Medical Health Cluster

10 mayo, 2022

Latest COVID Subvariants Create New Waves, Evade Immunity

As COVID-19 cases and hospitalizations begin to increase again in the U.S., public health officials are monitoring several new Omicron subvariants that are contributing to the case numbers.

In some parts of the U.S., a spinoff of the BA.2 subvariant called BA.2.12.1 is the main culprit. In other countries, Omicron subvariants called BA.4 and BA.5 are driving up cases, according to CNN.

All three subvariants appear to be spreading more quickly than BA.2 and creating their own COVID-19 waves.

The U.S. is now reporting an average of more than 62,000 daily cases, according to the data tracker from The New York Times, marking a 50% increase in the past 2 weeks.

Cases are increasing in all but four states and have increased by more than 50%, compared with the previous week, in Georgia, Hawaii, Maine, Mississippi, Montana, Nevada, South Dakota, and Washington, CNN reported. In New York, more than a quarter of the state’s population is in a county with a “high” community level.

About 18,350 COVID-19 patients are hospitalized across the country, according to the latest data from the U.S. Department of Health and Human Services. Hospitalizations have increased about 18% in the past 2 weeks.

Subvariant Growth

BA.2.12.1, which was first tagged by New York health officials in April as a subvariant to watch, is growing about 25% faster than BA.2. It now makes up about 37% of new cases across the U.S., according to the latest CDC date. BA.2 makes up about 62% of new cases, down from 70% the week before.

Health officials are also watching BA.4 and BA.5, which appear to have a growth advantage over BA.2 as well, CNN reported. About 500 BA.4 sequences have been reported in 15 countries and 10 states in the U.S., and nearly 240 BA.5 sequences have been reported in 13 countries and five states, according to the latest data from

BA.4 and BA.5 have contributed to a rise in cases in South Africa during the past 2 weeks, according to CNN. There are also more positive tests and hospitalizations. At the end of April, the two subvariants accounted for about 60% of new cases in the country.

Subvariant Immunity

BA.4 and BA.5 can escape antibodies from previous infections caused by the original Omicron variant, BA.1, which created the COVID-19 surge in December and January. The newer subvariants also appear to escape antibodies in people who have been vaccinated and had breakthrough BA.1 infections.

In a new preprint study, researchers in South Africa tested antibodies in the blood to understand whether they could knock out the BA.4 and BA.5 viruses. People who were unvaccinated but had a recent BA.1 infection were seven times less likely to have their antibodies wipe out BA.4 and BA.5. People who were vaccinated but had a recent BA.1 breakthrough infection were three times less likely to have such antibodies.

By comparison, the World Health Organization uses an 8-fold drop in neutralization as the starting point for requiring an update to seasonal flu vaccines, CNN reported. The researchers concluded that BA.4 and BA.5 have the “potential to result in a new infection wave.” The research lab was the same one that characterized the first Omicron variant.

“Just because you were infected does not mean you have a lot of protection from what’s coming next,” Alex Sigal, PhD, the senior study author and a virologist at the Africa Health Research Institute, told CNN.

In another new preprint study, researchers in China found that BA.4, BA.5, BA.2.12.1, and another subvariant called BA.2.13 all contain mutations at location 452 of their genomes. The area allows the virus to bind to cells better and dodge antibodies. The Delta variant and some others have a mutation at this location. BA.4 and BA.5 also have changes at location 486, which could be related to escaping previous immunity, the researchers said.

Now scientists across the world are trying to understand how these subvariants are mutating so quickly and escaping immunity. Before the COVID-19 pandemic, researchers thought coronaviruses didn’t change much, but now their views have shifted.

“The virus has shown that it mutated slowly, but when it started to pick up good mutations, they just kept coming and coming and coming,” Andy Pekosz, PhD, a virologist and professor of molecular microbiology and immunology at Johns Hopkins University, told CNN.

Subvariant Reinfections

With BA.4 and BA.5 cases increasing in South Africa, scientists are particularly paying attention to reinfections among those who recently had an Omicron case, according to the Los Angeles Times . About 90% of South Africa’s population has immunity to the earlier Omicron variants through a previous infection or vaccination.

So far, only a few dozen sequences of BA.4 and BA.5 have been reported in the U.S. Researchers aren’t sure whether the two subvariants will surge in the U.S. or other countries, but without the reassurance of protection from vaccination or previous infection, surges could be likely.

“It really came out of the blue over the weekend. We were already settling down with BA.2.12.1, then BA.4 and BA.5?” Peter Chin-Hong, MD, an infectious diseases expert at the University of California, San Francisco, told the newspaper.

“It just seems like the latest chapter of a never-ending saga,” he said.

Current data suggests that BA.4 and BA.5 don’t cause more severe disease than other Omicron variants or lead to higher rates of hospitalization or death. But they’re more transmissible and able to get around immunity, Chin-Hong said, and those who are unvaccinated and haven’t had a previous infection are more likely to have a more serious case.

Subvariant Protections

As the Omicron variants create their own pockets of infection in the U.S., public health officials recommend watching local data, the Los Angeles Times reported. When transmission appears to be growing, especially with variants that escape protection from previous infections, people should consider safety measures again, such as wearing masks indoors and in crowded spaces.

The CDC has also recommended that people continue to wear masks on planes, buses, trains, and other public transportation and places where lots of people congregate, according to The Washington Post . Despite last month’s ruling that struck down the federal transportation mask mandate, the CDC stressed this week that masks continue to stop the spread of COVID-19.

“CDC continues to recommend that all people – passengers and workers, alike – properly wear a well-fitting mask or respirator in indoor public transportation conveyances and transportation hubs to provide protection for themselves and other travelers in these high volume, mixed population settings,” Rochelle Walensky, MD, the CDC director, said in a statement.

“It is important for all of us to protect not only ourselves, but also to be considerate of others at increased risk for severe COVID-19 and those who are not yet able to be vaccinated,” she said. “Wearing a mask in indoor public transportation settings will provide protection for the individual and the community.”

Créditos: Comité científico Covid

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