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The more contagious subunit of amicron, known as BA.2, is spreading around the world and may soon become the dominant version of Covid-19.
It is now a major option in at least 18 countries and is spreading rapidly, accounting for 35% of all new cases that have been genetically sequenced worldwide, compared to 10 countries and 21% of cases the week before, according to new data from the World Conservation Organization. health. . In the US, BA.2 is currently 3.8% genetically sequenced Coronavirus covid infection cases, according to the Centers for Disease Control and Prevention.
The pandemic-weary public wants to know two main things: will BA.2 cause a second outbreak of omicron cases and put even more people in the hospital with severe infections? So far, scientists say the answer to both questions is probably no.
However, Danish scientists confirmed this week that the new variant could re-infect people who had previously been ill with omicron, although this does not seem to be the case often. They also agree that it is more contagious than the original version of the micron, BA.1, which is still widespread around the world.
But surprisingly, this does not stimulate a second wave of omicron infections. Globally, the number of Covid cases has fallen by 21% in the last week – declining in every region except the western Pacific – while the death rate has fallen by 8% in the last week, according to the WHO.
Maria Van Kerchowe, WHO technical director for COVID-19, said the World Health Agency was closely monitoring the countries where BA.2 was detected, but so far the sub-option has not caused a new surge in cases.
“As we see such a decrease in the number of cases in the countries, we do not see an increase again with BA.2,” Van Kerch said during a question-and-answer session that was broadcast live on WHO’s social media platforms on Tuesday.
Here’s what’s known about the sub-option so far.
Danish researchers found that BA.2 is about 30% more transmitted than BA.1. Denmark was one of the first countries where BA.2 became dominant, and health authorities around the world paid close attention to the situation in that country to find out what the potential for a future pandemic could mean.
“We conclude that Omicron BA.2 is inherently much more transmissible than BA.1,” said a group of scientists linked to the Danish health authorities and the University of Copenhagen. wrote in a study last monthwhich has not yet passed the expert review.
UK Health Agency found in late January that BA.2 had a significant advantage over BA.1 in England. “We now know that BA.2 has an increased growth rate that can be seen in all regions of England,” said Dr Susan Hopkins, the agency’s chief medical adviser.
“If what is reported is true that BA.2 is slightly more transmitted, then I am inclined to say that BA.2 is likely to prevail wherever BA.1 is,” said Mehul Sutar, a virologist with Emory University.
However, Sutar said this does not necessarily mean that BA.2 will cause an outbreak of infection. BA.2’s ability to cause another wave depends in part on whether it can re-infect people who have already been infected and cured of the omicron, he said.
Danish scientists confirmed on Tuesday that sub-variant BA.2 could re-infect people who previously had its predecessor omicron, BA.1, although the risk of catching the virus again looks low.
The Statens Serum Institute in Copenhagen analyzed a randomly selected sample of 263 cases of re-infection. According to the study, forty-seven people became infected with BA.2 less than two months after becoming infected with BA.1. Most people re-infected with BA.2 after BA.1 were under 20 years of age and had not been vaccinated.
“The re-infection rate appears to be low given the large number of positive SARS-CoV-2 tests during the study period, but still emphasizes the need for continuous assessment of the duration of vaccine-induced immunity and / or innate immunity,” wrote the study authors.
The reinfected people had mild symptoms and none of them were hospitalized and died. The study also found that people re-infected with BA.2 had a reduced viral load, indicating cross-immunity from the first infection.
The UK Health Agency in a separate study identified 69 cases of people re-infected with BA.2 no more than 90 days after the first infection with Covid. However, among the 51 cases where sufficient information was available, no case of re-infection of BA.2 after the first BA.1 infection was found. The timing of the first infections and the sequence showed that their initial Covid cases were delta-variant.
No study has been peer-reviewed, which is the gold standard in academic publication. Scientists are publishing their research as soon as possible due to the urgency of the pandemic.
World Health Organization, in a statement Tuesdaysaid, data from early cases of reinfection in the general population show that a single BA.1 infection provides strong protection against re-infection with BA.2.
“It’s possible that BA.2 has, in his view, an unfortunate scenario of coming into a population that has a lot of pre-existing immunity that targets him, and that may be part of the reason why we don’t see it growing as fast as omicron BA.1, ”said Andrew Pekash, a virologist at Johns Hopkins University.
Great, real-world research in South Africa which has also not yet been tested, found that BA.2 causes a disease similar to omicron BA.1, which does not usually make people as sick as the delta variant. In other words, BA.2 does not usually cause more severe disease.
The National Institute of Infectious Diseases of South Africa found that 3.6% of people with BA.2 were hospitalized compared to 3.4% of people with BA.1. About 30% of patients hospitalized with BA.2 were severely ill compared to 33% of patients hospitalized with BA.1. The study is based on more than 95,000 people who took the Covid test from December to January.
“BA.2 in terms of clinical severity behaves very similarly to BA.1 with reduced clinical severity compared to previous options and in particular the delta,” said Cheryl Cohen, one of the study’s authors, at a press conference broadcast live on YouTube earlier.
WHO representatives have repeatedly said that there is no signs of BA.2 is more severe. Cohen said the data from South Africa was encouraging, but she also warned that no conclusions could be drawn about other countries based on the results.
“We need to be careful when extrapolating to other places, especially to other countries where most of the immunity is derived from vaccination, as opposed to South Africa, where most of the immunity comes from a natural infection,” Cohen said. “A natural infection can potentially provide more reliable protection against BA.1 and BA.2 than vaccination.”
At least one study found that mutations in the BA.2 thorn protein caused a more severe lung infection in hamsters than BA.1. The virus uses thorns to invade cells, and vaccines target this protein to block infection. A team of Japanese scientists who led the study said that as a result the WHO should consider appointing BA.2 a separate option of concern.
Sutar, a virologist with Emory, urged caution when interpreting the results of the Japanese study because it does not use the true version of BA.2. He said mutations in one component of the virus, such as thorns, do not necessarily determine whether a virus is more severe.
The study did not undergo an expert review, and one scientist said the results may not hold true in the real world because they used the developed version of BA.2 to test their theory. According to Takashi Ira, one of the study’s authors, the team took the BA.2 adhesion protein, replaced it and placed it on the original Wuhan virus. Airy in an email to CNBC acknowledged that more reports show no increase in the severity of BA.2 compared to BA.1.
“Therefore, the conclusion of our study that BA.2 is more pathogenic than BA.1 may not reflect the real results of an isolated virus,” Airy writes. However, he said the results of the study do show that mutations at the peak of BA.2 are capable of causing more severe infection.
A a separate study from Japan, who isolated the BA.2 virus from a traveler who arrived in Japan from India, found that the subvariant had a similar severity level to BA.1 in mice and hamsters. The study was also not reviewed.
The WHO Covid Options Advisory Group reviewed both South African and Japanese studies, among others, before determining that BA.2 should remain classified as omicron rather than labeling it as a separate variant of the problem. This suggests that WHO does not currently view BA.2 as a greater threat to global health than omicron as a whole.
The original strain of omicron BA.1 demonstrated a significant ability to avoid vaccine-induced antibodies, leading to many breakthrough infections during the recent outbreak. Danish scientists have found that BA.2 evades vaccine protection better than BA.1, according to the study is published last month.
However, vaccinated people who become infected with breakthrough infections are not as likely to spread the virus to others as unvaccinated people, according to the study. This is probably because people who have been vaccinated have a lower viral load than people who have not been vaccinated, the researchers said. In other words, vaccines still help reduce the spread of the virus.
Scientists from Beth Israel Deaconess Medical Center in Boston have found that BA.2 evades antibodies from two doses PfizerThe vaccine’s slightly larger than BA.1. The level of neutralizing antibodies was approximately 1.4 times lower compared to BA.2, according to a study published in early February.
“BA.2 evades antibodies from Pfizer vaccines similar to BA.1, perhaps a little more, but not much more,” said Dan Baruch, study author and principal investigator at the Harvard Center for Virology and Vaccine Research. Baruch also helped to develop Johnson and JohnsonVaccine against Covid.
Baruch said that vaccinated people infected with BA.1 also produced strong antibodies against BA.2. “This suggests that because omicron BA.1 was very common, these people probably have a significant degree of immunity to BA.2,” he said.
The UK Health Agency in a report published on 24 February also found that the effectiveness of two doses of a symptomatic vaccine had fallen to a similar level against BA.1 and BA.2. Enhancement injections increased protection to 69% against BA.1 and 74% against BA.2 two weeks after the third dose, according to a UK study.
Correction: The Statens Serum Institute in Copenhagen analyzed a randomly selected sample of 263 cases of re-infection. In the previous version, the name of the institute was misspelled.