experts believe these mutations may be partially responsible for the virus’s rapid spread.
After creating the pseudovirus, the team acquired blood samples from 239 individuals who had been fully vaccinated with 1 of the 3 COVID-19 vaccines available in the United States. Samples included in the study were from 70 individuals who had received a third booster dose of either of the Pfizer or Moderna vaccine, according to CDC recommendations.
The samples were used to measure how effectively each vaccine induces protective antibodies against the omicron pseudovirus, as well as the delta and wild type viruses. According to the study authors, the results were very interesting.
“We detected very little neutralization of the omicron variant pseudovirus when we used samples taken from people who were recently vaccinated with 2 doses of mRNA vaccine or 1 dose of Johnson & Johnson,” Balazs said in the press release. “But individuals who received 3 doses of mRNA vaccine had very significant neutralization against the omicron variant.”
The researchers said they are not sure yet why the mRNA booster improved immune protection against the omicron variant, but one possibility is that an additional dose creates antibodies that bind more tightly to the spike protein, increasing their efficacy. Furthermore, a booster dose could generate antibodies that target regions of the spike protein that are common to all forms of SARS-CoV-2. Both of these theories could be true, according to the study authors.
Balazs noted that the 2-dose mRNA vaccine regimen, in addition to a booster dose, provides lower levels of neutralizing antibodies against the omicron variant than it does against the COVID-19 wild type strain or the delta variant. However, the study’s results strongly support the CDC’s guidance that booster shots are appropriate for anyone 16 years of age and older, and that mRNA vaccines are preferred.
Booster dose of mRNA COVID-19 vaccine is required for immune protection against Omicron variant of SARS-CoV-2. News release. Massachusetts General Hospital; January 6, 2021. Accessed January 7, 2022. https://www.massgeneral.org/news/press-release/Booster-dose-of-mrna-vaccine-required-for-immune-protection-against-omicron-variant