New Coronavirus News from 22 Feb 2022

COVID-19 Scan for Feb 22, 2022 [CIDRAP, 22 Feb 2022]

Study highlights rare BA.2 subvariant reinfections after Omicron COVID-19

Infection with the SARS-CoV-2 Omicron BA.2 subvariant shortly after an initial infection with the Omicron BA.1 subvariant—the original Omicron strain—is rare, occurring mostly in young, unvaccinated people with mild symptoms, according to a non–peer-reviewed Danish study.

In the study, published today on the medRxiv preprint server, researchers at the Statens Serum Institut in Denmark analyzed the subgenomic and genomic RNA of viruses responsible for a randomly selected group of 263 paired samples from more than 1.8 million COVID-19 patients. The study period was Nov 22, 2021, when Omicron was first identified in that country, to Feb 11, 2022. The BA.2 variant now accounts for most COVID-19 cases in Denmark.

Of the 263 virus samples, 187 COVID-19 reinfections (71%) were identified, 47 (18%) of which were BA.2 cases after initial BA.1 infections. The severity of both types of infections was similarly mild, and no patients were hospitalized.

Median patient age was 15 years, none were older than 38, 89% were unvaccinated, 6% had received two COVID-19 vaccine doses, and 4% had received one dose.

Overall, viral load was significantly lower in patients with BA.2 reinfections than during the initial infection.

"This may indicate a more superficial and transient secondary infection that could be explained by T cell-mediated immunity obtained during the first infection," the researchers wrote.