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Since its discovery in South Africa late last year, Omicron has dominated headlines and exploded COVID-19 case counts in the United States and worldwide. Its unique composition has been the subject of much investigation (see Infographic below), and the highly transmissible coronavirus variant is this week’s top trending clinical topic.
Since last November, concerns about Omicron’s mutational profile were evident. In the United States, the first case was reported on December 1. A month later, Omicron was estimated to be 95.4% of the coronavirus strains circulating. By early January, the variant had become the most dominant circulating form of the novel coronavirus worldwide, according to the World Health Organization (WHO).
The WHO and others have suggested that the highly infectious variant may cause less severe disease than the Delta strain. This information is still under investigation. A South African study that has not yet been peer-reviewed suggests that unvaccinated individuals may be less prone to severe illness associated with Omicron. The study compared nearly 12,000 patients from the first three COVID-19 waves with just over 5000 from the Omicron wave. Those data show less severe disease and proportionally fewer hospital admissions and deaths. However, researchers are investigating whether this is due to higher population immunity associated with vaccination or past illness or whether Omicron is intrinsically less severe. This particular study concluded that approximately a quarter of the reduced risk for severe disease could be attributed to characteristics of Omicron itself.
Despite the potential decreased severity, the high transmissibility may result in a significant number of deaths in the coming weeks. The Centers for Disease Control and Prevention (CDC) predicted that as many as 62,000 individuals may die of COVID-19 due to the latest surge in the United States. For the week ending February 5, the CDC projects 10,000-31,000 new deaths.
In terms of preventing severe outcomes, a study from the United Kingdom found that a third booster dose is 88% effective in preventing hospitalization due to the Omicron variant. When it comes to vaccination preventing transmission, a recent study from Israel found that a fourth booster dose does not prevent individuals from contracting Omicron. In a clinical trial, 274 medical workers at Sheba Medical Center near Tel Aviv received a fourth vaccine dose in December — 154 got the Pfizer vaccine and 120 got the Moderna vaccine — after previously getting three Pfizer shots. Both groups received a boost in antibodies that was modestly increased. However, when compared with a control group who didn’t receive the fourth dose, the extra booster didn’t provide increased protection against the spread of Omicron.
An Omicron-specific vaccine may be developed sooner rather than later. Moderna’s vaccine candidate will enter clinical development over the next few weeks, and the company hopes to share data with regulators around March, CEO Stephane Bancel said earlier this month. Moderna is also developing a vaccine that combines a COVID-19 booster dose with an experimental flu shot. As healthcare systems continue to experience dramatic strains, the hope is that existing protections will help stem the tide of the latest surge. Until then, Omicron is likely to remain the most dominant clinical topic.
Learn more about coronavirus variants.