What Do We Know About B.1.621?

It doesn’t yet have a Greek letter to represent it, but the B.1.621 variant of COVID-19 is being eyed closely after its role in a deadly nursing home outbreak in Belgium.

Originally detected in Colombia in January, B.1.621 was recently named a “variant of interest” by the European Centre for Disease Prevention and Control — though neither the World Health Organization nor the CDC has elevated it to this status just yet.

B.1.621 has been detected in the U.S., though it (along with version B.1.621.1) currently accounts for just about 1% of all cases nationally. In Florida, however, recent data from the University of Miami showed that B.1.621 accounted for 9% of cases in the Jackson Memorial Health System as of the second week of July.

Last week, Reuters reported that seven residents in a Belgian nursing home died after being infected with B.1.621, despite the fact that all of them had been vaccinated, though which vaccines they’d received was not disclosed.

All of the deceased were in their 80s or 90s, and some were already in poor physical condition, according to virologist Marc Van Ranst, who conducted tests on the virus found in the nursing home, according to Reuters.

A total of 21 residents had been infected with the variant, along with several staff members. Infected staff only had mild symptoms, Reuters reported.

Overall, B.1.621 accounts for less than 1% of known cases in Belgium, according to Reuters.

Public Health England — which classifies B.1.621 as a “variant under investigation,” just below “variant of concern” — said that as of August 2, there have been 3,854 sequences of B.1.621 reported to GISAID and 32 cases in England, with the majority (19%) being detected in London.

The new variant has mutations in E484K and K417N, making it similar to the Beta variant (B.1.351), so there is concern that B.1.621 could have similar immune escape properties, the agency noted.

In a risk assessment from August 6, Public Health England said that there’s lab evidence of a reduction in pseudovirus neutralization in the serum of people who have either been vaccinated or previously infected with the Delta variant.

However, the agency noted that the variant’s trajectory depends on its growth and expansion, and at the present time there is no indication that it’s outcompeting Delta and it appears unlikely that it’s more transmissible. Still, its immune escape properties could contribute to future changes in growth, they warned, and other epidemiological events could influence whether it becomes established in the U.K.

A recent paper in Lancet Infectious Diseases that assessed rapid genetic sequencing in hospitals found two cases of B.1.621 involving community transmission, at a time when 99% of cases were due to the Delta variant. Both of these cases occurred among unvaccinated individuals.

Delta’s dominance appears to be keeping other variants at bay, at least for now. Last month, concerns were raised about the Lambda variant (C.37) first detected in Peru, but this variant has yet to show up on CDC’s variant tracker, though it has been detected in California and Texas.