Healthy individuals who have been vaccinated, and especially those who have been boosted, appear unlikely to develop severe infections from the omicron variant that would land them in the hospital, say medical experts who have monitored the effects of the newest coronavirus variant since it was identified over four weeks ago.
While omicron has sent U.S. infections soaring to levels not seen since last winter’s wave, it appears to have less severe effects than the delta variant, according to a handful of international studies and early data from several U.S. hospitals.
Those infected by the omicron variant are 15 to 20 percent less likely to go to an emergency room, and 40 percent less likely to be hospitalized overnight, compared with those infected with delta, according to English data analyzed by scientists from Imperial College London. That aligns with early U.S. data from some hospitals.
At the Houston Methodist hospital system, about 15 percent of symptomatic individuals have ended up hospitalized — about a 70 percent reduction compared with those infected by the delta variant, said James Musser, chair of pathology and genomic medicine.
A separate study from Britain, which is not yet peer-reviewed, found that people infected with omicron were almost 60 percent less likely to enter the hospital than those infected with delta.
“What is absolutely clear is there is a lower rate of hospitalization with our omicron patients in our hospital system,” Musser said. “That does not necessarily mean that this variant is quote-unquote ‘less virulent.’ The jury’s still out on that. What we know now is that … if you are immunized and, more importantly, if you are boosted, you’re going to stay out of substantial trouble.”
He and other experts warn against complacency, however, cautioning that millions of Americans, particularly the unvaccinated, remain vulnerable to more serious disease from the most transmissible coronavirus variant to date.
Other factors that might lead to greater risk include an individual’s age, the type of vaccine or booster they received, and whether they have underlying health problems, such as heart disease or obesity, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota and a member of President Biden’s covid-19 transition task force.
“Have you previously had infection? Were you vaccinated? How many doses of vaccine, and was it more than six months ago? So in some ways this is almost like a calculus problem. It’s got a lot of moving parts to it and we’re trying to figure it out,” Osterholm said.
Doctors also caution that far more people will become infected with omicron simply because of its transmissibility. If even a small fraction of those land in the hospital, they worry that health-care systems that are already short-staffed because of delta infections could be overwhelmed — with potentially dire results for those needing critical care as a result of car accidents, heart attacks, strokes, or any number of things that bring people to emergency rooms.
“We need to be respectful of the fact that our hospital system has been under this kind of duress for such a long time,” said Larry Corey, a virologist at the Fred Hutchinson Cancer Research Center in Seattle. “We need to do everything we can to not allow the situation, where there’s such crowding and such intensity that we can’t optimally take care of the people who get severe disease.”
Anthony S. Fauci, Biden’s chief medical adviser, said the rapid increase in the numbers of people getting infected with the omicron variant will invariably put additional strain on the system.
“We’re going to have a real challenge to the health-care delivery system — namely the number of beds, the number of ICU beds and even the number of health-care providers,” Fauci said in an interview. “Even vaccinated people are getting breakthrough infections. So if you get enough nurses and doctors infected, they are going to temporarily be out of action. And if you get enough of them out of action, you could have a double stress on the health-care system.”
The welcome news for most people who are vaccinated and boosted is that omicron infections often mimic the symptoms of the common cold. Those with two shots of vaccine, but no booster, also appear to fare relatively well, though they may develop more intense symptoms that may last longer, experts said.
Of the 205 million Americans who have been vaccinated, about 66 million, or 32 percent, have received a booster dose, according to the Centers for Disease Control and Prevention.
In a series of Twitter posts, Craig Spencer, who teaches emergency medicine at Columbia University Medical Center, said every boosted patient he has seen in the emergency room has had no difficulty breathing or shortness of breath. Those who have had two doses of either the Pfizer or Moderna vaccines also have had mild symptoms, he said, “but more than those who had received a third dose.”
But almost every patient who had to be hospitalized was unvaccinated, he said.
“No matter your political affiliation, or thoughts on masks, or where you live in this country, as an ER doctor you’d trust with your life if you rolled into my emergency room at 3am, I promise you that you’d rather face the oncoming Omicron wave vaccinated,” Spencer wrote.
Children are also filling up hospital beds in many parts of the country, especially in New York. State officials issued a warning on Christmas Eve after a fourfold increase in hospitalizations in children under 18 in New York City between Dec. 5 and last week. About half of the admissions were children under 5, who are not eligible for vaccination, according to the New York Department of Health.
Experts cautioned that those at higher risk of severe infection to previous variants probably remain vulnerable to this one.
It’s not yet clear whether older, boosted individuals and those with underlying conditions, such as diabetes and heart disease, face the same lowered risk with omicron. Answering such questions is key to assessing the likely trajectory of the variant in the United States because the nation’s population is older and less healthy than those of many of its global peers.
So far, though, early U.S. data echoes what has been seen in South Africa and Britain, where omicron waves are slightly ahead of this country’s.
A group of Scottish scientists said recently that vaccinated people appear to have some protection against symptomatic infection from omicron, although less than they did against delta. A third dose or booster of an mRNA vaccine was associated with a 57 percent reduction in the odds of developing a symptomatic omicron case.
In the Johns Hopkins Hospital emergency department, physicians are seeing more infections than at any other point in the pandemic, but most of the cases are not severe, said Stuart Ray, a professor of medicine in the division of infectious diseases. But he warned that there is not yet “reassuring evidence” the United States will be spared from a disruptive wave of infections and complications.
The country faces other challenges with omicron in terms of its medicine cabinet. Two of the three existing intravenous treatments called monoclonal antibodies — those from Regeneron and Eli Lilly — do not work against the variant. Some Republican governors had touted the ability of those with covid-19 to receive monoclonal antibodies, spurring some Americans to see those treatments as an alternative to getting vaccinated.
The only monoclonal antibody that does work, sotrovimab from Vir Biotechnology and GlaxoSmithKline, is in short supply and will not be available to many of those who become infected. The Food and Drug Administration authorized two easy-to-take antiviral pills last week and one has high efficacy against omicron, but it will be in initial short supply. Distribution of the pills is expected to begin shortly.
It is also unclear whether the surge in the United States will follow the same pattern as South Africa’s, which rapidly passed the peak of omicron cases last week.
South Africa’s population is significantly younger and has far lower vaccination rates, with about 35 percent of the population immunized, and virtually no one boosted. The country also grappled with a delta variant wave that infected a far greater portion of the population than it did in the United States.
The significant number of South African residents infected with delta compared with the United States could prove to be an important distinction that might make more Americans vulnerable to omicron, said Chris Beyrer, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.
Beyrer also noted that infections in the United States, Britain and Germany seemed to be increasing at a significantly faster rate than they were in South Africa.
“This is an incredibly infectious virus and it is moving right along,” Beyrer said. He added that the United States has numerous tools — including ready access to vaccines and booster shots, the new antiviral medicines, testing and masking — that could help curb its effects.
But referring to those who have refused to follow public health guidelines, Beyrer said, “We have a lot of resistance so that makes us vulnerable to infection.”