Thanks to mutations that greatly enhance its transmissibility and ability to evade immunity, the omicron subvariant BA.5 is currently driving a new surge of Covid-19 cases and hospitalizations across the United States. To combat the surge, health officials are encouraging "established countermeasures," such as booster shots, antiviral treatments, and indoor masking.

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BA.5 continues to surge in the US

According to CDC data, BA.5 is the dominant coronavirus variant in the United States, currently responsible for 77.9% of reported Covid-19 cases. Infections from BA.5 have been on the rise, and the average number of reported daily new cases now tops 125,000—although experts say the true number is likely much higher considering reports don't include at-home tests.

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Federal data shows that hospitalizations are also on the rise. Since early May, Covid-19 hospitalizations nationwide have doubled, and the United States is averaging more than 6,000 new hospital admissions a day.

"We're in a surge," said Eric Topol, a cardiologist and director of the Scripps Research Translational Institute. "It won't be as bad as what we went through in January [during the first omicron surge]. But it isn't good. And we basically have let our guard down."

Evidence suggests BA.5 has several mutations that increase its transmissibility and improve its ability to evade immunity. For example, a recent study in the New England Journal of Medicine found that existing immunity is much less protective against BA.5 than against previous omicron subvariants.

"Let me make a clear, clear point here that's a little tough to hear: Whether you've been vaccinated, whether you've been previously infected, whether you've been previously infected and vaccinated, you have very little protection against BA.5 in terms of getting infected or having mild to moderate infection," said Gregory Poland, head of the Mayo Clinic's Vaccine Research Group. "You have good protection against dying, being hospitalized or ending up on a ventilator."

How health officials are responding to the surge

Earlier this month, the Biden administration announced new guidance to combat the BA.5 surge. Federal health officials strongly urged people, especially those who are age 50 or older and have an increased risk for severe illness, to get a Covid-19 booster dose.

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Currently, people ages five and older are eligible for a booster dose five months after their initial vaccine series. So far, only individuals ages 50 and older are eligible for a second booster, but federal officials are considering expanding eligibility to all adults.

"If you've not gotten a vaccine shot this year, go get one now," said Ashish Jha, the White House Covid-19 response coordinator. "It could save your life."

Health officials have also encouraged people to use antiviral treatments, test themselves regularly, and wear masks in crowded indoor spaces.

BA.5 "doesn't really shake up any of our established countermeasures," said Anne Hahn, an immunologist at Yale Medical School. According to Vox, masking and vaccines are still effective at preventing severe illness from BA.5.

So far this year, various omicron subvariants have been the dominant versions of the coronavirus, but there is still a possibility that completely new variants will emerge in the future.

"While things do seem to be at least somewhat different with omicron, in that [it's] given rise to so many successful subvariants, I don't think we can rule out that there may be another variant appearing unexpectedly," said Emma Hodcroft, a molecular epidemiologist at the University of Bern.

"What this is telling us: we need to remain vigilant," said Daniel Barouch, director of the Center for Virology and Vaccine Research at the Beth Israel Deaconess Medical Center.

"Everybody's hoping to get a degree of what they call endemicity — living with the virus at a level that does not disrupt society," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. "That's where I think we're going. I don't believe we're going to eradicate this." (Ioanes, Vox, 7/24; Irfan, Vox, 7/17; Landman, Vox, 7/15; Archie, NPR, 7/15; Mueller, The Hill, 7/17)