Trending Clinical Topic: Omicron

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Since its discovery in South Africa late last year, Omicron has dominated headlines and skyrocketed the number of COVID-19 cases in the United States and around the world. Its unique composition has been the subject of much research (see infographic below), and the highly transmissible variant of the coronavirus is this week’s hottest clinical topic.


Since last November, concerns about the mutational profile of Omicron have been evident. In the United States, the first case was reported on December 1. A month later, Omicron was estimated to have 95.4% of coronavirus strains in circulation. By early January, the variant had become the most dominant circulating form of the new 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 yet to be peer-reviewed suggests that unvaccinated people may be less prone to serious illness associated with Omicron. The study compared nearly 12,000 patients from the first three waves of COVID-19 with just over 5,000 from the Omicron wave. These 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 prior illness or whether Omicron is inherently less severe. This particular study concluded that about a quarter of the reduced risk of serious illness could be attributed to the characteristics of Omicron itself.

Despite the potential decrease in severity, the high transmissibility could lead to a significant number of deaths in the coming weeks. The Centers for Disease Control and Prevention (CDC) has predicted that up to 62,000 people could die from COVID-19 due to the latest outbreak in the United States. For the week ending Feb. 5, the CDC predicts 10,000 to 31,000 new deaths.

In terms of preventing serious consequences, a study in the UK found that a third booster dose is 88% effective in preventing hospitalization due to the Omicron variant. Regarding vaccination preventing transmission, a recent study in Israel found that a fourth booster dose does not prevent individuals from getting Omicron. In a clinical trial, 274 medical workers at Sheba Medical Center near Tel Aviv received a fourth dose of the vaccine in December – 154 received the Pfizer vaccine and 120 received the Moderna vaccine – after already receiving three Pfizer injections . Both groups received an antibody boost that was slightly increased. However, compared to a control group that did not receive the fourth dose, the additional booster did not provide increased protection against the spread of Omicron.

A vaccine specific to Omicron could 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 Stéphane Bancel said earlier this month. Moderna is also developing a vaccine that combines a COVID-19 booster dose with an experimental flu vaccine. As health systems continue to come under dramatic strain, the hope is that existing protections will help stem the tide of the latest wave. Until then, Omicron will likely remain the most dominant clinical topic.

Learn more about the variants of the coronavirus.

Jessica C. Bell