People who have recovered from infection with the new Omicron coronavirus variant may be able to ward off later infections of the Delta variant, a new lab study by South African scientists shows.
If further experiments confirm these findings, they could point to a less bleak future for the pandemic. In the short term, Omicron is expected to trigger a wave of cases that will put tremendous strain on economies and healthcare systems around the world. But in the longer term, the new research suggests that an Omicron-dominated world may experience fewer hospitalizations and deaths than a world where Delta continues to rampage.
“Omicron will likely push Delta out,” said Alex Sigal, a virologist at the Africa Health Research Institute in Durban, South Africa, who led the new study. “Maybe it’s a good thing to push Delta out, and we’re looking at something that we can live with more easily and that will bother us less than the previous variants.”
He posted the new research on the institute’s website on Monday. It has not yet been published in a scientific journal.
Independent scientists said the results of the South African experiment, while preliminary, were solid. Carl Pearson, an epidemiologist at the London School of Hygiene & Tropical Medicine, said the findings were consistent with what is now happening in England.
“Omicron is arriving and growing rapidly, and the Delta trend is turning downward,” he said.
And Nathan Grubaugh, an epidemiologist at the Yale School of Public Health, said he observed the same pattern in Connecticut. “We see Omicron rising exponentially while Delta cases are falling,” he said. “This suggests to me that Omicron outperforms Delta for sensitive individuals, making them less susceptible to Delta in the aftermath, dispelling Delta cases.”
When people became infected with the coronavirus two years ago, they made antibodies and immune cells that could offer protection against it. As a result, it was very rare for a person to be re-infected in the following months.
But from the end of 2020, new coronavirus variants appeared. Some of them, like Alpha, had mutations that allowed them to spread quickly. Others, like Beta, had adaptations that allowed them to evade antibodies — whether they were produced during a previous infection or in response to a Covid-19 vaccine.
Delta, which came to prominence in the summer of 2021, had mutations that gave it both a superior ability to propagate and a mediocre ability to evade antibodies. Vaccines still remained effective against Delta, but not as much as before in the pandemic.
When Omicron appeared in November, it spread faster than even Delta. Researchers suspected the speed had two sources. Somehow it was able to transmit quickly – perhaps by replicating in large numbers or by spreading more easily from one person to another. Omicron was also able to infect vaccinated people and those who had become ill with previous variants.
In an earlier study this month, Dr. Sigal, as well as a number of other research groups, explored Omicron’s ability to evade antibodies from vaccines and previous variants. To do this, they analyzed blood from people who had been vaccinated or recovered from Covid, and mixed it with different variants.
Time and again, antibodies that were very potent against Delta and other variants did a poor job against Omicron. This helped explain why so many vaccinated and previously infected people get attacks of Omicron, albeit milder than Delta infections.
In their new study, Dr. Sigal and his colleagues performed the same experiment, but this time on people who had recovered from Omicron infections. While South Africa has just experienced a massive spike in Omicron cases, Dr. Sigal and his colleagues have only been able to study 13 patients so far.
“This was very difficult because of the holiday season,” he said. “Nobody really wants to stick around and be part of a study.”
Seven of the patients were vaccinated and six were not. The scientists have not identified which volunteers were previously infected with other variants of Covid. But since the vast majority of South Africans had Covid before Omicron, it is likely that most of the volunteers were not first infected with Omicron.
Unsurprisingly, the researchers found that the patients’ blood contained high levels of antibodies that are potent against Omicron. But those antibodies also turned out to be effective against Delta.
This was especially surprising because the team’s study earlier this month found that the reverse was not true: Antibodies produced after Delta infection offered little protection against Omicron.
As Omicron hurtles across country after country, Dr. Sigal that it would give people immunity not only for themselves, but also for Delta. That would mean that people who become infected with Delta have fewer chances of passing the virus on to others. At the same time, Omicron will easily infect people who have recovered from Delta. That competitive advantage could spell the demise of Delta.
That, of course, is a lot of speculation about the future health of billions of people based on just 13 volunteers. In addition, Dr. Sigal doesn’t say exactly what the advantage is that Omicron offers against Delta. It is possible that the antibodies it produces also act more broadly against other variants.
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Alternatively, it is also possible that the Omicron infections simply induced the existing immunity in volunteers, either through vaccinations or previous infections. If that’s true, it remains to be seen what will happen to unvaccinated people who become infected with Omicron for the first time — a fate that millions of Americans will experience in the coming weeks.
Even if Omicron wipes out Delta, that doesn’t mean Omicron will reign supreme for generations. Once people gain immunity to Omicron, natural selection may favor mutations that produce a new variant that can escape that immunity.
Depending on the specifics of the coronavirus, said Dr. Pearson that he could foresee three different futures.
In one, Covid mimics the flu, with one seasonal variant displacing the previous year after year.
In a second, Covid mimics dengue fever, with several variants coexisting that evade different antibodies, causing people to get sick with one of them every few years.
The third possibility is the most desirable: one variant wins and becomes an easily preventable pathogen. But dr. Pearson considers that the least likely scenario.
“I bet we can rule out that it tends to be a place where it gets stuck in a single variety that immunizes for a long time and becomes a childhood infection like measles,” he said. “But that is also possible.”