The Omicron variant doesn't seem to be making people sick as much as Delta did.
The pattern seemed to hold as the variant spread to Europe and North America, and South African doctors first noticed it in November.
Most Omicron cases in the US have only a few symptoms, including cough, fatigue, and congestion, according to the Centers for Disease Control and Prevention. The top Omicron symptoms reported to the ZOE COVID-19 symptom tracker are headaches, fatigue, sore throat, and sneezing.
Omicron's rapid spread doesn't seem to be driving up the number of hospitalizations as much as previous strains. A report from Imperial College London found that people with Omicron had a lower risk of being hospitalized than those with Delta.
Scientists are still unsure if Omicron is less virulent or if vaccines and prior infections are preventing more people from getting sick.
The director of the Center for Evolutionary Biology and Medicine at the University of Pittsburgh told Insider that the reason Omicron is not as severe is because it has evolved to a less virulent state.
He said that he thought that was nonsense. I think it's because it's infecting people that have already seen a coronaviruses before.
The researchers at Imperial College London said last week that Omicron had limited changes in severity compared to Delta. They found that Omicron was less likely to produce severe disease than Delta after controlling for factors like age, underlying health conditions, and vaccination status.
Unvaccinated people may face the same risk of disease from Omicron as they did from other variations.
The study found that the risk of severe outcomes didn't change much for people who had Omicron or another variant of COVID-19. The study didn't control for previous infections or vaccination status and hasn't been peer reviewed yet.
"I'm still of the opinion that our immunity is working well," Jetelina told Insider. There is still no evidence that Omicron is causing less severe disease.
T cells from vaccines can help ward off disease.
A rapid test sample is being processed.
Brittany Murray is a reporter for the Long Beach Press-Telegram.
People who have received a booster shot are proving to be a powerful tool against Omicron.
Discovery Health, South Africa's largest private health insurance administrator, found that two doses of Pfizer's vaccine were 70% effective at preventing Omicron hospitalizations and 33% effective at preventing Omicron infections, based on a sample of around 78,000 Omicron tests.
A recent report from the UK Health Security Agency states that a booster dose may raise that protection to 70%-75%.
A small lab study published last week shows that a prior coronaviruses infection may confer some level of protection against Omicron.
The Omicron variant seems to be better at evading the antibodies than other ones. Antibodies can help ward off infections, but they're not the only form of protection. B cell and T cells can be activated by vaccines, which can stop an infection from getting worse.
T cells control a virus once you've been exposed, and that's what they do. Wendy Burgers, a researcher at the University of Cape Town, told Science on Monday that this is their time to shine.
Two doses of Pfizer's or Johnson & Johnson's vaccine produced a lower T cell response against Omicron than against the original strain, according to research by Burgers. In one Pfizer study, people who'd received two doses of Omicron had their neutralizing antibody levels plummet.
There is a chance that Omicron is less virulent.
People wait in line as city workers give out take- home COVID-19 tests.
Spencer Platt is a photographer.
Jetelina said there is still a chance that Omicron will be less dangerous than other strains.
The UK researchers found that Omicron may be less efficient at infecting certain cells relative to Delta or other coronaviruses, which may explain the mild disease observed among most Omicron patients. The University of Hong Kong found that Omicron had a harder time replicating in the lungs than the original coronaviruses.
"If it is less severe, our organs may not be as overtaken with Omicron than with Delta," Jetelina said.
Even if the variant is milder than the common cold, scientists warn that it's too early to dismiss Omicron cases as cold. Cases of Omicron are doubling every two to three days in the US, and hospitalizations are bound to rise as it spreads.
People still end up at the hospital even if Omicron is less severe. A small percentage can add up very quickly if a virus moves through 330 million people.
