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What you need to know

  • The Omicron subvariants BA.2 and BA.2.12.1 make up nearly all COVID-19 cases in the country.
  • Both BA.4 and BA.5 are now in the U.S. and show signs of being able to evade immunity.
  • Regardless of the variant and its ability to evade immunity, vaccines remain one of our most effective tools, especially for protecting against severe illness.

After experiencing a steep decline from the Omicron surge, the U.S. is now seeing its case counts rise again. The BA.2 Omicron subvariant and its spinoff, BA.2.12.1, seem to be behind the increase. These are not the only offshoots scientists are keeping their eyes on, though—two other Omicron subvariants, named BA.4 and BA.5, have been driving surges abroad.

What do we know about the Omicron subvariants BA.2 and BA.2.12.1?

The highly transmissible BA.2 subvariant and its descendant BA.2.12.1 make up nearly all COVID-19 cases in the country now. BA.2 is more transmissible than Omicron, and BA.2.12.1 has a growth advantage over BA.2. It spreads about 25 percent faster than its parent virus BA.2.

The good news is that vaccines continue to protect against BA.2. In addition, people who were previously infected by Omicron are unlikely to get reinfected by BA.2. The case for BA.2.12.1 is less certain. Some preliminary data has shown that this subvariant has the ability to evade immunity, particularly immunity from prior Omicron infections. But even so, neither of these variants appears to be more severe than the original Omicron strain.

What do we know about BA.4 and BA.5?

BA.4 and BA.5 are the Omicron subvariants behind the concerning recent case surge in South Africa. The subvariants are spreading in South Africa despite the fact that nearly the entire country’s population is protected by some kind of immunity, either from vaccination or previous infection.

This suggests that BA.4 and BA.5 are not only more transmissible than previous Omicron subvariants, but also have the ability to evade immunity. Both BA.4 and BA.5 are now in the U.S., but their prevalence in the country is still unclear.

How can we protect ourselves from another surge?

Regardless of the variant and its ability to evade immunity, vaccines remain one of our most effective tools. Vaccines trigger a range of immune system mechanisms, and it’s unlikely that a variant is completely unaffected by all of them. Boosters are especially important as they strengthen and build upon the immune system’s response to the initial vaccine.

Besides staying up to date with COVID-19 vaccinations, it’s smart to monitor your community’s risk level with the CDC’s COVID-19 by County tool. The agency updates its data weekly along with guidance on masks, rapid testing, ventilation of spaces, vaccines, treatment, and more.