BA.2, a somewhat more contagious version of omicron that does not escape vaccination

On January 25, the World Health Organization (WHO) recommended investigating BA.2, a subvariant of omicron that has at least 40 different mutations compared to the original. What is known so far about this new version? Is it more transmittable? Does it cause a more severe COVID-19? And the vaccines, do they work?

In some countries such as Denmark or the United Kingdom, their presence has increased a lot in recent days, but it is still early to know why. However, data are beginning to emerge that point to greater transmissibility.

Iñaki Comas, a scientist at the Valencia Institute of Biomedicine (eastern Spain) and who was director of the SeqCovid-Spain consortium, which sequenced thousands of SARS-CoV-2 samples, details its characteristics to Efe and assures not to share that there is talk of silent or stealthy: “it is as stealthy as the delta or the other variants”.

Is the BA.2 very different from the original omicron?

They’re quite different, they’re not that close genetically: they’re about as far apart from each other as alpha was from beta or delta. In BA.2, 40 different mutations have been found in its entire genome with respect to the original, in addition to a few in the spike, the protein that the coronavirus used to enter the human cell.

However, many of the variations in the spike or protein S “we do not know what they do”, neither in this subvariant nor in the original one, so it is difficult to know the meaning of the differences.

Is BA.2 more transmissible than the original version?

In countries that have good surveillance, such as Denmark or the United Kingdom, BA.2 is increasing in frequency, indicating that it has some advantage in transmissibility. According to preliminary studies carried out by the Danish authorities, this could be 1.5 times more transmissible than BA.1, although there are still many things to know.

For example, there is a lack of data on whether this subvariant can infect people who have previously been infected by the original omicron; “Probably not for a while, but we don’t know yet,” says Comas, who points out that “the feeling is that this subvariant is not going to change much the management of the current wave of the pandemic.”

Does it cause a more severe COVID-19?

Preliminary data from the United Kingdom and Denmark indicate that no, there are no differences in this regard and, in any case, if there were, the original would be more serious, but it is difficult to establish this.

Is it usual for subvariants to appear?

Viruses always mutate, within their biological process, and replicate. Although there are correction mechanisms in this copying system, these sometimes fail, causing an accumulation of errors or mutations that can lead to a new variant.

Many are not especially different. In two years hundreds have appeared and only a few -alpha, beta, gamma, delta and omicron- have been classified as worrying by the World Health Organization, for being more transmissible, for their ability to skip the first barrier of the response immune (neutralizing antibodies) and, in the case of delta, also because it is more severe.

“The vast majority of variants and subvariants have come and gone and the latter have not been very different from their sisters. The authorities have now looked at BA.2 because it seems to have an advantage in transmissibility, which is why it is under investigation.”

Comas recalls that the origin of ómicron remains unknown, although there are several hypotheses; the one that has more strength is that its evolution occurred in a very immunosuppressed person infected with covid-19 for a prolonged period of time. By not having a strong system, the virus was able to become chronic and mutate continuously.

“This leads us to a second reading: health has to be global or it is not health. If we had helped, for example, to make HIV chronic as has been done in developed countries, we would now have fewer problems controlling the emergence of SARS-CoV-2 variants.”

Is the effectiveness of the vaccines the same?

According to a report from the British health authorities on January 27 and after a comparative analysis, the effectiveness of the vaccines against symptomatic disease was similar for the two subvariants.

Effectiveness increased to 63% for the original version and 70% for BA.2 at two weeks of booster shots.

Do antigen and PCR tests detect BA.2?

This subvariant and all variants are detected by antigen and PCR; that is, the coronavirus is detected but “without a last name”. To investigate the latter, the patient’s sample must be sequenced.

What happens is that there is a specific type of PCR with which it can be suspected whether it is BA.1 or not (the same thing happened with alpha). These tests use three targets for diagnosis, in case one fails. Precisely BA.1, due to one of its mutations, causes one of the targets to fail, which is why it is intuited that it is this version and not another.

“I don’t know where the silent thing came from. BA.2 is as stealthy as delta or other variants”, he concludes.