BA.2, the newish and highly contagious Omicron subvariant, is now responsible for the majority of new Covid-19 cases sequenced around the world. That isn’t the news anyone necessarily wanted to hear at this point in the coronavirus pandemic, especially those who just had Covid during the Omicron surge.
Can you get BA.2 (sometimes called the “stealth variant”) if you recently recovered from the original Omicron variant or the Delta variant? And if so, how likely is it? Here’s what we know, and don’t, so far.
First, some background on BA.2
Though BA.2 only recently became the dominant Covid variant globally, it’s not new. Researchers first became aware of the subvariant in November and have been tracking it since then. It hasn’t always been easy. Initially, experts had a difficult time tracking BA.2 in PCR tests, which is how it earned its “stealth” nickname.
They know a lot more about it now. BA.2 is more infectious than the original Omicron variant – which itself was more infectious than previous strains, such as Delta. How much more contagious BA.2 is isn’t totally clear yet, but experts have guessed it’s at least 1.5 times more infectious than Omicron was.
The differences between BA.2 and the initial Omicron strain aren’t as big as those between Omicron and Delta. Early evidence also suggests they’re similar in terms of how sick they make people.
The World Health Organisation points to some very early reports from studies done in animals that concluded BA.2 may cause more severe illness than the original Omicron strain. But most of the evidence we have so far about cases in people point to BA.1 and BA.2 being pretty comparable in severity.
Yes, reinfection is possible
Reinfection with BA.2 among people who had the earlier Omicron strain has been clearly documented at this point, according to the WHO.
“Of course it’s possible,” Dr. Jennifer Lighter, a paediatric infectious disease specialist at NYU Langone Health in New York, told HuffPost regarding the possibility of reinfection. But she said there’s “clearly cross-protection” (meaning an effective immune response) between Delta and Omicron, as well as between BA.1 and BA.2. The exact timeline is imprecise, but experts tend to think you’ve got about 90 days of solid protection after infection.
There is also emerging population-level data that suggests widespread reinfection in a short period of time is pretty darn rare. A February study, which has not yet been subject to peer review and should be regarded accordingly, looked at a subset of samples from more than 1.8 million Covid infections from late November to February. They looked for people who had two positive samples, more than 20 days apart but less than 60 days apart, and found only 187 cases that appeared to be reinfections. Among those, 47 were cases in which a person got BA.2 after initially being infected with BA.1.
“There is the possibility of infection with BA.2 if you’ve had BA.1 although it is extremely rare,” said Dr. Erica Johnson, an internal medicine physician at Johns Hopkins Bayview Medical Center in Baltimore who chairs the Infectious Disease Board of the American Board of Internal Medicine. Johnson added that most of those reinfections were among the unvaccinated.
Which all seems to be pretty good news so far. As virologist Andrew Pekosz recently said in a podcast for Johns Hopkins Bloomberg School of Public Health: “The initial data suggests that if you’ve been infected with BA.1, you have pretty good immunity against BA.2.”
As always, vaccination and behaviour play crucial roles
Lighter said there are “different layers to your immune wall.” People who’ve only had two vaccine shots have a different level of immunity than those who’ve been boosted. Those who’ve been boosted, had a breakthrough infection and recovered probably have broader immunity than those who have never had Covid.
But according to experts like Lighter, the best way to make your immune wall “as robust as possible” is simple: Get vaccinated and boosted if you’re eligible.
“BA.2 will go through the unvaccinated,” she said. For parents worried about younger kids who are not eligible for vaccination, Lighter offered the reassuring news that severe illness from Covid – and from Omicron in particular ― tends to be rare in that age group.
As public health experts have dropped mask mandates and other Covid restrictions, they’ve been very clear about the importance of keeping abreast of Covid community levels where you live.
“I think the best thing you can do is be up to date on vaccinations,” Johnson said. Beyond that, monitor transmission within your community and make sure you’re following the most current guidance from health officials.
Otherwise, it’s probably safe to assume that you’re pretty well protected against BA.2 if you recently had Covid and recovered, and if you’re current on your vaccines, you’re definitely protected against severe illness. But as BA.2 circulates and other variants arise, which is likely, you probably shouldn’t behave as though you’re invincible, even if you recently had Covid-19.
Experts are still learning about Covid-19. The information in this story is what was known or available at the time of publication, but guidance could change as scientists discover more about the virus. To keep up to date with health advice and cases in your area, visit gov.uk/coronavirus and nhs.uk.