“There’s been great concern about the new Omicron variant of SARS-CoV-2, the coronavirus that causes COVID-19. A major reason is Omicron has accumulated over 50 mutations, including about 30 in the spike protein, the part of the coronavirus that mRNA vaccines teach our immune systems to attack. All of these genetic changes raise the possibility that Omicron could cause breakthrough infections in people who’ve already received a Pfizer or Moderna mRNA vaccine.
So, what does the science show? The first data to emerge present somewhat encouraging results. While our existing mRNA vaccines still offer some protection against Omicron, there appears to be a significant decline in neutralizing antibodies against this variant in people who have received two shots of an mRNA vaccine.
However, initial results of studies conducted both in the lab and in the real world show that people who get a booster shot, or third dose of vaccine, may be better protected. Though these data are preliminary, they suggest that getting a booster will help protect people already vaccinated from breakthrough or possible severe infections with Omicron during the winter months.” quoted from the NIH Directors Blog
