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Omicron in the US: How the new COVID variant will compete with delta

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Twenty-five US states have reported cases of COVID-19 caused by the omicron variant, US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky reported Friday at the White House COVID-19 Response briefing. However, the delta variant remains the dominant variant in the US, responsible for over 99% of COVID-19 cases (which are up 37% from last week), hospitalizations (up 16%) and deaths (28% increase from previous week). 

With a virus as contagious as the coronavirus that causes COVID-19, any new variants that are even more transmissible than the original can cloud the path to recovery from a global pandemic. The delta variant, which scientists believe is at least twice as contagious as earlier strains, became the dominant US variant in July 2021 and quickly resulted in a spike of COVID-19 cases and hospitalizations. The vast majority of deaths and hospitalizations have been in people who are unvaccinated — according to CDC data, unvaccinated people were 14 times more likely to die from COVID-19 in September compared with fully vaccinated people. 

After scientists in South Africa identified omicron, the World Health Organization labeled the new variant a “variant of concern,” like delta, and researchers around the globe started the race to answer the questions: How effective are the vaccines and past COVID-19 infections against omicron? How does it compare to delta? Also in response, President Joe Biden issued a travel ban on eight countries in southern Africa where omicron is circulating. Omicron has been detected in many countries around the world, including the US. 

Right now, scientists think that omicron is likely to be at least as contagious as delta and that the level of contagiousness will strain health care systems if left unchecked. But they’re also confident vaccines will continue to be protective against severe disease, and the same public health measures we’ve been using to curb COVID-19 the last two years will also be effective against omicron. They’ve also strengthened the recommendation for booster doses, including for people as young as age 16. 

An early look at 43 US COVID-19 cases caused by the omicron variant, published in the CDC’s Morbidity and Mortality Weekly Report, offers a glimpse into how omicron will continue to unfold in the country. Of the 43 documented omicron cases in the report, symptoms were mostly mild, and only one person was hospitalized for two days. Eighty percent of people were fully vaccinated, and 14% of people had COVID-19 previously. No deaths have been reported. 

As scientists continue to collect information on omicron, here’s how it compares with delta so far. 

Is omicron worse than delta (or vice versa)?

It’s too early to tell for sure, but early signals of the severity of omicron are “encouraging,” Dr. Anthony Fauci, Biden’s chief medical adviser, told CNN — that is, there aren’t safety signals right now that show omicron leads to more severe COVID-19. In terms of how contagious the two variants are: “Clearly, in South Africa, omicron has a transmission advantage,” Fauci said, noting that we need to be “careful” about drawing too many conclusions before there’s more data, which might take a couple weeks. 

At the press briefing Tuesday, Fauci again stressed that data available now from South Africa does suggest that omicron has a “high degree of transmissibility,” but that scientists need more time to determine exactly how infectious it is compared with other variants, and whether it causes less or more severe infection than other variants. Data on COVID-19 hospitalizations in South Africa is encouraging, but also inconclusive because of the fact many people being affected by omicron are younger individuals, Fauci said.

Omicron has some similar mutations in its spike protein to the delta variant, according to the Republic of South Africa’s Department of Health, as well as the alpha, gamma and beta variants — all classified as variants of concern by the WHO. This means omicron will also be very transmissible, likely enabling the virus to more easily get around someone’s antibodies, lowering the vaccine’s efficacy against symptomatic disease (as in the delta variant’s case, scientists expect the vaccines to remain protective against severe COVID-19). Scientists from South Africa also believe omicron may lead to more cases of reinfection in people who’ve already had COVID-19. 

Omicron has more mutations on its spike protein than the delta variant does, but whether that means anything remains to be seen.

“What all those changes in the aggregate are going to do for the things that matter for this virus, we don’t really know yet,” Robert Garry, a virologist at Tulane University, told CNN.

What is a mutation or variant? 

The coronavirus enters our cells using its “corona,” or layer of protein spikes, then makes copies of itself in our bodies, where inevitably there are some errors or mutations, as explained by Yale Medicine. Sometimes those mutations in the virus are harmless, but other times — like in the case of the delta and omicron variants — they make it much easier for the virus to spread from person to person and infect more people. 

The more people who are unvaccinated or without immunity from COVID-19, the more opportunities there are for the coronavirus to spread and form concerning variants. 

“I think what you’re seeing is just the manifestation of what we’ve been talking about,” Fauci told NBC in November. “Why it is so important for people to get vaccinated, and for those who are fully vaccinated to get boosted.”

Apart from vaccine hesitancy, many people in countries outside the US don’t have access to a COVID-19 vaccine. According to Our World in Data, 7.1% of people in low-income countries have received a dose of coronavirus vaccine. 

“The emergence of the omicron variant should be a wake-up call to the world that vaccine inequality cannot be allowed to continue,” South Africa’s president, Cyril Ramaphosa, said in an address.

At the briefing Tuesday, White House COVID-19 Response Coordinator Jeff Zients announced that the US has shipped 300 million COVID-19 vaccine doses out for donation — a milestone, he said, in the White House pledge to donate 1.2 billion doses of COVID-19 vaccine to other countries.  

What are the symptoms of omicron vs. delta?

So far, people who have come down with COVID-19 from the omicron variant in the US have had mostly mild symptoms, which is “what we would expect,” Walensky said at a press briefing Friday, “in a group of fully vaccinated individuals.” In a Dec. 10 MMWR report, the details of 43 omicron cases are listed. In the report on their symptoms, most people (89%) reported a cough, 65% were fatigued and 59% of them were congested or had a runny nose. Only 8% of the 43 people reported losing their sense of smell or taste, which has affected many people with previous COVID-19 infections. 

Dr. Angelique Coetzee, a South African doctor who helped discover omicron, told the BBC that so far patients she’s seen with the omicron variant have “extremely mild cases” of COVID-19. Those symptoms included fatigue, headache and a scratchy throat, she said, not the telltale loss of smell or a cough associated with earlier COVID-19 infections. 

However, the delta variant may have slightly changed the way COVID-19 presents. Cough and loss of smell are also less common symptoms of COVID-19 caused by the delta variant compared with earlier variants, per the Baton Rouge General, a Mayo Clinic network. Cold symptoms like a headache and runny nose are now more common symptoms of COVID-19, according to the UK’s ZOE COVID Study

In general, it’s too early to make a claim that omicron has milder or more severe symptoms than delta. Although anecdotal evidence shows that confirmed cases caused by omicron have shown mild symptoms, most of those people have been younger adults, according to South Africa’s health department. Only 9% of the 43 people documented by the CDC were age 65 or older. Younger adults and children are generally less likely to experience severe COVID-19 than older adults. 

How do you test for omicron? 

A COVID-19 test won’t tell you which variant you have. In order for scientists to determine whether it’s omicron or another coronavirus variant, the CDC uses genomic sequencing. According to Walensky, the CDC director, the US is now testing 80,000 positive COVID-19 samples per week (about one in seven positive tests), up from 8,000 per week earlier this year.

Fortunately, the omicron variant is easily detected through PCR tests, according to Fauci, which can then be confirmed through labs that use genomic sequencing. 

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