Omicron Covid-19 Cases in U.S. Mostly Mild So Far

Report on 43 patients, most of whom were fully vaccinated, infection of the variant adds to the initial picture of the virus

The CDC said about 80% of people infected with Omicron were fully vaccinated, and a third had received a booster shot. Fourteen percent of the people had an infection of Covid-19 in the past. The CDC said patients usually have mild symptoms such as cough, fatigue, congestion or runny nose. About 60% of cases were in people between the ages of 18 and 39.

The report is an early piece of the picture that scientists are working to gather on Omicron’s infectivity and virulence relative to other forms.

First detected in South Africa last month, Omicron has a large number of mutations that have worried scientists and helped persuade the World Health Organization to label it “a type of concern.” Scientists say the mutation has the potential to increase transmittance and ward off infection- or vaccine-induced immunity.

“Many of the previously reported cases of infection of the Omicron type appear to be mild, although as with all types, a lag exists between infection and more serious outcomes,” the CDC said. The agency said mild cases could also be due to the fact that many patients were younger, people who were vaccinated or were previously infected.

The CDC said that even though most omicron infections are mild, a highly transmissible variant can trigger enough cases to affect health systems. The agency continues to recommend transmission-slowing strategies such as improving testing as well as vaccination, masking and ventilation, quarantining if exposed and isolating if infected.

For the past one month, Covid-19 cases have been increasing across the US. According to CDC data, as of December 4, more than 99.9% of cases indexed in the US were due to the delta variant.