The new Omicron subtype BA.2 could prolong the current wave of COVID-19 infection, scientists say

• Scientists say the new Omicron coronavirus subtype BA.2 may extend the current wave of infections.
• Before BA.2 emerged, scientists were predicting a short, sharp Omicron wave.

Scientists tracking a more contagious Omicron subtype have warned that it could extend the current wave of COVID-19 infections. But it probably won't cause another massive surge, they added.

Previously, experts predicted a short, sharp Omicron wave in which cases would fall as quickly as they rose.

The more contagious BA.2 subtype has emerged just as countries started to remove restrictions and restart their economies. Scientists are scrambling to work out its potential effects.

On Monday, Eric Topol, the director of Scripps Research Translational Institute, said of the new BA.2 subtype, "Its increased transmissibility will prolong the Omicron wave in many places."

Topol cited data from countries in Europe and Asia where BA.2 has outcompeted BA.1 to become the dominant strain, as well as UK data released on Thursday, which estimated that the probability of household transmission was 30% higher for BA.2 than for BA.1, the original subtype.

Health officials in Denmark — where almost all new infections were BA.2 — said on Wednesday that the subtype appeared to be 1.5 times more infectious than BA.1, early data indicated.

Trevor Bedford, an affiliate associate professor in the Department of Genome Sciences at the University of Washington, agreed that BA.2 would cause "a substantially longer tail of circulation of Omicron" than would have existed with BA.1 alone.

But he added that it "won't drive the scale of epidemics we've experienced with Omicron in January."

Bedford said that in the US, about 60% of the population hadn't caught BA.1. "This leaves the potential for a more transmissible Omicron virus to spread further in this fraction of the population," he said. Reinfection of people who recovered from BA.1 may be possible, he added.

The average number of new reported COVID-19 cases in the US peaked at more than 800,000 a day on January 14, Oxford University's Our World in Data said. Now, new reported daily cases were below 500,000, the data showed.

Vaccines could help blunt another peak driven by BA.2.

UK data released on Thursday showed that two weeks after a booster, existing vaccines were 70% effective against symptomatic COVID-19 caused by BA.2. Meanwhile, three-shot protection against symptomatic BA.1 was 63%, the data showed.

A household study from Denmark, released on Sunday, found that increased transmissibility of BA.2 over BA.1 wasn't seen in households that had received two or three doses. The study hasn't yet been published or scrutinized by other experts in a peer review.

So far, it's unclear whether BA.2 is deadlier than BA.1. Early data from Denmark suggested that hospital admissions hadn't risen since the subtype took hold.