London, Feb 23 While the chances are rare, reinfection with BA.2 can occur shortly after initial BA.1 infection, according to a study by Danish researchers.
The Omicron variant can be divided into 3 subtypes: BA.1, BA.2 and BA.3.
The BA.1 subtype of Omicron is more prevalent than the other subtypes, but BA.2, is gaining ground in many places worldwide, particularly in Europe and Asia.
In a yet to be peer-reviewed study, researchers at Denmark's Statens Serum Institut (SSI) showed that infection with two different Omicron subtypes is possible.
This seems to occur relatively rarely in Denmark, and reinfections have mainly affected younger unvaccinated individuals, they said
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 and 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.
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.
In November last year, South African researchers showed higher-than-expected rates of reinfection compared with those of previous waves, Nature reported.
Similar trends have now been documented elsewhere.
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.
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