What the omicron subvariant BA.2 might mean for Minnesota

Experts have been saying that the omicron wave in December and January wouldn’t be the last of COVID-19; pandemics just don’t end with one, gigantic final wave. Now, a new subvariant of omicron looks like it might cause a new spike in cases.

That subvariant is called BA.2, and has been nicknamed “stealth omicron.” It was first identified late last year and has spread quickly around the world. Early data suggest BA.2 spreads between people even more easily than even omicron, though it does not seem to cause more severe disease.

Data from Minnesota show BA.2’s rise in the state. While case counts remain low, the Minnesota Department of Health’s surveillance system shows that the share of cases caused by BA.2 nearly tripled in a week, from 10.4 percent the first week of March to 29.5 percent the week of March 6 to March 11.

Those data are preliminary and do have a lag, so they don’t represent an up-to-the-minute picture of COVID-19 cases in Minnesota. Still, they’re a pretty strong indicator that BA.2’s reach is widening.

Still, while it’s clear that BA.2 is in Minnesota, how big of a wave it will cause — both in terms of cases, but also in terms of hospitalizations and deaths — isn’t yet clear.

‘Bro-micron’

BA.2 is considered a subvariant and not a variant of COVID-19 because it’s descended from omicron. Compared to regular omicron, though, its genetic sequence includes differences in some of the amino acids in its spike protein and other proteins, the World Health Organization says.

“It’s very much like omicron. I’ve heard people call it bro-micron,” said Dr. Rebecca Wurtz, associate professor, Division of Health Policy and Management at the University of Minnesota’s School of Public Health.

BA.2 behaves a lot like omicron — its symptoms are similar. And like omicron, BA.2 seems to be well-controlled by COVID-19 vaccines, particularly in people who have gotten a booster shot, Wurtz said.

BA.2 is more contagious, though.

“In a room full of absolutely unvaccinated people, if there’s one person with BA.2 in the room, more people are likely to catch it than if it were in the original omicron variant,’ Wurtz said. “Other than that, it’s not more serious, but in an unvaccinated person, it still is, or can be, a serious illness and can cause death.”

That BA.2 is circulating in Minnesota is not unexpected. BA.2 has been spreading quickly in other parts of the world, including the U.K., and some parts of the U.S. The CDC’s variant tracker estimates more than half of cases on parts of the East Coast are BA.2.

What BA.2 waves look like around the world

In China, BA.2 is contributing to extremely high COVID-19 case counts, hospitalizations and deaths. Because of strict COVID-19 mitigation measures, there is little natural immunity to COVID-19 in the population, and lockdown strategies implemented to stop transmission don’t work as well against highly transmissible BA.2.

Further, while China’s overall vaccination rate is high, the country’s COVID-19 vaccines, which uses an inactivated virus (much like what is used for flu vaccines) to stimulate the immune system, seem to be less effective than the mRNA vaccines common in the U.S. Vaccination rates are also low among the elderly.

Cases are rising again with BA.2 transmission too in parts of Europe, where vaccination rates are relatively high and mitigation measures have looked more like the U.S.

It’s early, but BA.2 does not yet seem to be causing a spike in COVID-19 cases on parts of the East Coast of the U.S. where it makes up a larger proportion of cases than it does here.

BA.2 in Minnesota

So what lies ahead for Minnesota?

Garry Bowman, a spokesperson for MDH, said that some assessments predict an increase in cases in the coming weeks in Minnesota due to BA.2. That increase isn’t here yet, as cases remain stable.

“It is nearly impossible to compare countries or even states within the U.S. due to ever changing policies around social gatherings, masking, and other precautions that can limit the spread of disease,” Bowman said.

Dr. Jill Foster, pediatric infectious diseases physician at the University of Minnesota, said she doesn’t see a repeat of the omicron wave, when hospitals were overwhelmed and many health care workers were out sick, creating staffing emergencies, as being likely with BA.2.

“I don’t think it’s going to hit that badly this time. I think that lots of people will probably get it but aren’t going to get it so severely because they have some pre-existing immunity,” she said.

It is a good time for Minnesotans to get vaccinated or boosted if eligible. Immunity from natural infection is thought to last around 90 days, which means many of the people who got omicron in December and January may have waning immunity now, Wurtz said.

It is not yet clear how protective previous omicron infectious is against reinfection with BA.2. Still, more people have booster shots now than did during the omicron spike. Plus, the weather is warming up and people will be spending less time indoors where transmission happens more readily.

So how should Minnesotans be thinking about BA.2?

Again, people should get vaccinated and get a booster shot if they haven’t yet. Vaccines, particularly with the booster, are holding up well against omicron and they’re the best defense against severe illness and death.

It’s also important to protect the most vulnerable people. That means taking tests if you’re going to be around vulnerable people, Foster said.

Still, if you are vaccinated and aren’t in a vulnerable group, Foster said it’s probably OK to loosen up for now while cases are low.

“Take this as an opportunity to go out and do the things you haven’t been doing for two years. Go to a restaurant, but then also be smart,” she said; it doesn’t have to be all or nothing, either: Foster said she recently ate at a crowded restaurant and wore her mask in the grocery store on the same day.

“The odds are, it is coming back and you’re going to have to start tightening back up again,” she said.