The SARS-CoV-2 Omicron variant harbors 34 mutations in the spike than other variants. It can potentially escape vaccine-induced humoral immunity.
People are desperate to know whether the current vaccines protect against Omicron. To find the answer, scientists at the Ragon Institute of MGH, MIT, and Harvard measured the neutralization potency of COVID-19 vaccines.
Scientists, at first, constructed a harmless version of Omicron known as a “pseudovirus.” Next, they collected 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 health care system and residents of Chelsea, Massachusetts, a community with a high rate of COVID-19 infections.
70 men and women in this group had received a booster dose of either the Pfizer or Moderna vaccine, as recommended by the Centers for Disease Control and Prevention.
Scientists then used blood samples to measure the effectiveness of each vaccine in producing antibodies against the Omicron pseudovirus, as well as the Delta and wild-type viruses. The results were striking.
Alejandro Balazs, whose laboratory at the Ragon Institute, said, “We detected very little neutralization of the Omicron variant pseudovirus when we used samples taken from people who were recently vaccinated with two doses of mRNA vaccine or one dose of Johnson & Johnson. But individuals who received three doses of mRNA vaccine had very significant neutralization against the Omicron variant.”
In simple words, an additional “booster” dose of Moderna or Pfizer mRNA-based vaccine is needed to provide immunity against the Omicron variant of SARS-CoV-2, suggests the study. It is essential as the traditional dosing regimens of COVID-19 vaccines do not produce antibodies capable of recognizing and neutralizing the Omicron variant.
Wilfredo F. Garcia-Beltran, a clinical pathology resident at MGH, said, “It’s not yet clear why an mRNA booster dramatically improves immune protection against Omicron, but one possibility is that an additional dose creates antibodies that bind more tightly to the spike protein, increasing their effectiveness. Also, a booster dose may generate antibodies that target regions of the spike protein that are common to all forms of SARS-CoV-2. Both theories may be true.”
Balazs said, “Three-dose mRNA vaccine regimen — that is, the traditional two doses and a booster of Pfizer or Moderna vaccines — provides somewhat lower levels of neutralizing antibodies against Omicron than it does against the COVID-19 wild type strain or Delta variant. But the study’s results strongly support the CDC’s advice that COVID-19 booster shots are appropriate for anyone 16 and older and those mRNA vaccines are preferred.”
- Wilfredo F. Garcia-Beltran et al. mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against SARS-CoV-2 Omicron variant. DOI: 10.1016/j.cell.2021.12.03