Three hands holding up vaccine vials.
Illustration: PGN

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What you need to know

  • BA.5 is now the dominant variant in the U.S.
  • The FDA advised vaccine manufacturers to develop Omicron-specific vaccines for the fall.
  • Experts recommend that everyone get their boosters now rather than wait for the updated vaccines.

Daily COVID-19 cases in the U.S. have remained relatively stable for the past month, but case counts are not low. The country’s daily average for reported cases has hovered at around 100,000 for weeks now, and the true number is likely higher due to the prevalence of at-home tests that go unreported.

This high plateau can at least partially be attributed to the rapid spread of BA.4 and BA.5, two Omicron subvariants that now make up 70 percent of the country’s circulating COVID-19 viruses.

How transmissible are BA.4 and BA.5? 

Based on what we know so far, BA.4 and BA.5 are the most transmissible COVID-19 variants yet. This increased transmissibility has been a trend throughout the pandemic, with newer variants having a growth advantage over their predecessors. BA.4 and BA.5 are about 1.4 times more transmissible than their predecessor BA.2, which has a similar growth advantage over BA.1.

The two variants are also better at evading immunity, which means that people who are vaccinated or were infected with a previous variant are more likely to get reinfected when it comes to BA.4 and BA.5.

How can I stay protected against BA.4 and BA.5?

We have several tools at our disposal to stay protected against these two new variants, including vaccines, masks, tests, and treatments. 

Staying up to date on your COVID-19 vaccinations is the best way to prevent severe illness from the virus, regardless of the strain. Our current vaccines no longer offer much protection against infection from these more immune-evasive strains, but boosters continue to decrease the risk of hospitalization and death by both strengthening and broadening our immune response. 

Besides boosters, high-quality masks can be particularly useful at preventing infection; frequent testing can help limit the spread of the virus; and treatments work to prevent the worst outcomes of infection.

In a few months, we may also have vaccines that specifically target BA.4 and BA.5. The FDA advised vaccine manufacturers last week to develop Omicron-specific vaccines for the fall in anticipation of another COVID-19 wave. 

When will these updated vaccines become available?

Both Pfizer and Moderna have already started developing and testing Omicron-specific vaccines and have said that they could deliver the modified doses in October at the earliest. But Dr. Celine Gounder, clinical associate professor of medicine and infectious diseases at New York University’s Grossman School of Medicine, says this timeline could change. 

“There are always unpredictable factors, like supply chain issues or problems at the manufacturing plant, that could delay vaccine manufacturing,” she says.

Should I wait for the updated vaccines to get a booster?

Gounder does not recommend waiting to get a booster until the updated vaccines are available, since it’s still unclear when they will be ready, and COVID-19 transmission levels are already high across the country. 

“People should aim to stay up to date with the vaccines in the present and worry about updated boosters when they come along,” Gounder says.

Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health, agrees that people should get boosted as soon as they become eligible. He notes that despite the ability of BA.4 and BA.5 to evade immunity, our current vaccines continue to “protect against what matters—severe disease, hospitalization, and death.”

This means that everyone ages 5 and older should get their first booster shot, and everyone 50 and older, as well as immunocompromised individuals, should get their second booster.

What if a new variant arises in the fall? Will the updated vaccines still be effective?

It’s difficult to predict what variant will be of highest concern by fall, but scientists and regulatory agencies believe updated vaccines targeting BA.4 and BA.5 will offer the best protection based on current information.

“We don’t know if [BA.4 and BA.5] will remain the dominant strains over fall and winter—we don’t really have the crystal ball to make that prediction,” Gounder says. “The best we can say right now is that, if a new variant emerges, it will likely be a descendant of Omicron or maybe a descendent of Delta.”

In order to cover these two bases, vaccine manufacturers are working toward a vaccine that includes the BA.4 and BA.5 components in addition to the current vaccine formula. The hope is that the current vaccine will be effective against descendants of Delta, while the BA.4 and BA.5 addition will protect against strains that emerge from the Omicron lineage. 

Even if the updated vaccine ends up being a mismatch for variants that become prevalent this fall and winter, we won’t necessarily be worse off, Adalja says.

“Updating the vaccine is more about improving protection against infection,” he explains. “If [the dominant variant] changes, we would be in no worse situation than we are in now. This means that, yes, infections will occur in vaccinated people, but they will be much less severe.”