Indications are building that while the Omicron variant of coronavirus is very contagious, it may cause a milder course of disease than Delta does, Dr. Anthony Fauci said Wednesday.
“We know now, incontrovertibly, that this is a highly, highly transmissible virus. We know that from the numbers we're seeing,” Fauci, director of the National Institute of Allergy and Infectious Diseases, said at a White House Covid-19 briefing.
“And clearly, there is a degree of immune evasion, particularly against infection and, to some degree, against hospitalization,” he added.
Omicron can infect vaccinated people, though not as easily as it infects unvaccinated people, and certain monoclonal antibody treatments do not help against it.
“However, importantly, and the bottom line message here, is that boosters bring back up that degree of protection to a level that is approximately what it was before. So boosters are critical in getting our approach to Omicron to be optimal,” Fauci said.
Several studies from South Africa and the UK, as well as lab studies in animals, indicate that the Omicron variant may cause less severe disease, Fauci said. In Britain, the risk of hospitalization admission for Omicron was 40% that of the risk seen with Delta.
“In the United States, we are getting an accumulation of data,” Fauci added. “The spike in cases is out of proportion to the increase in hospitalization.”
He said that over 14 days in December, the US racked up a 126% increase in the number of cases but just an 11% increase in hospitalizations.
“Now, we must remember that hospitalizations and deaths are lagging indicators,” Fauci noted. “However, the pattern and disparity between cases and hospitalizations strongly suggest that there will be a lower hospitalization-to-case ratio when the situation becomes more clear.
“So in conclusion, the data are encouraging but still in many respects preliminary,” Fauci noted. “But having said this, all indications point to a lesser severity of Omicron versus Delta. It is difficult to determine what degree of lessened severity is due to pre-existing immunity or the intrinsically lower virulence of Omicron — as suggested by the animal studies — or a combination of both.”
And the sheer numbers could still mean that, even with lower hospitalization rates for Omicron, the number of people infected could add up to more people in the hospital and a strain on the nation’s health care system, Fauci noted.