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People reinfected with omicron variant had fewer symptoms, small CDC study finds

The report, which looked at six people, also suggests the incubation period for the new variant may be shorter.
Image: Health workers administer Covid-19 in Farragut Square in Washington on Dec. 23, 2021.
Health workers administer Covid-19 vaccinations in Farragut Square in Washington on Thursday.Evelyn Hockstein / Reuters

People who had Covid-19 and are later reinfected with the omicron variant may experience fewer symptoms than they did during their initial bout with the virus, a small study from the Centers for Disease Control and Prevention suggests.

The study, published Tuesday in the CDC's Morbidity and Mortality Weekly Report, looked at six people in a single household with confirmed cases of the highly contagious variant, five of whom were previously infected with other strains of the virus. One reinfected person was fully vaccinated, but had not received a booster.

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The CDC study comes one week after Scottish researchers reported preliminary findings suggesting the rates of reinfection with the omicron variant are much higher compared to delta.

The CDC report focused on six individuals in Nebraska. One of the people, a 48-year-old man who was unvaccinated but previously infected, had traveled to Nigeria in November.

Five others in the household subsequently got sick, and all cases were confirmed to be the omicron variant.

Five reinfected people told investigators their symptoms with omicron were similar or milder than they were during their first infection with the coronavirus, according to the report.

None of the five reinfected people reported a loss of taste or smell while infected with omicron, even though four of them did report those symptoms during their first infection. Two people reinfected with omicron reported fever, compared to four reports of fever from the initial infections.

The one person without a previously documented infection, who was unvaccinated, experienced cough, joint pain, congestion, fever and chills, according to the report.

None of the six people required hospitalization for either bout with Covid-19. Last week, reports out of the United Kingdom found that people who were infected with the omicron variant in November and December were about two-thirds less likely to be hospitalized, compared with the delta variant.

The CDC report also found that the incubation period for the omicron variant — that is, the amount of time from when a person is infected to when symptoms begin — appears to be shorter than previous strains: approximately three days versus four days or more.

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Overall, the findings suggest "a shorter incubation period and a clinical syndrome similar to or milder than that associated with previously described variants in persons who have been vaccinated or previously infected," the researchers wrote.

The CDC study adds to growing evidence that the new variant may be less likely to cause severe disease, particularly in those who have already been infected.

The new variant continues to spread rapidly in the United States, making up about 58 percent of all new Covid cases for the week ending Dec. 25, according to agency data.

Federal health officials, including Dr. Anthony Fauci, the White House's chief medical adviser, have warned the new strain could lead to a sharp rise in new infections as the holiday season ends and the nation enters the new year.

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