Can subvariant BA.2 reinfect people who have already caught the omicron? Understand

The omicron subvariant BA.1 infected many Brazilians until January. Now, BA.2 has caused concern for being more contagious. Can those who contracted the first version of the omicron strain reinfect themselves with BA.2?

After the omicron subvariant BA.1 was responsible for the Covid-19 outbreak that occurred between December and January and is still predominant in Brazil, BA.2 —which is already growing among infected people in the country– has caused concern among specialists for be more contagious than its predecessors.

BA.2 is already responsible for the increase in Covid-19 infections across Europe. Although it is more transmissible than the original omicron, data suggest that BA.2 does not cause a more severe form of the disease than the earlier subvariants of the omicron.

But who has already contracted the omicron can be reinfected with BA.2? When the omicron variant began to spread in late 2021, it sparked the biggest outbreak of the coronavirus pandemic. Omicron was thought to cause milder infections than earlier variants, even though it was more infectious.

Both people who had already recovered from Covid-19 and those who were vaccinated contracted the omicron – even those who received a booster dose of the anti-covid vaccine. The BA.2 subvariant may be more contagious than the original omicron, known as BA.1.

But the data so far are inconclusive, and scientists are divided. Some say we may be dealing with a completely new variant of the coronavirus.

Reinfections are possible but may be rare

Initial data from the UK show that some people are becoming infected with both the original variant of the omicron (BA.1) and its subvariant BA.2.

This appears to be supported by evidence from Vanderbilt University Medical Center in the US. Doctors told DW that they have seen cases of people being reinfected with the omicron, similar to data collected by doctors in the UK.

But Shira Doron, MD and associate professor at Tufts University School of Medicine in the US, did not report any reinfection with the omicron. Doron said the cases reported as reinfections could, in fact, be “false positives”.

“When I see someone who has been reinfected, I always invite them to retest. And I often see that the second test is negative,” said Doron.

A Danish study from late February suggests that reinfection is possible but extremely rare.

The study looked at about 1.8 million cases during the initial wave of the omicron – from late November 2021 to mid-February 2022.

During that time, the researchers said that doctors recorded 187 Covid-19 reinfections — 47 of which were from people who became infected with both BA.1 and BA.2.

This is a very low ratio – 47 out of 1.8 million – which suggests that reinfections are indeed rare. But the data can change the longer we collect it.

Monica Gandhi, a professor of medicine at the University of California, California, said that micron reinfections could become more common than the Danish study suggests. Gandhi said the antibodies provided by the infection or a booster vaccine can only last for about four months. So as that protection wanes, we become vulnerable again.

But that’s not what researchers are seeing in Israel.

Cyrille Cohen, a physician and adviser to the Israeli Ministry of Health, said that data collected in the country indicate that reinfection in a short period of time – that is, within two months – is very rare.

Cohen says that among the 2.5 million people who tested positive for the coronavirus from November to early February, only a few hundred cases of reinfection were observed.

Is BA.2 just another omni?

As with all data on BA.2, the science is also divided as to its origin.

In late February, the World Health Organization (WHO) said in a statement on BA.2 that it “should be considered a variant of concern and that it should remain classified as an omicron.”

Cohen seems to agree – at least with the last point – that BA.2 is another form of omicron. The doctor says that BA.1 and BA.2 are genetically similar. As a result, Cohen said, we are unlikely to see a big wave of BA.2 infections, because many people are already immune to BA.1.

But this, again, is not what other researchers claim.

A Japanese study published in mid-February suggests that there are significant genetic differences between BA.1 and BA.2 – and that they may be greater than we think.

The researchers write that BA.2 is so genetically different from BA.1 that it deserves its own letter of the Greek alphabet – meaning it should be recognized as a variant of the coronavirus.

They found that the BA.2 variant was not more transmissible than BA.1, but also that BA.2 is better at evading existing immunity to the virus.

However, their studies used a BA.2 pseudovirus – rather than the real virus. And that could mean they would get different results if they did similar tests on people.

Vaccination still plays an important role

Vaccines provide a good level of protection against Covid-19. You can still get infected, but you’re less likely to get a serious infection.

As for reinfection, the research was, once again, inconclusive.

A study carried out in Austria in March showed: unvaccinated people who were first infected with the micron developed only antibodies against the BA.1 variant. It is likely, the researchers said, that these people lack protection against other strains of Covid-19.

Meanwhile, another US study showed that people who were vaccinated after contracting BA.1 developed robust antibodies against BA.2.

The study authors say that “the only person who didn’t have [anticorpos] detectable neutralizers was not vaccinated”.

Given all that science still doesn’t know, here’s what appears to be true: Subvariant BA.2 is spreading rapidly and appears to be 30% more contagious than BA.1. It has been circulating in Europe since the beginning of February – excluding Germany, which saw its highest number of infections in mid-March.

In Brazil, according to a study released at the end of March by the Todos pela Saúde Institute (ITpS), the proportion of probable cases of the BA.2 lineage of the ômicron variant rose from 3.8% in relation to the total of positive diagnoses to 27, 2% in three weeks.