BA.5 What Subvariance Could Mean for the United States

The most transmissible variant of the coronavirus is still threatening a new wave of infections in the United States, even among people who have recently recovered from the virus.

Known as the Omicron subvariant BA.5 is now dominantThat, along with another subvariant, BA.4, is driving the rise in cases and hospitalizations, according to federal estimates released Tuesday.

Although the popularity of home testing means that the true infection rate of reported cases is significantly lower, the proportion of positive tests is rising and is now higher than in most waves of the pandemic. According to the CDC, the risk of Covid-19 is increasing in most parts of the country.

“I think there’s an underestimation of what this will do to the country, and it’s already having an impact,” said Eric Topol, a professor of molecular medicine at Scripps Research. written about the subvariant.

BA.5 and BA.4, both subvariants of the Omicron variant that swept the world during the winter, are still the most adept versions of the virus at warding off previous infections and vaccines. Both variants have mutations in their spike proteins that are different enough from earlier versions of the virus that they can evade some antibodies.

Waves of infection—and the subsequent immunity that comes with them—vary and compare imperfectly across countries. Vaccination rates also vary. But where BA.4 and BA.5 have been dominant for weeks or months, the subvariants have caused an increase in cases and hospitalizations, despite some population immunity from previous waves.

The CDC says there is no evidence yet that BA.4 or BA.5 is more severe than other Omicron subvariants, but as more people become infected, the number of people hospitalized for the virus could increase.

Previous infection with another form of the Omicron variant confers some degree of immunity, Dr. And that may explain why things haven’t taken off sharply in the U.S., Topol said. “But it’s not what we hoped for,” he said. Omicron subvariants represent divergence from previous waves of virus when previous infection is more likely to protect against reinfection.

In Portugal, where vaccination rates are higher than in the United States, cases have risen sharply since BA.5 became dominant in May and hospitalizations neared the pre-Omicron peak.

Before BA.4 and BA.5 prevailed in South Africa in April, studies show that 98 percent of the population had some antibodies from vaccination or previous infection or both.

Even with those protective antibodies, many people in the country are still infected with BA.4 and BA.5, and the subvariants have caused a slight increase in cases, hospitalizations, and deaths.

Newly emerging areas may not be protected from significant spring waves of the virus. Large outbreaks of a different Omicron subvariant, BA.2, have occurred in several European countries, leading to new waves of hospitalizations and deaths, which peaked in April. However, cases are increasing again as BA.5 becomes dominant in those countries.

Experts say it’s too early to fully predict what the latest subvariants might bring to the United States, with an even newer wave of viruses in May and June, driven by both BA.2 and another subvariant called BA.2.12.1. As in the United States, high proportions of recent infections from BA.2.12.1 were unusual among countries currently experiencing waves of BA.4 and BA.5 infections.

The United States has a lower vaccination rate than many of these countries, and the share of seniors who have received one or both booster shots is much lower.

“There is a wave, there is no doubt about it,” said Dr. Topol said. “What worries me is the length of it.”

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