Covid-19

Omicron BA.3: What WHO Says About Covid Severity Signals In People

Published

1 year ago

March 6, 2022

The World Health Organization (WHO) has said it is tracking several sublineages of Covid variant Omicron, including BA.1, BA.1.1, BA.2, and BA.3. They are also investigating whether these Omicron subvariants cause “more severe disease” within hamsters under similar experimental conditions.

“Omicron is a variant of concern, and we track Omicron in several sublineages. The most common ones detected worldwide are BA.1, BA.1.1, and BA.2. BA.3 and other sublineages are also detected,” WHO’s top infectious disease expert Maria Van Kerkhove said.

Many people have heard of a Japanese study that came out as a preprint. This is an experimental study looking at hamsters in particular. Specifically, they were looking at whether or not experimentally within hamsters there was a signal of causing more severe disease. “We also look at severity in the real world,” she said.

The WHO is also looking at severity signals in people, according to Kerkhove. Is there any difference in severity at a population level between people who contracted BA.2 and those who contracted BA.1? We are not seeing a difference in the severity of BA.1 compared to BA.2 in this evaluation from several countries, she maintained.

What Japanese lab study says:

Researchers have recently found that Omicron subvariant BA.2 causes more severe diseases than Omicron subvariant BA.1. Japanese researchers investigated if Omicron BA.2 causes severe diseases in hamsters. According to the preprint, BA.2 may cause severe disease in hamsters.

However, when evaluating severity signals in humans, there was no increased risk of hospitalization among those who had been infected with BA.2 compared to BA.1.

Key things Japanese study said about Omicron BA.2:

The subvariant BA,2, also known as stealth Omicron, that was identified by the Japanese team was characterized by the following:

1) BA.2 appears to be capable of causing “serious illness.” It shows immune escape properties just like sub-variant BA.1. Further, “stealth Omicron” is resistant to treatment with monoclonal antibodies.

2) Despite BA.2 being classified as an Omicron variant, its genomic sequence is very different from BA.1. “This suggests that BA.2 has different virological characteristics from BA.1,” the study said.

A WHO report later clarified that the stealth omicron can cause serious infection in hamsters, but studies among humans have shown that the severity is the same for both subvariants.