Omicron 2 variant, is it more contagious but also more lethal? – breaking latest news

Omicron’s sub-variant, BA.2, informally called Omicron 2, is steadily increasing worldwide (reported in 43 countries) and, according to the latest monitoring by the World Health Organization, accounts for 21% of Omicron cases. Ten countries reported the predominance of BA.2 (above 50%) including China, Philippines, India, Nepal, Denmark, where it reached 66%. In Italy it represents 3% of cases.

How transmissible?

Early studies indicate that BA.2 is more transmissible than BA.1. Estimates in Denmark and Great Britain indicate that Omicron 2 is between 30% and 50% more transmissible than Omicron. In a Danish study of 8,000 families, it was found that unvaccinated primary cases infected with BA.2 are more likely to pass the virus to family members than those infected with Omicron. However, even those who completed the vaccination course were more vulnerable to the BA.2 variant than the BA.1.

Omicron 2 grows both in countries where there is a decline in the pandemic wave and in those where there is growth and this data supports the hypothesis that the reason for the growing diffusion is due more to greater transmissibility than to a immune evasion from the vaccine or previous infection. A pre-press laboratory study confirms this hypothesis.

The most serious disease?

There is currently limited evidence on possible differences in BA.1 and BA.2-induced disease severity. In the UK where BA.2 has risen steadily in recent weeks there has been a decline in hospitalizations and deaths. An analysis conducted in Denmark showed no differences in the risk of hospitalization between people infected with BA.1 or BA.2, although there has been an increase in the number of hospitalizations and deaths in the country since Omicron 2 became dominant. However, the variant does not appear to cause more serious disease, even in children. In Nepal, where Omicron 2 prevails with very high percentages, the number of hospitalizations, even in intensive care, is decreasing. The same is true for South Africa where BA2 at 86% and hospital admissions continue to decline.

A Japanese laboratory study published in pre-print just three days ago concludes that it could cause a more serious disease. The researchers infected hamsters with BA.1 and BA.2. animals infected with BA.2 became more severely ill and had more impaired lung function. According to Japanese scientists, Omicron has virological and pathogenic characteristics that distinguish it from the previous strain and should therefore be considered a variant of concern in itself. Their analysis also found that the reproduction rate of BA.2 would be 1.4 times higher than that of the previous strain, and that the new Omicron sub-variant appears to be more replicative in human nasal epithelial cells than BA.1.

Are vaccines effective?

Several studies suggest that BA2 can easily overcome immunity induced by vaccination or a previous infection with other variants, but not much unlike what Omicron is already doing compared to the variants that preceded it. Indeed, some studies carried out in the UK and Denmark even show a greater ability of the vaccine to prevent Omicron 2 than 1. Data from the UK indicate that administering a booster dose two weeks after the second vaccine dose showed a 63% efficacy in the prevention of symptomatic disease caused by BA.1 and 70% in the case of BA.2 but the efficacy data decrease over time (in both variants).

However, the results of the studies conducted so far are not unambiguous. A pre-print work led by virologist David Ho of Columbia University in New York City confirmed that BA.2 and BA.1 have similar abilities to resist neutralizing antibodies in the blood of people who had been vaccinated or previously infected. But Ho’s team reported that genetic mutations unique to BA2 affect how some antibodies recognize the variant. Some antibodies are in fact less effective at neutralizing BA2 than BA1, while, conversely, another type of antibody tends to be more active than BA2. But there is unlikely to be any greater risk with BA2 than BA1 says.And the aforementioned February 15 preprint led by virologist Kei Sato, of the University of Tokyo, found that vaccinated hamsters and mice infected with BA.1 produced less potent antibodies against BA.2 versus BA.1.

Could Omicron 2 lead to a new pandemic wave?

Scientists think BA.2 is unlikely to trigger a second major wave of infections, hospitalizations and deaths following the Omicron wave. However, the variant could create greater problems in countries with low vaccination rates.

Omicron’s sister could prolong the pandemic wave. But our data suggests there won’t be a new surge, Dan Barouch, an immunologist and virologist at Beth Israel Deaconess Medical Center in Boston who conducted a pre-press study, told Nature. In this case the neutralizing antibodies induced by three doses of Pfizer vaccine have been shown to be slightly better at preventing Omicron 1 than Omicron 2 But this small difference in immunity avoidance is unlikely to explain the rise of BA2 around the world, Barouch points out.

Can Omicron 2 infect those healed by Omicron?

It is not yet clear whether the BA.2 variant is different enough to cause reinfection in people who have been infected with Omicron. We know that those recovered from Omicron can feel quite calm because contagion with the same variant is considered highly unlikely since specific antibodies have developed. But Omicron 2 is not the same virus: it shares 38 mutations with BA.1 but has an additional 27 unique mutations. Researchers from Israel have identified a handful of cases in which people cured of BA.1 subsequently became infected with BA.2. The State Serum Institute in Copenhagen has started a study to determine how often these reinfections occur. Troels Lillebaek, leading the research, says he would be surprised to find that there is no protection: I think reinfection is unlikely, but we’ll find out in a few weeks.

What is the time of onset of symptoms?

From a preliminary UKSA survey, based on UK tracing, the mean time to onset of symptoms appears to be about half a day shorter for BA.2 than for BA.1, with an average period of 3 respectively. , 27 days compared to 3.72 days. With Delta, the interval between infection and the onset of symptoms was approximately 4 days. The shorter incubation time could contribute to the increase in the growth rate of BA.2

Do the cures work against Omicron 2?

A preliminary laboratory study found that BA.2 resistant to the monoclonal antibody sotrovimab, the only one so far deemed effective against Omicron. On February 9, Vir Biotechnology, which together with Glaxo produces the drug, declared that the experiments conducted by the pharmaceutical company and not yet widespread, suggest that the monoclonal is also effective against Omicron 2. There are still no data regarding the effectiveness of antiviral drugs. .

Do the swabs detect Omicron 2?

Omicron 2 has also been defined as invisible because it is difficult to identify, given that it does not have the deletion of the S gene characteristic of Omicron BA.1: to find it, therefore, it is necessary to sequence all the samples and this implies a laboratory capacity that not all countries have. . The lack of the S gene, on the other hand, allows one to suspect the belonging of a sample to the Omicron variant of the classic type directly from the swab (without sequencing, which is done later).