As countries wait for cases to subside COVID-19 caused by the Omicron or BA.5 variant, researchers worldwide are on the lookout for what comes next. A sub-variant of the Omicron called the BA.2.75 or Centaurus rose rapidly in India. Some scientists are sounding the alarm, while others say the variant is unlikely to spread widely. In an article, recently published in the prestigious international scientific journal Nature, the relevant data are presented.
The professors of the School of Medicine of the National and Kapodistrian University of Athens, Theodora Psaltopoulou (Professor of Therapeutics-Epidemiology-Preventive Medicine), Stavroula(Lina) Paschou (Assistant Professor of Endocrinology), Evangelos Terpos (Professor of Therapeutics-Hematology), Thanos Dimopoulos (Professor of Therapeutics- of Hematology-Oncology and Rector of EKPA) and the professor of the Department of Biology of the National and Kapodistrian University of Athens Yannis Trougakos, summarize the main points of this article.
The BA.2.75 or Centaurus sub-variant has been detected in more than 20 countries worldwide, but is growing rapidly mainly in India. Researchers there have sequenced more than 1.000 samples of the variant since May. Data indicate that approximately two-thirds of new cases in this country are currently caused by BA.2.75. This variant appeared to have a transmission advantage over the BA.5.
A series of studies have shown that the two variants, Omicron 5(BA.5) and Centaurus, have roughly similar abilities to evade immunity provided by infection and vaccination. This suggests that Centaurus may not push cases to much higher levels outside India, at least not while population immunity is high and before the variant shows many additional mutations.
So far, BA.2.75 has been detected at relatively low rates outside of India, in countries such as Japan, the United States and the United Kingdom, which are in the middle of or just past the peaks of increases driven primarily by BA.5. We are reaching a point where these variants are somehow competing with each other and are almost equivalent. Thus, people who had BA.5 are not likely to have a significant infection with BA.2.75 and vice versa.
Laboratory studies published very recently (mostly as preprints) support this idea. Indeed, the two variants have a similar ability to evade antibodies induced by vaccination and prior infection. In 2021, India experienced an explosive wave of cases caused by the Delta variant, which shares a core mutation with BA.5. Presumably, previous Delta infections provide additional protection against BA.5, leaving a margin for BA.2.75. It is hypothesized that some countries may end up having a different mix of Omicron sub-executives prevailing compared to other countries.
From the data in India, Centaurus does not yet appear to increase hospitalization or death rates there. The combined effects of high vaccination rates and previous infection certainly help. This hybrid immunity will largely protect and keep people out of hospitals.
But while BA.2.75 hasn't spread widely yet, it could do so in the future. Some sequences of BA.2.75 include a mutation found in BA.5 called L452R, which could unfortunately increase the subvariant's ability to reinfection. Even if hospitalization and death rates remain low in a wave caused by the Centaurus variant, the high frequency of new waves of infection could mean more people with long COVID-19 (i.e. persistent symptoms after 3 months of diagnosis) and more generally, maintaining the burden on health systems internationally.
Source: RES-EAP