People infected with Omicron unlikely to catch BA.2 shortly afterward, study suggests

Reinfections from the sub-variant BA.2 can occur shortly after a person has caught Omicron but are rare, new research suggests.

The study, which looked at 47 cases of BA.2 infection that came shortly after an Omicron infection, found that this phenomenon disproportionately affects unvaccinated people.

BA.2 is a spin-off from the Omicron variant, known as BA.1, but appears to be 1.5 times more infectious than its predecessor and is on course to become dominant in the UK. However, scientists have said there is no indication that BA.2 is more deadly or better at evading immunity than Omicron.

Now, researchers from Denmark have highlighted how, out of 1.8 million cases reported between 21 November 2021 and 11 February 2022, just 1,739 fulfilled the criteria of two positive samples separated by 20 to 60 days.

Of these, 263 paired samples were randomly selected and analysed. The research found 187 (71 per cent) cases of reinfections, 47 (18 per cent) of which were BA.1-BA.2 reinfections.

“The reinfection rate appears to be low given the high 258 number of positive Sars-CoV-2 tests during the study period,” the authors wrote.

Out of the 47 cases, 42 were unvaccinated (89 per cent), suggesting people who have not been jabbed are more likely to catch BA.2 shortly after a BA.1 infection.

Many of these reinfections were observed in people under the age of 30, the researchers said.

Reinfections were characterised by overall mild symptoms comparable to the initial infection and did not lead to hospitalisation or death, according to the study.

“It is, however, striking that mainly children and adolescents become reinfected, since children to a higher degree than adults develop a sustained cross-reactive immunity,” the authors note.

“This may be explained by the very high incidences among children in the chosen study period, whereas adults and elderly had lower incidences.”

The study has not yet been peer-reviewed and comes as BA.2 continues to spread across multiple countries.

In the US, the Omicron sub-variant has now been detected in more than 30 states, makes up around 3.9 per cent of new infections, and appears to be doubling quickly, according to the Centers for Disease Control and Prevention’s data tracker.

“If it doubles again to 8 per cent, that means we’re into the exponential growth phase and we may be staring at another wave of Covid-19 coming in the US,” Samuel Scarpino, the manager director of pathogen surveillance at the Rockefeller Foundation, told NPR.