New research has made the focus of the BA.2 variant clearer.Connecticut News

(CNN)-Following new laboratory and animal studies suggesting that BA.2 may cause more serious illness than the original Omicron strain, two new studies have shown that human immunity is on this strain. It helps to show how well you are defending against the real world.

BA.2 is about 30% improvement in infectivity Early studies in the United Kingdom and Denmark show that it is more than the original Omicron variant, BA.1, and currently causes one-fifth of Covid-19 cases worldwide, according to the World Health Organization.

Although the number of cases of Covid-19 is decreasing worldwide, the relative proportion of cases with BA.2 is increasing.Surpasses the original Omicron strain At least 43 countriesPromotes the fear of another catastrophic pandemic wave.

“I don’t think we need to ring the global alarm for now, but I think we need to pay attention to BA.2 as it seems to have a growth advantage over BA.1.” Says Dr. .. Dan Barouch, director of the Virology and Vaccine Research Center at the Beth Israel Deaconess Medical Center in Boston.

Like the BA.1 strain, BA.2 has features that help evade immunity from vaccines and most monoclonal antibody therapies, but recent boosts have Improve personal protection Antiviral drugs are still expected to work against this subvariant.

Now, new studies provide some reassurance that BA.2 may overtake its genetically distant cousin, but that will not lead to more hospitalizations and deaths.

“The situation we see on the ground, and this comes from talking to many of our colleagues who are actually doing genome monitoring. BA.2 is a kind of creeping in terms of numbers, It’s not a meteor. The rise we saw at BA.1 “said Angela Rasmussen, a virologist at the University of Saskatchewan, Canada’s Vaccine Infectious Diseases Organization.

This is because in many countries such as the United States, United Kingdom and Denmark, BA.2 hit the speed bumps left behind by BA.1, which was already highly contagious.

“Because it’s just after the first peak of BA.1, many people have been vaccinated or boosted … [or] Now that we have Omicron, all of these people now have relatively high titers of antibodies and will have neutralizing antibodies that prevent infection, “says Rasmussen.

The new study is preprint. That is, it was reviewed by an outside expert and posted to an online library of medical research before it was published in a medical journal.

No increase in hospitalization

first time New research BA.2 came from South Africa, where it grew rapidly, 27% to 86% Number of new Covid-19 infections over the week of February. Researchers have examined more than 95,000 cases associated with a positive Covid-19 test. Of these, approximately equal proportions of people were hospitalized for infections-approximately 3.6% of those who estimated BA.2 infections compared to 3.4% of the symptomatic infections caused by BA.1.

Researchers differ in the risk of hospitalization between those infected with BA.1 and those infected with BA.2 after explaining what may affect the risk of serious illnesses such as old age. Was not seen. Approximately one-quarter of those hospitalized for both BA.1 and BA.2 infections were completely vaccinated.

These findings reflect a Danish inpatient study in which BA.2 is also the leading cause of Covid-19 infection.

Principal Investigator for South African Studies, Dr. Nicole Walter has a hard time saying how South Africa’s experience with this variant will be reflected in other countries, but what he sees from BA.2 after the fourth wave is the second. Say it has a longer tail, not a peak.

“We’ve seen extended waves that are now leveling off at a higher level than we’ve seen in previous wave periods,” Walter wrote to CNN by email. “But this can also be affected by schools opening after the December vacation and relaxation of general restrictions,” wrote Walter, chief medical researcher at the National Institute of Infectious Diseases in Johannesburg. I am.

Cases remain at a high level, mostly due to BA.2, but hospitalizations continue to decline.

What is the risk of reinfection?

The Second new studyRisk of reinfection with BA.2 after recovery from Covid-19 infection caused by other recent variants, including Delta and BA, from the Statens Serum Insects of Denmark (equivalent to the US Centers for Disease Control and Prevention). I looked it up. .1.

The study found that Covid-19-infected individuals recently caused by Omicron or Delta could be re-infected with the newly emerging BA.2 subvariant, but such cases are rare. There are infections that afflict unvaccinated people and are mostly mild.

BA.2 is currently the leading cause of Covid-19 in Denmark. Overtook BA.1 in the second week of January.

To investigate the risk of reinfection, researchers examined more than 140,000 viral genomes sequenced from infection during the Omicron predominance period (late November to mid-February 2022), 20-60. I found people who had a new positive test a day later. The last one.

They found a total of 263 reinfections, 190 of which were caused by the BA.2 variant. In 140 cases, the person was reinfected with BA.2 after infection caused by the delta mutation. There were 47 cases in which people were first infected with BA.1 (the original Omicron variant), followed by the BA.2 subvariant.

Next, researchers conducted a more detailed analysis of the 47 reinfections of BA.2 following BA.1. Most of the re-infected individuals were young, and 30 were under the age of 20. None of the re-infected individuals were over 40 years of age, and almost all 42 of 47 were unvaccinated.

In most cases, reinfection was mild. Twenty-eight had asymptomatic or mild symptoms. Five experienced moderate symptoms that resembled flu-like symptoms. There were no reported hospitalizations or deaths among re-infected individuals.

This study shows that reinfection can occur in people who have recently recovered from BA; 1, but it is very rare, and in all of them it was not serious. ” Says Rasmussen, who reviewed the study but was not involved in the study.

So while re-infection of BA.2 is a risk, it is a small risk compared to the total population, “the recent immune boosts caused by boosters or recent Omicron infections are mostly against it,” he said. ..

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