Fragmented COVID-19 microbes in blue and white
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What you need to know

  • BA.5 is the most transmissible COVID-19 strain yet and is better at evading immunity from previous infections.
  • COVID-19 mutations are not becoming more mild. It is possible that a variant will emerge in the future that causes more severe disease.
  • The single most impactful action an individual can take to protect themselves is to stay up to date on their COVID-19 vaccinations.

The COVID-19 virus has gone through several mutations since the beginning of the pandemic. And with each new strain, the virus seems to be getting more transmissible. 

BA.5, the Omicron subvariant now dominant in the country, is likely the most transmissible strain yet. But just days after it made headlines for becoming the dominant strain, attention turned to a new Omicron mutant—BA.2.75—for its worrying spread across the globe.

We asked Dr. Peter Hotez, professor and dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Texas Children’s Hospital Center for Vaccine Development, why variants are becoming more transmissible, what to expect in the near future, and how to stay protected.

Why are variants becoming more transmissible?

The trend throughout the pandemic has been that each new variant or subvariant that emerges is more transmissible than its predecessor. BA.5 spreads faster than BA.2, and BA.2 is more transmissible than BA.1. The same is true for BA.1 over Delta, Delta over Alpha, and Alpha over the original COVID-19 virus.

Hotez explains that this increased transmissibility is tied to the way the virus mutates. So far, research shows that transmissibility has to do with mutations in the spike protein, which is the part of the virus that allows it to penetrate host cells and cause infection. In other words, certain mutations can make the virus better at evading our immune defenses, allowing it to spread faster among humans. But Hotez notes that more research is needed to fully understand the connection.

Are variants becoming less severe?

While it may seem like the COVID-19 virus has evolved to become less severe, this is not true. Each variant and subvariant continues to be capable of causing severe illness and death, especially in unvaccinated individuals and those who are not up to date on their COVID-19 immunizations.

“Even with the high rate of overall vaccination and previous infection in the U.S., 300 to 400 people are still dying per day from COVID-19,” Hotez says. “It’s not 2,000 like it was before, but it’s still a significant cause of death.”

The virus has depended more on increased transmissibility than on increased severity to circulate among humans. But there is no guarantee that future mutations will not create a more severe strain.

What can we expect in the near future?

The U.S. is currently occupied with the rapid spread of BA.5, the most transmissible strain yet. One of the reasons this Omicron subvariant has spread so quickly across the globe is its ability to escape immunity from vaccines and previous COVID-19 infections.

“BA.5 is really very different from Omicron,” Hotez says. “Even though it’s officially listed as a subvariant of Omicron, it’s helpful to think of it as though it has its own Greek letter. With BA.5, past Omicron infection does not seem to protect against reinfection. It has evolved considerably to become more transmissible.”

Now, BA.2.75 is raising alarm bells around the world. It is gaining ground in India and has popped up in several other countries, including the U.S. Scientists are saying that it may be able to evade immunity from vaccines and previous infection, though it’s unclear whether it will outcompete BA.5 and whether it could cause more severe disease.

As for what to expect after BA.5 sweeps through the global population, it’s hard to know.

“I do think we are potentially susceptible to new variants yet unknown, and we could be unlucky enough to get a variant that causes more severe disease,” Hotez says. “This is why there’s still this urgency to vaccinate the world, even though there’s now a lot more complacency.”

How can we protect ourselves from future variants?

The “single most impactful thing” an individual can do to protect themselves is to stay up to date on their COVID-19 vaccinations, Hotez says. The CDC recommends that everyone ages 5 and older get a booster shot. Everyone 50 and older, as well as immunocompromised individuals, should get a second booster.

Variants are becoming more capable of evading our immune defenses, but vaccines continue to prevent severe illness. Boosters maintain, strengthen, and broaden the protection from the primary vaccination series. Yet less than half of the eligible population has received a first booster, and only 28 percent of people ages 50 and older have received a second booster.

Hotez adds that the country is underperforming not only in booster uptake, but also in vaccinating children: Only 36 percent of kids 5 to 11 have started their COVID-19 immunization series, a proportion that is likely in the single digits for kids under 5, he says.

“People are not taking advantage of the technologies we have available,” Hotez says. “Even though everyone [ages 5 and older] can get a booster, most of country is not. The answer is max out your interventions.”