The ultra-transmissible coronavirus variant appears to be spreading at a much faster rate than the previously dominant delta variant, infecting both the unvaccinated and the vaccinated. On November 24, South Africa issued its initial alert about the newly identified omicron (B.1.1.529), and just two days later, on November 26, the World Health Organization (WHO) named it a “variant of concern.” The first case of omicron was reported in the United States on December 1, and by the week ending December 25, the variant accounted for a majority of cases in this country, according to the Centers for Disease Control and Prevention (CDC). Now, as COVID-19 case numbers spike, questions about whether to travel, gather, or head into the office are back on the table.
Why is omicron spreading so quickly?
When a virus infects a new host, whether an animal or person, it makes copies of itself. Some of these copies may have small genetic differences, called mutations. “As more people are infected, the range of mutations widens, though the vast majority of them go nowhere and don’t affect anything,” says Gabe Kelen, MD, director of emergency medicine at Johns Hopkins Medicine in Baltimore. But when a mutation occurs that makes a virus either more infectious or more harmful, that variant may start to predominate. That is because from a Darwinian perspective, that variant has an advantage that allows it to outcompete other versions of the virus, says Dr. Kelen. Of the approximately 50 mutations found in the omicron variant, more than 30 have been identified on the spike protein — the part that attaches to human cells. Scientists believe these mutations may help make omicron more transmissible than other variants such as delta, according to Yale Medicine.
How transmissible is omicron?
Omicron is highly transmissible. The variant is “exponentially increasing” in multiple countries, including the United States, according to the CDC. One reason for this fast spread is that the variant appears to evade immune protection conferred by prior COVID-19 infection or vaccination. Experts are still gathering information, but one report (not yet peer-reviewed) from the Imperial College London COVID-19 response team calculated that the risk of reinfection with omicron is 5.4 times greater than with delta. According to the authors, that implies that the protection against reinfection by omicron among those who have already had COVID-19 may be as low as 19 percent. People who are fully vaccinated are also experiencing breakthrough infections. One case report from the Norwegian Institute of Public Health (not a full study, but rather an investigation of an accident or individual illness) described a possible omicron super-spreading event at a company Christmas party in Oslo on November 27 where all attendees were reported to be fully vaccinated. A total of 110 of the 117 attendees were interviewed post-gathering, and 80 tested positive for COVID-19 in the two weeks following the party.
What are the symptoms of omicron?
Experts are still figuring out if the symptoms of the new variant are different than those of prior variants, says Panagis Galiatsatos, MD, assistant professor of medicine and pulmonary and critical care doctor at Johns Hopkins Medicine. “There are many of the same symptoms of earlier variants, but time will tell,” he says. Data about omicron infections gathered in South Africa by Discovery Health, the country’s largest private health insurance administrator, shows that symptoms include a sore throat (which appears to be a common early sign), nasal congestion, a dry cough, loose stool, and muscle pain — especially low-back pain.
Does omicron cause milder COVID-19 than delta?
Much of the early information about omicron is coming from South Africa. Health officials there reported preliminary data on December 17 indicating that only 1.7 percent of identified COVID-19 cases were admitted to the hospital in the second week of the variant’s takeover, compared with 19 percent in the second week of the delta wave. Data coming out from different parts of the world indicate that the risk for severe illness posed by omicron may be lower than the risk posed by delta. An early analysis from Imperial College London found that people infected with the variant are 40 percent less likely to be hospitalized for a night or more, compared with delta. That is reassuring, but “I’m concerned people will be lulled into a false sense of security by the reports that omicron isn’t as likely to cause severe disease,” says Dr. Galiatsatos. Although the variant may cause less severe disease, if it causes many more people to get sick, we could still be looking at high numbers of people ending up in the hospital — and that could strain our healthcare systems, he says. Plus there may be mitigating factors to consider when assessing whether findings from other countries apply to the United States. For instance, hospitalization rates in South Africa may be relatively low because the country has a young populace — the median age is 27. In the United States the median age is 38. In general, older people are at higher risk for more severe COVID-19. Initial findings from a joint study by South African and Russian scientists found that as with previous variants, the course of the disease is more severe in unvaccinated people with risk factors, especially older adults, according to a statement from the South African Department of Health.
Do COVID-19 vaccinations protect against omicron? What about boosters?
Researchers are studying how well vaccines protect against omicron and how long that protection lasts. A preprint Danish study posted to medRxiv on December 22 (not yet peer-reviewed) found that overall effectiveness against omicron was 55.2 percent with the Pfizer-BioNTech vaccine and 36.7 percent for Moderna. The study found that either a Pfizer or Moderna booster offered a “significant increase” in protection against omicron. Initial findings from Pfizer and Moderna are providing additional reassurance about the power of boosters to fight omicron. Moderna announced on Monday, December 20 that a booster dose of the COVID-19 vaccine increased the number of antibodies that fight the variant 37-fold. Pfizer-BioNTech said in a statement that its data indicates that its booster dose increases antibody response 25-fold. In a December 14 interview on NBC’s Today show, CDC Director Rochelle Walensky, MD, MPH, stated that vaccination and boosters help immunized people with breakthrough infections avoid severe COVID-19. “We’ve seen cases of omicron among those who are both vaccinated and boosted, and we believe these cases are milder or asymptomatic because of vaccine protection,” said Dr. Walensky. As for people immunized with the one-shot Johnson & Johnson vaccine, initial findings from lab experiments conducted in South Africa suggest that the J&J vaccine on its own produced almost no antibody protection against omicron, according to a Bloomberg report. But other research out of South Africa found that booster shots of the J&J vaccine are effective against the variant. The preprint study, posted to medRxiv onDecember 29, found that individuals who received two doses of the J&J vaccine reduced their risk of hospitalization from omicron by an estimated 85 percent compared to unvaccinated people. The CDC currently recommends that people who received the J&J vaccine get an mRNA (Pfizer or Moderna) vaccine as a booster.
What about kids and omicron?
There isn’t enough data to know if children are more or less at risk from omicron compared with adults, according to Children’s Health in Orange County (CHOC). Still, on December 27, New York State reported a “striking increase” in new hospital admissions for children. The vast majority were not vaccinated. In New York City, the number of children hospitalized grew from 22 to 109 from the week ending December 11 to the week ending December 23. The increases were concentrated in areas where omicron was first detected in the state, according to the statement. The CDC recommends vaccination for all children 5 and up, plus booster shots for those 12 and up.
Do at-home COVID-19 tests detect omicron?
For many of us, at-home tests have become a key component in keeping gatherings safe. Initial evaluations suggest that most antigen tests (the kind that can be performed at home without laboratory processing) do detect omicron but may have reduced sensitivity, according to the U.S. Food and Drug Administration (FDA). Lower sensitivity means that there is a greater chance that a rapid test will miss traces of the virus and give a false-negative result — telling you that you don’t have COVID-19 when you in fact are infected. If you have COVID-19 symptoms and a positive result from an at-home test, you don’t need to take another test to confirm that you have COVID-19, according to the University of Chicago. But if you have symptoms and test negative, you should not rule out COVID-19 but would ideally take a PCR test or repeat the antigen test the following day.
Do masks help protect you from omicron?
Most definitely, says Mohammad Sobhanie, MD, an infectious diseases physician at The Ohio State University Wexner Medical Center in Columbus. “There is a high level of COVID-19 throughout the country, and we know that wearing a mask and socially distancing are excellent strategies to reduce the chances of getting COVID-19,” he says. High-quality masks are especially important in light of the new variant. “We need to be promoting better high-quality masks everywhere, because right now a single-layer cloth mask just isn’t cutting it against omicron,” said former US Surgeon General Jerome Adams, MD, MPH, on CNN on December 24. The CDC recommends that everyone over the age of 2 — both vaccinated and unvaccinated — wear a mask in public indoor settings in places where COVID-19 transmission is high. Not sure about your area? Check the CDC COVID-19 County Check to find out local transmission levels and masking guidance.
