The omicron variant, the latest curveball in the pandemic, may lead to less severe cases of Covid-19 than earlier strains of the coronavirus, according to one of the largest real-world studies of omicron released so far.
That’s good news, but it could be overshadowed by other data showing that the variant is far more contagious than any version of the virus to date — and that it can evade some immune protection from vaccines and prior infection.
Taken together, these traits make for a counterintuitive situation: Omicron poses a lower risk to most individuals, at least for those who are vaccinated, but the threat to the overall population is high. The question now is whether omicron will infect so many people that it overwhelms the health care system and drives up hospitalizations and deaths — in spite of the smaller percentage of people who come down with severe disease.
The answer is partly in our hands. The strategies that have contained Covid-19 throughout the pandemic still work against omicron, but governments, institutions, and individuals have to be willing to use them.
What the science says about omicron so far
Viruses are always mutating, and RNA viruses like SARS-CoV-2, which causes Covid-19, are particularly mercurial. The more the virus multiplies and spreads, the greater the chances of a mutation. Most mutations have no effect or are harmful to the virus, but occasionally the virus undergoes a change (or group of changes) that makes the virus spread more readily, better evade the immune system, or cause more severe illness. Viruses with distinctive groupings of mutations are categorized as variants.
South Africa was one of the first places to detect the omicron variant of SARS-CoV-2 in November. South Africa’s largest private health insurer, Discovery Health, on Tuesday published a study looking at 211,000 Covid-19 test results, including 78,000 positive tests from omicron.
The study showed that hospitalization risk was 29 percent lower with omicron infections compared to infections in South Africa last summer, even after controlling for vaccination status.
So do vaccines shield against omicron? The study found the Pfizer/BioNTech mRNA vaccine mostly held strong, granting 70 percent protection against hospitalization and 33 percent protection against infection from omicron.
Vaccine protection against omicron infection isn’t as high as its protection against earlier variants, which may contribute to a higher rate of breakthrough infections. Pfizer reported last week that while the two-dose course of its vaccine showed diminished protection against omicron, a booster dose of its vaccine ramped it back up.
On Wednesday, Moderna released early data showing a similar pattern with its mRNA vaccine, with lower efficacy against omicron from the initial two doses but increased protection with a booster. Two other common Covid-19 vaccines — from Johnson & Johnson and from AstraZeneca and Oxford University — also generated a lower immune response to omicron compared to earlier variants.
Discovery Health cautioned that the findings only draw from three weeks of data, but researchers on the ground say it fits with what they’ve seen so far.
“One thing we found was that the patients were staying for a shorter time in hospital, and that was across all age groups recently, compared to over time,” said Harsha Somaroo, a public health medicine specialist at the University of the Witwatersrand. Somaroo is also an adviser to the health department of Gauteng, the South African province that has become the epicenter of the country’s omicron wave.
Omicron may still become a major threat to public health because what omicron lacks in severity, it makes up in transmission. “The rates of increase in the number of cases has been exponential. It’s the highest it’s ever been in the pandemic in Gauteng,” said Somaroo. “The increases we saw were around 300 percent increases week-on-week.”
Since its detection last month, omicron has already spread worldwide. “The reality is that omicron is probably in most countries, even if it hasn’t been detected yet,” World Health Organization chief Tedros Adhanom Ghebreyesus told reporters this week. Omicron is now in more than 30 US states, just as the country is facing another spike in Covid-19 cases.
Most US cases are still driven by the delta variant, but omicron could end up fueling a towering spike in hospitalizations and overwhelm the health system just as the winter respiratory infection season hits its peak.
What the best- and worst-case scenarios for omicron could look like
The higher transmission rate of omicron means that people who have so far avoided the disease are at higher risk of infection than before.
Omicron may be 25 to 50 percent more transmissible than the delta variant, according to some estimates. Delta is 50 percent more transmissible than the alpha variant, which itself is 50 percent more transmissible than the original version of SARS-CoV-2.
Omicron has also shown that it can cause breakthrough infections in vaccinated people and reinfections in people who had the virus before.
“One worry is: Even if it’s very mild in people who have some immunity, but we have very high reinfection rates, it’s going to get in all those nooks and crannies of people who have never been infected or vaccinated — and managed to avoid the virus this whole pandemic,” said Justin Lessler, a professor of epidemiology at the University of North Carolina School of Public Health.
It’s not certain that omicron will replace delta as the main variant in the US. But it will likely be a major driver of new Covid-19 infections well into the new year, according to Lessler. In the coming weeks, the answers to which path the US will take will inevitably emerge.
The higher infection rate of omicron could follow two main pathways. The US could see a rise in milder infections that don’t translate into a surge in hospitals — or there could be so many infections overall that omicron still drives more hospitalizations and deaths.
“Possible scenario number one is we’ll have more cases of less ... severity. That will mean fewer people will have to go to hospital,” Andrew Badley, an infectious disease researcher at the Mayo Clinic, told reporters last week.
“The second possible scenario is more cases, but because it will likely impact more of those who have not yet been vaccinated, the total number of cases will go up,” Badley added. “The fraction of cases that require hospitalizations might be lower, but because of the sheer number, we see lots more hospitalizations.”
What’s probably the best-case scenario — a rise in cases without a rise in hospitalization and death — depends a bit on luck. But it also depends on robust public health measures to slow the spread of the variant and ensure that hospitals have enough capacity to treat the patients who do fall ill.
Omicron outbreaks will be different depending on where they happen
While the recent findings from South Africa are important data points, countries like the US are starting with a different Covid-19 baseline, so some comparisons won’t hold.
South Africa is currently experiencing summer, while Americans are heading indoors as the cold sets in. About 72 percent of US adults are now vaccinated against Covid-19, compared to around 38 percent in South Africa.
However, South Africa also faced multiple waves of infection with different variants, so upward of 75 percent of the population may have been exposed to the virus at some point, providing a degree of protection, Somaroo said.
There’s also a lag between cases being identified, which happens quickly, and hospitalizations and deaths that come later. A month of omicron in South Africa doesn’t provide a complete picture of the dangers of the variant.
The US has also struggled with big regional variations in vaccination rates, adherence to public health precautions, and overall Covid-19 cases across the country. “The US is very heterogeneous right now in terms of its experience of the pandemic,” Lessler said. The impacts of omicron will be very different where high numbers of people are vaccinated with booster shots, compared to a place where vaccination rates are low.
The Covid-19 playbook still works against omicron, but fewer people are sticking to it
Getting vaccinated against Covid-19 and getting a booster dose six months later remain the most effective things individuals can do to protect themselves against omicron. And many of the standard public health precautions remain effective — handwashing, wearing a face mask, social distancing, testing, contact tracing, and isolating in case of infection.
For the people who get infected, there are now more treatment options, and soon antiviral pills may be widely available. That could keep even more people out of hospitals.
But almost two years into the Covid-19 pandemic, public patience is wearing thin, and the will to pursue many tactics is fading. The news that omicron may be less severe than other variants could worsen a sense of complacency. It’s also a tough messaging challenge for public health officials.
“How do we confront this where many of us will be at relatively low risk if we end up getting infected — but the secondary impacts of an out-of-control wave that fills up the hospitals with cases ... could be quite dire?” asked Lessler.
What we know about omicron is still preliminary. Our understanding of its spread and severity could still change, so people should remain ready to adapt. “There’s a ton of uncertainty,” Lessler said. “Even the best-supported suppositions are far from sure.”