Danish study finds it is ‘rare’ to be reinfected with Omicron subvariants

Getting infected twice with two different Omicron Covid-19 subvariants is possible, but rarely happens, a Danish study has found.

In Denmark, a more infectious sublineage of the Omicron variant known as BA.2 has quickly dethroned the “original” BA.1 variant, which is the most common worldwide, but it remains unclear whether a person can be infected by both variants.

A new study led by researchers at Denmark’s top infectious disease authority, Statens Serum Institut, shows people infected with BA.1 can get infected with BA.2 shortly afterwards, but it is a rare occurrence.

“We provide evidence that Omicron BA.2 reinfections are rare but can occur relatively shortly after a BA.1 infection,” the study authors said.

BA.1 and BA.2 differ by up to 40 mutations. While BA.2 accounts for more than 88% of cases in Denmark, cases have started to increase in the UK, SA and Norway.

The reinfections mostly affected young and unvaccinated individuals and caused mild disease, none of which led to hospitalisations or deaths, the researchers said.

The study, which is not yet peer reviewed, found 1,739 cases registered between November 21 2021 and February 11 this year, where people had tested positive twice between 20 and 60 days apart.

During that time more than 1.8-million infections were registered in Denmark.

From a smaller sample group, the study found 47 instances of BA.2 reinfections shortly after a BA.1 infection. The researchers also detected less virus material in the second infection, suggesting some immunity was developed from the first infection.

Reuters