What to Know About BA.5, the Subvariant One Expert Calls the “Worst” Yet

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And a look at the new boosters being developed to target this fast-spreading strain.

The latest Omicron offshoot has quickly become the dominant strain in the U.S. Here’s what you need to know about BA.5 and your risk for reinfection.

How common is the new Omicron subvariant, BA.5?

The subvariant now accounts for 54 percent of cases in the U.S., per the Centers for Disease Control and Prevention. The strain is considered the most contagious yet and is fueling a new wave of infections and hospitalizations. Official data place the number of daily cases at about 100,000, but experts warn that the real figure is likely much higher because so many Americans are now testing at home or not testing at all, the New York Times reports.

What makes BA.5 so contagious?  

BA.5 — and a very similar subvariant, BA.4 — carry mutations in their spike proteins that allow them to easily evade immunity from a prior infection or vaccination. That’s led to some people becoming reinfected just weeks apart, first with an earlier Omicron strain like BA.2 and later with BA.4 or BA.5. Because of this, Eric Topol, a professor of molecular biology at Scripps Research who has closely tracked the pandemic, calls BA.5 “the worst version of the virus that we’ve seen.”

What are the symptoms of Covid subvariant BA.5?

The most common symptoms appear to be runny nose, sore throat, fatigue, headaches, and muscle aches. Unlike previous versions of the virus, people with BA.5 are less likely to lose their senses of taste and smell or experience shortness of breath, an infectious disease specialist tells the New York Times. The subvariant also doesn’t seem to cause more severe illness than earlier subvariants. 

Should you get a booster shot now or wait for the fall?

The FDA is asking vaccine makers to create new versions of their boosters built specifically to protect against BA.4 and BA.5. Many scientists believe updated boosters are critical, but Pfizer and Moderna have said they could deliver those shots no earlier than October, the Times reports.

Given how rapidly this virus mutates, it’s unclear whether BA.4 and BA.5 will remain the dominant strains once the new formulations of the boosters are available. “I worry that by the time we have a vaccine for BA.5 we’ll have a BA.6 or a BA.7. This virus keeps outsmarting us,” Ziyad Al-Aly, an epidemiologist at Washington University in St. Louis, tells the Washington Post.

Still, virologists say the subvariant vaccine would provide the strongest protection against current strains of the virus and broad defense against whatever form the virus takes next. That’s why Johns Hopkins epidemiology professor Kawsar Talaat recommends that if you’re under 50 and not at an elevated risk to hold out for the fall upgrade. But if you’re over 50 or immunocompromised he tells National Geographic: “Don’t wait for a better vaccine, because you leave yourself vulnerable.”