The omicron variant of the coronavirus has been dominant in the United States since December, but the version of omicron that caused the main spike in infections over the winter now accounts for less than 2% of new cases.
A more transmissible subvariant, BA.2, accounts for about three-fifths of cases. And BA.2, in turn, spawned its own sub-lineage, BA.2.12.1, which grew from 7% of cases in early April to 36% by the end of the month.
Together, these subvariants lead to an increase in Covid cases in the United States – new daily cases have increased by 45%, on average, over the past two weeks, according to the NBC News tally.
So far, the main difference between the new versions of omicron and the one that has already exploded in the United States is the transmissibility. White House chief medical adviser Dr. Anthony Fauci estimated that BA.2 is 50% more transmissible than the original omicron line. BA.2.12.1’s recent gains suggest it has an added advantage over its predecessor.
But the cold symptoms experienced by those vaccinated and boosted following an omicron infection are mostly the same, regardless of the subvariant.
“Omicron symptoms have been pretty consistent. There are fewer people losing their sense of taste and smell. In many ways it’s a bad cold, lots of respiratory symptoms, stuffy nose , cough, body aches and fatigue,” said Dr. Dennis Cunningham, medical director of infection control and prevention at Henry Ford Health in Detroit.
Symptoms of the BA.2 subvariant
The Zoe COVID Symptom Study in the UK has enabled hundreds of thousands of people to self-report their symptoms via smartphone apps.
One of the apps’ co-founders, Tim Spector, a professor of genetic epidemiology at King’s College London, said that based on Zoe’s data, a runny nose remains the most common symptom of omicron , followed by fatigue, sore throat, sneezing, headache, cough and hoarse voice.
“The changes from BA.1 to BA.2 were quite subtle – maybe runny nose and fatigue [are] go up,” he said.
Spector said 84% of people in the UK who reported symptoms recently said they had a runny nose, up from around 73% in early January. Seventy-two percent said they had fatigue, compared to 68% in the first omicron wave.
But attributing these changes directly to a subvariant is difficult, Spector said, because there are many confounding factors.
What are the risks of reinfection?
BA.1 and BA.2 are about as genetically similar as delta was to alpha, the experts said. In general, the odds of contracting Covid after a previous infection increase over time, but Dr. Amesh Adalja, principal investigator at the Johns Hopkins Center for Health Security, said people who recovered from an omicron infection in the winter are likely to have protection against BA.2 for at least several months.
“If they share enough mutations to be classified as an omicron variant, there will likely be a lot of cross-protection. But over time, we know with all coronaviruses that reinfection becomes common as antibody levels drop. “, did he declare.
Your level of protection may also depend on how sick you have been before. Montefiori said immunity to an omicron infection can last from a month for asymptomatic people to a year for those who are seriously ill.
“When we look at immunity that has developed from an infection, the milder the infection, the less you benefit from it,” he said.
But Adalja said that even for those with mild cases, “it’s unlikely to see an erosion of protection against severe disease, which I think is really important.”
Differences between viral lineages and subvariants may also influence the effectiveness of monoclonal antibody treatments.
“We even know with BA.1 and BA.2, which are both omicron subtypes, that different monoclonal antibodies work for one but don’t work for the other,” Adalja said.
What about all these new omicron sublines?
BA.2 and BA.2.12.1 aren’t the only omicron subvariants that health officials are monitoring. In South Africa, two others – BA.4 and BA.5 – have caused a sharp increase in cases. These two sublineages have been detected in at least 13 US states as well as Washington DC.
A small pre-print study by South African scientists, published online last month, suggested that people previously infected with the original omicron variant might not have much protection against BA.4 and BA.5.
“It’s like the virus is trying to find a way to break through the immunity that has built up in the population,” said David Montefiori, a professor at the Human Vaccine Institute at Duke University Medical Center.
Still, he said, the public shouldn’t worry too much about the emergence of each omicron sub-variant.
“At some point, you just can’t get nervous every time there’s a new variation, because there’s always going to be a new variation,” Montefiori said. “We went through several waves of variants that really mattered a lot, but we could come out of it because there is so much immunity built up in the population.
What about those who haven’t caught the Covid yet?
Vaccinations, masks, testing and social distancing can help control the spread of dominant omicron strains, experts have said.
Although scientists are still studying how vaccine protection fare against new subvariants, Adalja said, young, healthy people probably won’t need a fourth vaccine.
“With these first-generation mRNA vaccines, it’s hard to get anything other than protection against serious disease over a longer period of time because of the evolution of variants like omicron,” he said. declared.
Rapid tests, on the other hand, readily pick up BA.2, although they are generally less sensitive to omicron than they were to delta. Data from the Zoe COVID Symptom Study showed that home tests were 85% sensitive to delta and 80% sensitive to omicron.
“These home tests still work well enough to get 80% accuracy,” Spector said. “They don’t give false positives either.”