According to the U.S. Centers for Disease Control and Prevention, a study into a group of omicron infection cases in Nebraska has shown that the highly mutated variant causes milder or similar symptoms to those who have been vaccinated.

On Tuesday, the CDC released results from an epidemiological study into six omicron-related cases that were confirmed in a Nebraska household.

The symptoms started after a 48-year old man returned from Nigeria on November 23. He tested positive on Nov 26. He was also unvaccinated. The victim had had symptoms of the virus in 2020.

Before returning to the U.S., the man had an antigen test. The results were negative on November 21. He was still feeling symptomatic upon his return from the U.S. and had contact with five family members in Nebraska on Nov. 23 without wearing any mask.

His five children, including at least one child as young as eleven years of age.,The symptoms began between Nov. 24-26 and were confirmed by a subsequent test. One of the four had a history of symptomatic infections in 2020. The other two were fully vaccinated by Pfizer.

Unvaccinated, another member of the household had not tested positive for Covid previously. The person who was infected had mild symptoms of upper respiratory disease in November 2020, before any other household members.

The CDC stated that symptoms could take between 33-75 hours for household members, a median time of 3 days. It took this long to develop after exposure to the man who travelled. According to the CDC, the median time for Covid to incubate is five days. However, symptoms with the delta strain usually take about four days.

According to the CDC. Household members who had been reinfected suffered fewer symptoms than their November 2020 first infection. While two of the household members experienced fevers, no one reported losing their taste or smell.

Unvaccinated individuals who have never tested positive for omicron before had symptoms such as cough, joint pains, congestion, fever, chills, and headaches. After being positive for omicron in their household, no one needed hospitalization. After their initial infection in 2020, those reinfected didn’t require hospitalization.

California public health agencies reported the first known case of omicron on Dec. 1, in San Francisco. After a South African trip, the individual returned to California. The CDC found a person who had symptoms after returning from South Africa on November 15. This suggests that the variant may have entered the United States earlier.

Omicron was identified for the first time by South Africa in November and Botswana, December. According to the CDC the variant is now represented by 58% of the sequenced U.S. cases while delta accounts for approximately 41%.

Data from South Africa and Britain shows that people are not as sick with omicron than those who have the delta variant. U.K. Health Security Agency discovered that people who were infected by omicron had a 50-70% lower risk of needing hospitalization. South African researchers found that people who have been infected were 75% less likely to get severe illness.

The authors cautioned that it was not a good idea to look too closely at the initial data as vaccinations and immune responses could have affected the results.

According to another study by the U.K. Health Security Agency, a booster dose Pfizer/BioNTech vaccine provided 75% protection against symptoms of omicron. South African data suggest that two doses of Pfizer’s vaccine protect against serious illness but are less effective in preventing omicron infections.

New Covid cases in the United States are at near-pandemic levels. The nation reported an average of more than 237,000 daily new cases for the seven-day period ending Monday, up 66% over the past week, according to a CNBC analysis of data from Johns Hopkins University.

More than 70,000 people in the U.S. are currently hospitalized with Covid, up 3% over the past week, according to a seven-day average of data from the Health and Human Services Department as of Dec. 27.