The rapidly spreading omicron BA.2 subvariant doesn’t cause significantly more severe disease than the original version, according to a South African study that appears to allay fears it causes harsher illness.
Patients infected with the new subvariant suffered from similar rates of severe disease and hospitalization as those with the original omicron strain, according to researchers from the country’s National Institute for Communicable Diseases that analyzed data from a large hospital group and the government laboratory service, looking at almost 100,000 cases.
The emergence of BA.2 has caused widespread concern as it appears to be even more transmissible than the original omicron strain that was first identified in South Africa and has since spread around the world, leading to waves of infections in the U.S., Europe and elsewhere. The study indicates that, like the original version, BA.2 is relatively mild in comparison with earlier dominant strains, such as delta.
“These data are reassuring,” the researchers said, suggesting that despite BA.2’s competitive advantage, “the clinical profile of illness remains similar.”
Still, the researchers cautioned, South Africa may differ from other locations as most immunity in the country comes from prior Covid infection rather than vaccination. As much as 80% of the population is thought to have been infected, while just 29% of the population has had a full vaccination course and only 1.3% have received a booster. About 72% of the European Union population and 63% in the U.S. have received initial immunizations, and 47% and 27% have gotten boosters, respectively.
The study analyzed cases that occurred as BA.2 rapidly swept through South Africa. At the end of January, 80% of infections in the country were due to the omicron subvariant, up from just 5% in early December.
Among 95,470 infections analyzed by the national laboratory, 3.6% of those with BA.2 were hospitalized, compared with 3.4% of those with the original strain. Among 3,058 hospitalized patients, 30.5% of those infected with BA.2 developed severe disease compared with 33.5% of those with the original omicron version.