Federal health officials reported on January 25 that the Omicron COVID variant caused less severe illness in hospitalized patients than earlier virus lineages, even though its explosive transmissibility has caused far more infections and led to more than 2,200 deaths a day on average, one of the highest tolls since early last year. Researchers at the Centers for Disease Control and Prevention said that people hospitalized with the omicron variant had shorter stays and less frequent admission to intensive care compared with those hospitalized with other coronavirus variants.
Despite record infections and hospitalizations caused by Omicron, the percentage of hospitalized patients with severe illness is lower compared with those in earlier pandemic waves. That lower disease severity is partly the result of immune protection from higher vaccination coverage among those 5 and older, booster use, and previous infection, as well as the potential lower virulence of the virus itself, according to the report. Other studies have suggested that the variant is less able to penetrate deep into the lungs. That pattern notwithstanding, the virus spreads from person to person with frightening speed, resulting in significant numbers of hospitalizations and deaths. On January 25, the seven-day average of daily deaths in the United States was 2,230, the highest since late February 2021.
“People with underlying conditions, people with advanced age, people who are unvaccinated, can have a severe form of covid-19, following infection from omicron,” World Health Organization epidemiologist Maria Van Kerkhove said this week. “People are still being hospitalized with this variant, as well as dying.” The strain on health systems stemming from the large numbers of infections underscores the importance of hospital surge capacity and the ability to adequately staff healthcare systems, the report said.
The CDC report’s findings are consistent with recent studies from health systems in California and Texas, as well as from South Africa, England, and Scotland. One of the studies, a preliminary report by Kaiser Permanente that has not yet been peer-reviewed, looked at nearly 70,000 covid-19 cases in Southern California from November 30 to January 1. It found that rates of hospitalization, admission to intensive care units, use of mechanical ventilation, and death were all substantially lower in patients infected with omicron compared with the delta variant. Hospital stays were also shorter.
“What sets this report apart is that it focuses on the overall impact of the three waves on the health system, more than on ‘severity,’” Andrew T. Pavia, a professor of pediatrics and infectious diseases at the University of Utah, said in an email on January 25. He did not take part in the study. “The omicron wave has been bad news with the largest societal and health care impact, but for infected individuals, particularly those who are vaccinated, the decreased overall severity is good news,” Pavia said.
The data reinforces the importance of being up to date with vaccinations, including booster shots. Recent data from hospitals has shown that a booster shot is critical to preventing severe outcomes during the omicron surge. In a CDC study released last week, researchers showed that a third dose of either the Pfizer-BioNTech or Moderna shots reduces the chance of hospitalization by 90 percent compared with unvaccinated people, and reduces the chance of a trip to the emergency room or urgent-care center by 82 percent.