The SARS-CoV-2 Omicron strain has been rapidly prevalent worldwide due to its high transmissibility and the evolutionary advantage of the virus.

The Omicron strain carries numerous mutations associated with increased transmissibility and immune leakage.

The strain was recently divided into four sub-variants based on genomic differences, in particular between Omicron strains BA.1 and BA.2.

With the increase in Covid-19 cases due to Omicron sub-variants BA.1 and BA.2, a large number of re-infections have been observed after a previous illness.

This raises the question of whether Omicron BA.2 can escape the natural immunity acquired after infection with Omicron BA.1.

The doctors of the Therapeutic Clinic of the Medical School of the National and Kapodistrian University of Athens (EKPA) Theodora Psaltopoulou, Giannis Danasis, Panos Malandrakis and Thanos Dimopoulos (Rector of EKPA) summarize the relevant pre-publication of M. Stegger and associates: doi: // doi: // doi. org / 10.1101 / 2022.02.19.22271112).

The researchers analyzed a subset of individuals with available clinical data in a Danish database with over 1.8 million cases of Covid-19 diagnosed between 22 November 2021 and 11 February 2022.

Specifically, individuals with two positive samples were analyzed at intervals of at least 20 days but less than 60 days.

A total of 1,739 cases of re-infection were recorded.

Of the 263 cases of re-infection with virus sequencing elements, 47 cases of Covid-19 due to Omicron BA.2 were reported after previous infection with Omicron BA.1.

In addition, 140 cases of Covid-19 due to Omicron BA.2 have been reported following a previous Delta infection.

Most cases involved young, unvaccinated people with a mild illness that did not require hospitalization or lead to death.

In conclusion, this study shows that re-infection with Omicron BA.2 shortly after Omicron BA.1 infection is relatively rare, but can occur.

According to Sarah Otto, an evolutionary biologist at Columbia University in Vancouver, Canada, if the Omicron BA.2 strain prevails in a community shortly after the Omicron BA.1 strain, the immunity offered by the Omicron BA.1 and / or booster vaccination is likely to protect against the Omicron BA surge.2.

Source: National and Kapodistrian University of Athens)