A subvariant that scientists believe is even more contagious than the most common form of Omicron is spreading rapidly in parts of Asia and Europe and is now dominant in Denmark, where nearly all Covid restrictions were lifted last week.
For now, scientists are not expecting the subvariant, known as BA.2, to do significantly more damage than the version of Omicron that remains dominant in the rest of the world, BA.1. But they are concerned that BA.2 could extend the global Omicron surge, because it seems to be even more infectious than BA.1, which was already extremely contagious. The subvariant has been documented in at least 57 countries.
“This may mean higher peak infections in places that have yet to peak, and a slowdown in the downward trends in places that have already experienced peak Omicron,” Thomas Peacock, a virologist at Imperial College London, told The New York Times recently.
BA.2 doesn’t appear to cause more severe disease than BA.1, and vaccines are just as effective against it as they are against other forms of Omicron, Dr. Boris Pavlin, an epidemiologist at the World Health Organization, said at a news briefing last week.
One unanswered question is whether an infection from BA.1 builds immunity against infection from BA.2. Even if it does, scientists have cautioned that the protection from any previous coronavirus infection may wane over time, and may not apply as well to future versions of the virus.
BA.1 is still accounting for the vast majority of new Omicron cases around the world: 96.4 percent of them as of Jan. 31, according to the World Health Organization and the Global Initiative on Sharing All Influenza Data. But genetic sequencing indicates that BA.2 is quickly gaining ground, and it is expected to soon be dominant among new cases in India, Nepal, the Philippines, Qatar and other nations.
BA.2 already makes up about two-thirds of new cases in Denmark, the Statens Serum Institut, the country’s public health agency, recently reported, and is expected to account for nearly 100 percent of cases there by mid-February. Denmark has an extensive coronavirus surveillance system that scientists around the world watch for signals of where the pandemic could be headed.
Despite record hospitalizations and the uncertainty around BA.2, governments in Denmark and some other European nations are moving quickly to end pandemic protocols, betting that their highly vaccinated populations can endure the rest of the Omicron wave and whatever comes next.
On Monday, Portugal stopped requiring fully vaccinated travelers from abroad to show a negative test result, though unvaccinated visitors will still need to show one.
Norway has asked workers to return to their offices and has lifted limits on serving alcohol. The Netherlands is relaxing restrictions it adopted in December, which were among the strictest in the bloc. And Austria, which is making vaccinations mandatory for nearly all adults, has ended its lockdown for unvaccinated people.
Outside the European Union, Britain has scrapped most of the remaining pandemic restrictions in England. On Jan. 19, the country’s Health Security Agency designated BA.2 a “variant under investigation,” meaning it warrants more study but isn’t yet seen as a greater threat than BA.1. BA.2 still accounts for only a small share of new cases in England, but it is spreading rapidly there and is suspected of driving a surge in Northern Ireland.
In the United States, Trevor Bedford, a virologist at the Fred Hutchinson Cancer Research Center in Seattle, has estimated that about 8 percent of new cases are BA.2 and that the figure is climbing fast.
Sophie Downes, Carl Zimmer and Raphael Minder contributed reporting.