Can omicron variant overcome delta? Scientists try to find out

As scientists rush to understand the consequences of the omicron variant of Covid-19, one of the most important questions is whether this new version of the coronavirus can outperform the delta variant, which predominates globally.

The World Health Organization (WHO) on Friday (26) designated omicron as a “variant of concern”, just days after it was first reported in southern Africa. WHO said it is coordinating with many researchers around the world to better understand how the variant will impact the Covid-19 pandemic, with new findings expected in the next “days and weeks”.

Many questions remain, including whether omicron will avoid the protection of vaccines and whether it will cause more serious illnesses. But these features would be far less worrisome if the new variant remained relatively contained.

Several disease experts interviewed by Reuters said there are strong grounds for believing that omicron will make vaccines less effective. The omicron shares several key mutations with two earlier variants, beta and gamma, that made them less vulnerable to vaccines. In addition, the omicron has 26 unique mutations, many of them in regions targeted by vaccine antibodies.

Within months, however, the delta had spread much faster than any of its predecessors.

“So the question really is, what is the transmissibility of omicron relative to delta. That’s the main thing we need to know,” said John Moore, professor of microbiology and immunology at Weill Cornell Medical College in New York.

It is also likely to be one of the last to be answered, experts say. South African authorities raised the alarm about the omicron after identifying only dozens of cases of the variant.

Scientists will be watching closely whether cases caused by the omicron reported in public databases begin to outweigh those caused by the delta. That could take anywhere from three to six weeks, depending on how quickly the strain spreads, experts say.

Other information should arrive sooner. In two weeks, “we will have a better view of the severity of the disease,” said Dr. Peter Hotez, a vaccine expert and professor of molecular virology and microbiology at Baylor College of Medicine. “We’re hearing different reports — some say it’s a very mild disease and others report some severe cases in South African hospitals.”

Over a similar period of time, researchers said they expect early answers on whether the omicron can circumvent vaccine protection. Initial data will come from laboratory testing of blood samples from vaccinated people or laboratory animals, looking at antibodies in the samples after exposure to the new variant.

“Many labs are actively trying to make the omicron virus and test its sensitivity to antibiotics, and that will take a few weeks,” said Moore.

David Ho, a professor of microbiology and immunology at Columbia University in New York, believes the omicron will show a high degree of resistance, due to the location of its mutations in the virus spike protein.

“Vaccine antibodies target three regions of the coronavirus spike, and the omicron has mutations in these three regions,” said Ho. “We technical experts are much more concerned than public health experts, as far as we know from the structural analysis” of omicron.

Others comment that earlier variants, such as beta, also had mutations that made the vaccines less effective, but that these vaccines still helped prevent serious illness and death. Even as vaccine-induced neutralizing antibodies become less effective, other components of the immune system known as T and B cells should compensate, they said.

“Vaccination will likely continue to keep people out of the hospital,” said John Wherry, director of the Penn Institute of Immunology in Philadelphia.

The first real-world studies of the effectiveness of omicron vaccines in the community will likely take three to four weeks, as experts study the rates of so-called “invasive” infections in people who have already been inoculated, said Dr. Michael Osterholm, an expert in infectious diseases at the University of Minnesota.

Ho, from Columbia, said the fact that the omicron was already spreading in the presence of the delta, “which outperformed all other variants, is worrying.”

But others insist it is still an open question.

When it comes to specific mutations that could help omicron spread, “it doesn’t look very different from alpha or delta,” Hotez said.

Translated by Luiz Roberto M. Gonçalves