[Originally published: Dec. 2, 2021. Updated: Jan. 4, 2022]
Note: Information in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.
Last summer, the Delta variant swept through the world at a dizzying pace. Now Omicron is the newest worrisome virus variant, and the predominant strain in the United States. There is still a lot we don’t know, but experts are following emerging data closely to learn more.
Omicron: A spike in COVID-19 cases and potentially different symptoms
First, some background. Omicron (or B.1.1.529) is the latest coronavirus variant; it was first identified in Botswana and South Africa in November—although later reports showed earlier cases in the Netherlands. The first case in the U.S. was reported on Dec. 1 of last year in California. By late December, it became the predominant strain in the U.S. Both the WHO and the Centers for Disease Control and Prevention (CDC) have classified Omicron as a "variant of concern."
The new variant caused an alarming spike in COVID-19 cases in South Africa—cases went from 300 a day in mid-November to 3,000 a day at the end of that month. It’s also been identified in almost 100 other countries.
Early reports from South Africa indicate that most cases have been mild—and that symptoms for this variant may be different. “The reports show that patients in South Africa—many of whom were young—have had severe fatigue, but no loss of taste or smell,” says Lauren Ferrante, MD, a Yale Medicine pulmonologist.
Meanwhile, as people around the world welcomed a new year, Omicron surged more quickly than any previous variant in many areas. The new variant has driven a rising caseload in the U.S. that, at the end of 2021, far surpassed the record for new daily cases. However, numbers of hospitalizations and deaths were still far below what they were during previous virus peaks.
Is Omicron more transmissible—or deadlier—than previous variants?
From the beginning, two important questions about Omicron were top of mind for scientists, says Dr. Murray. The first is how transmissible the new variant is compared to Delta, previous variants like Alpha and Beta, and the original virus.
Based on early data from South Africa, Omicron was expected to outcompete Delta and will likely become the predominant variant strain in most places, as it is in the U.S. But questions still remain about what makes it more transmissible and how quickly it could rise to dominance, Grubaugh says.
The second question is whether Omicron is more likely than Delta or other variants to cause severe disease—if most infections continue to turn out to be mild, rapid transmission would be less of a threat, he says.
Do current vaccines protect against Omicron?
There is a third—and likely most important—question that has to do with how protective the existing vaccines will be against the new variant, says Dr. Murray.
There’s a key distinguishing factor for Omicron. Unlike Delta and other coronavirus variants, this one carries an abundance of mutations—about 50 in all, including 26 that are unique to the variant—and more than 30 on the spike protein, which is the viral protein that vaccines train the immune system to recognize and attack.
Grubaugh says some of Omicron’s enhanced transmissibility may come from its ability to evade some immune responses, especially in people who were previously infected, but not vaccinated. Scientists also want to know if these mutations indicate a possible reduction in the effectiveness of the COVID-19 vaccines and certain monoclonal antibody treatments, and if they are a sign that Omicron is a more contagious form of the virus.
“We don’t really know how the mutations work together. Not everything is additive,” Grubaugh says. But, again, it’s too early to speculate about the possibilities, he adds. “We really need to be careful and let the data speak for itself as it becomes available.”
Grubaugh says there is some preliminary laboratory data to show that antibodies generated from vaccines are less effective at neutralizing Omicron, although some of that loss can be restored with booster shots. In mid-December, an early real-world study from South Africa showed the Pfizer-BioNTech vaccine to be 33% effective at preventing infection and 70% effective at preventing hospitalization. But experts caution that South Africa has a different population than the U.S.—with more young people and high levels of prior infection—and more data will be needed to better understand the variant. That study was conducted by Discovery Health, the country’s largest private health insurance administrator, and it has not been published or peer-reviewed.
What you can do to protect yourself from Omicron
People need to understand that variants like Omicron are a natural part of the progression of the virus, Grubaugh says. “The fact that there is a new variant isn’t surprising,” he says. “Delta was never going to be the last variant—and Omicron is not going to be the last one. As long as there is a COVID-19 outbreak somewhere in the world, there is going to be something new that emerges.”
Both Grubaugh and Dr. Murray say the best way to prevent new variants is to get vaccinated, because if more people are vaccinated, it decreases the opportunity for the virus to spread and mutate. If you haven’t gotten your vaccine and booster shot yet, the CDC has endorsed choosing the Moderna and Pfizer-BioNTech vaccines.
In response to Omicron, the CDC is also urging everyone to get a COVID-19 booster shot when they are eligible. Recommendations for boosters and who is eligible to get one have been changing, and updated information is available on the CDC website.
Meanwhile, Omicron and Delta remain threats in the U.S., and experts continue to recommend protecting against those variants by maintaining infection prevention strategies such as wearing a mask in public indoor settings in areas of substantial or high community transmission, washing hands frequently, and physical distancing from other people.
Travelers to the U.S. should continue to follow CDC recommendations for traveling and related updates in response to Omicron. Doctors advise people who are planning trips to consider travel insurance.
“As the weather gets cold and people move indoors, we’ve started to see the virus spread again,” Dr. Murray says. “People can become fatigued with our warnings and precautions, but nobody wants to go backwards. We need to do everything we can to keep moving forward.”
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