MONDAY, Feb. 7, 2022 (HealthDay News) -- Omicron COVID-19 patients are younger and have more breakthrough infections, a new study finds. But people infected with Omicron are also less likely to be hospitalized or need intensive respiratory support than those who'd gotten the earlier Alpha and Delta variants.
The researchers examined data on patients at Houston Methodist hospital, where by the start of 2022, Omicron was responsible for 98% of all new COVID-19 cases. By Jan. 5, Omicron had infected 4,468 of the hospital's patients, according to the study.
It took only three weeks from the time Houston Methodist identified its first patient with Omicron for the variant to account for the majority of new COVID-19 cases. It took about three months for the Delta variant to reach that milestone, the study authors noted in a hospital news release.
Viruses constantly change, resulting in variants that can be more or less severe.
The study found that the average age of Omicron patients was 44.3 years, compared with 48.3 for Delta patients and 50 for those with the first highly publicized COVID variant, dubbed Alpha.
The length of hospital stay was 3.2 days for Omicron patients, 5.4 days for Delta patients, and 5.1 days for Alpha patients. And 55% of breakthrough infections in vaccinated patients were caused by Omicron, compared with just over 5% for Alpha and 0.9% for Delta, the findings showed.
As of mid-January, the hospital had identified three patients with the so-called stealth Omicron (BA.2) variant. These were the first three cases discovered in Texas.
The study, published online Feb. 3 in The American Journal of Pathology, is the first peer-reviewed study of U.S. Omicron patients and their outcomes, according to corresponding author Dr. James Musser and colleagues. Musser is head of pathology and genomic medicine at Houston Methodist.
The hospital has sequenced nearly 80,000 SARS-CoV-2 genomes since the beginning of the pandemic â€” one of the largest, most comprehensive COVID sequencing studies in the United States.
There's more on the Omicron variant at the U.S. Centers for Disease Control and Prevention.
SOURCE: Houston Methodist, news release, Feb. 3, 2022