Omicron Subtype Reinfection Possible, Warn Experts

Early data suggests the BA.2 Omicron subtype is around 1.5 times more infectious than BA.1, which is the most common subtype in the US. | Credit: Joe Raedle

Danish study says that in rare cases, BA. 2 infection can happen soon after BA. 1.

Tanya Savkoor

Reinfection with the BA.2 subtype of Omicron variant of the coronavirus can occur shortly after initial BA.1 subtype infection, according to a study by researchers at Denmark’s Statens Serum Institut (SSI).

The Omicron variant can be divided into 3 subtypes: BA.1, BA.2 and BA.3. While the BA. 1 subtype is more prevalent, BA.2, is gaining ground in many places worldwide, particularly in Europe and Asia.

The yet to be peer-reviewed study Danish researchers said that reinfection seems to occur relatively rarely in Denmark, and have mainly affected younger unvaccinated individuals. 

The team studied how many individuals have had two positive tests and used genome sequencing to investigate the virus variants with which they had become infected. They found 67 cases in which the same individual had become infected twice at a 20-60-day interval, where both infections were due to Omicron subtypes.

In 47 of the cases, the affected individual first became infected by BA.1 and then by BA.2. The majority of the infected were young and unvaccinated, and most experienced mild symptoms during their infections.

The difference between the severity during their first and second infection was negligible. None of the infected individuals had become seriously ill, and none required admission to hospital, the researchers said.

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Reinfections from Omicron have been shown in various studies.

A recent study by the Imperial College London has shown that the risk of reinfection with the Omicron coronavirus variant is more than five times higher than other strains.

Data collected by the UK Health Security Agency showed that more than 6,50,000 people have probably been infected twice in England; most of them were reinfected in the past two months, the report said. Before mid-November, reinfections accounted for about 1 per cent of reported cases of Covid-19, but the rate has now increased to around 10 per cent.

The UK Office for National Statistics in Newport has also seen a sharp increase in possible reinfections in recent months, as part of its random sampling of households across the country.

“Such surveys could be underestimating the true rate of reinfection because some infections go undiagnosed, and some could have happened sooner after the first infection – especially in countries where cases of Omicron quickly followed a Delta wave,” Catherine Bennett, an epidemiologist at Melbourne’s Deakin University said.

According to Bennett, multiple factors could explain the spike in reinfections. With more people now already exposed to the virus, there is a higher chance of seeing reinfections, she said. She added that the Omicron variant’s speedy spread and its ability to evade immunity is probably playing a part.

With inputs from IANS