Omicron variant: BA.2 may lead to more severe diseases?

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Omicron variant: BA.2 may lead to more severe diseases?

Upgraded Omicron causes more serious illness? New research sounds alarm bells.

At present, European and American countries have gradually released anti-epidemic measures. One of the reasons is that the virulence of Omicron has decreased.

But a new Japanese study found that the new sub-variant BA.2, known as an upgraded version of Omicron, may not be as toxic as everyone thought.

On February 15, Japanese researchers published a study on the preprint bioRxiv, saying that BA.2 may be the same as the old variant of the new coronavirus, including Delta, which can cause severe disease, and will also spread further around the world. The article even proposes that BA.2 should be given a new Greek letter to distinguish it from Omicron BA.1.

This result has aroused everyone’s attention: since February this year, the number of BA.2 global infections has continued to rise, and it has also entered China. According to the Shenzhen Health and Health Commission, in several transmission chains/points of the Shenzhen epidemic, the source of the infection virus is Omicron BA.2.

Omicron variant: BA.2 may lead to more severe diseases?

BA.2 may lead to more severe disease

Previously, the academic community agreed that the transmission power of BA.2 was about 1.4 times that of BA.1, but there was no evidence to clarify the difference in virulence between the two.

The Japanese researchers conducted a hamster infection experiment for comparison.

The researchers found that after infection, the RNA load of BA.2 in the periphery of hamster lung was significantly higher than that of BA.1, which was 9.3 times. Over time, the relevant expression of BA.2 viral RNA could still be continuously detected in lung tissue, while the level of BA.1 was much lower and gradually disappeared.

Meanwhile, BA.1-infected hamsters showed no or only mild disease symptoms. But BA.2 was different, and the hamsters it infected showed weight loss and symptoms of respiratory disease.

BA.2 spreads faster and more efficiently in lung tissue than BA.1, the researchers said. According to all histopathological parameters of hamsters infected with BA.2, the levels of bronchitis, hemorrhage, and alveolar damage were significantly higher than those infected with BA.1.

This suggests that BA.2 may be more pathogenic than BA.1. “It’s probably a stronger virus than BA.1, and it’s more transmissible and causes more severe disease,” said Dr. Daniel Rhoads, chief of the department of microbiology at the Cleveland Clinic in Ohio.

“herd immunity” after infection, may not be so effective

The number of people with acquired immunity after infection is relatively large, which is one of the strengths of European and American countries.

As the dominant strain of the global pandemic, BA.1 can prevent the people it has infected from being attacked by BA.2? Japanese researchers analyzed the sera of 17 patients who had been infected with the BA.1 virus and recovered, and the results showed:

The BA.1 convalescent sera showed strong antiviral effect against the BA.1 strain, but it seemed to be less effective in BA.2, which was 1.4 times more resistant to sera than BA.1. The researchers repeated the experiment on mice and came to similar conclusions:

Compared with BA.1, the resistance of BA.2 to hamster serum in convalescent period of BA.1 infection was significantly increased by about 2.9-fold.

The researchers also obtained antiserum by immunizing mice with the S protein of BA.1, and using the mouse serum neutralization assay, the results showed that the resistance of BA.2 to immune serum was 6.4 times higher than that of BA.1.

Not to mention those who were infected early in the pandemic.

Studies have shown that BA.2, like BA.1, is highly resistant to convalescent serum whether it is the original strain, Alpha or Delta.

A simple understanding is that no matter whether you have been infected with other mutants early or recently infected with BA.1, facing BA.2 again may not be as “safe” as you think.

Do vaccines still work? What about antiviral drugs? In this regard, BA.2 continues the ability of BA.1, and it seems to be slightly better.

Experiments with pseudoviruses and vaccination-elicited neutralizing antibodies showed that BA.2 was highly resistant to both mRNA and adenovirus vaccines. In addition, BA.2 was almost completely resistant to two therapeutic monoclonal antibodies, Casirivimab and Imdevimab.

Omicron variant: BA.2 may lead to more severe diseases?

British academics question the government: Relaxing epidemic prevention should provide scientific basis

But mouse experiments do not fully reflect the actual situation, and there are certain differences between the pathology and infection kinetics of the virus between humans and laboratory animals.

Back in the real world, the evidence on the severity of BA.2 is mixed. Hospitalizations continued to decline in countries where the outbreak was on hold, such as South Africa and the United Kingdom. But in Denmark, BA.2 has become the main source of infection, and the number of hospitalizations and deaths is on the rise.

This research is more like a wake-up call for us. Deborah Fuller, a virologist at the University of Washington School of Medicine, believes that establishing a system to specifically test for BA.2 will be the first thing many countries need to do.

Distinguishing BA.1 and BA.2 requires whole-genome sequencing, which is a relatively time-consuming and labor-intensive process. In a country where the number of cases is increasing by tens of thousands, it is not easy to obtain relevant data and analyze it in time.

“Have humans outperformed the virus now? I don’t think the epidemic prevention regulations can be lifted until the relevant data comes out,” said Professor Deborah Fuller.

Penelope Toff, chairman of the British Medical Association’s branch of public health medicine, said recently that the number of confirmed cases is still very high, with hundreds of deaths every day, but the UK has lifted epidemic prevention measures such as self-isolation. “We have the right to question whether there is a scientific basis behind the government’s decision.”

Lawrence Young, a virologist at the University of Warwick, believes the pandemic is not over.

“If there’s one thing we’ve learned over the past two years, it’s that the impact and future of Covid-19 remains unpredictable,” said Lawrence Young.

References;
[1]Covid-19:Show us evidence for lifting restrictions,doctors tell Johnson，https://www.bmj.com/content/376/bmj.o383

Omicron variant: BA.2 may lead to more severe diseases?

(source:internet, reference only)

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