Early signs indicate that the omicron variant, flying across the globe at breakneck pace, might produce less severe illness than previous variants of concern.
Scientists are unsure if the variant itself is less lethal or whether population immunity from previous infections and vaccination has meant that it is less able to wreak havoc. Either way, though, infectious disease experts are taking some solace in the evidence that omicron is not the worst-case scenario.
Early data out of South Africa, where omicron was first identified, looks relatively promising. A study conducted by Discovery Health, a South Africa insurance provider, projected a steeper trajectory of new cases relative to previous waves, but a flatter trajectory of new hospitalizations. From the time of its discovery in late November through roughly three subsequent weeks, people infected with COVID-19 were 29% less likely to be hospitalized than in the initial pandemic wave beginning in March 2020.
Similarly, a study funded by the South African Medical Research Council found that omicron infections were associated with 70% lower odds of severe disease than delta infections.
It's possible that those welcome results are attributable to the relatively high rate of population immunity. Most South Africans have been exposed to the virus. The country has endured three robust waves of COVID-19.
"This reduced severity may be in part a result of high levels of population immunity (due to natural infection and/or vaccination)," the study concluded.
In other words, it may not be that the omicron variant is inherently less lethal. Rather, it may be that population immunity makes it effectively less lethal — that it is better able to infect people who've been vaccinated or had COVID-19 without necessarily making them severely ill.
If indeed population immunity in South Africa has protected the country from the worst effects of an omicron wave, that provides the United States with hope, as most people have been infected, vaccinated, or both. The U.S. benefits from a higher level of vaccination coverage than South Africa — 65% of Americans age 5 and up are vaccinated, compared with roughly 24% of the South African population, according to Reuters.
"This is going to be less severe, either because of immunity or intrinsic severity or both," said Trevor Bedford, a researcher at the Fred Hutchinson Cancer Research Center, told New York magazine.
"Even if we’re not completely at endemicity, we’re pretty close. And so this may be, effectively, what endemicity looks like, and we can see how bad that feels," Bedford said.
Still, population-level protection won't help those who are unvaccinated and don't have natural immunity and thus face higher odds of hospitalization and death, according to Dr. David Celentano, an epidemiologist and health risk behavior expert at Johns Hopkins Bloomberg School of Public Health.
"So many people in South Africa have already been infected with another variant — hence, less severity," Celentano said, adding that immune protection from exposure to the virus is not as strong as protection from receiving two doses of the Pfizer or Moderna vaccine plus a third booster dose.
Enough people remain unprotected and omicron spreads fast enough to present a major risk. “There’s going to be massive disruption … going across all of society,” said Dr. Ilya Finkelstein, a molecular biologist at the University of Texas, Austin. “Intrinsic severity is not going to be significantly lower in order of magnitude, but if the case numbers spike, even if it's slightly lower [in lethality], intrinsically, it doesn't matter.”
Even a less severe strain could cause hospitals to buckle. A majority of hospitalizations are among the unvaccinated.
Hospitalizations due to the omicron variant in the United Kingdom, which was hit by omicron early, have reached 129, with 14 confirmed deaths. Just four days ago, the U.K. Health Security Agency had reported 65 cases and a single death.
In the U.S., cases and hospitalizations have been on the rise since mid-November. The daily average number of new COVID-19 cases has reached roughly 133,000, up 21% from two weeks ago. Hospitalizations, meanwhile, have climbed 16% in the past two weeks, reaching a seven-day average of nearly 70,000.
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Scientists will get a better idea in the coming weeks of how omicron attacks the immune system as additional hospitalization data come in. Doctors in South Africa have reported that people vaccinated with Pfizer’s mRNA vaccine “had 70% protection against hospital admission” in the weeks toward the end of November and the start of December.