The coronavirus subvariant, known as BA.5, accounted for about 54% of the country’s Covid cases as of Saturday, according to the Centers for Disease Control and Prevention. A similar subtype, BA.4, makes up 17% more.
“They’re taking, so clearly they’re more infectious than the older variants of Omicron,” said David Montefiori, a professor at the Human Vaccine Institute at Duke University Medical Center.
The two subtypes also appear to evade protection from vaccines and previous infections more easily than their predecessors.
Montefiori estimated that the BA.4 and BA.5, omicron variants, are about three times less sensitive to neutralizing antibodies from existing COVID vaccines than the original version of BA.1. Other research suggests that BA.4 and BA.5 are four times more resistant to antibodies from vaccines than BA.2, which replaced the Omicron variant as America’s dominant version of the coronavirus in April.
François Balloux, director of the University College London Genetics Institute, said that most likely there is another reason the subvariants have taken over.
“At this stage, I think all of these types are actually almost equally transmissible, so there’s not a big difference,” he said.
The Food and Drug Administration advisory committee last week recommended revising the booster shots coming from Pfizer and Moderna to directly target BA.4 and BA.5.
Pfizer has told NBC News that it may have an updated vaccine targeting BA.4 and BA.5 ready to be distributed in October.
Most Common Characteristics of BA.4 and BA.5
In the UK, where BA.4 and BA.5 also account for the majority of new COVID cases, last week the most common COVID symptoms were runny nose, sore throat, headache, persistent cough and fatigue. Less than a third of those surveyed reported a fever, according to data from the Zo COVID Symptom Study, which asks people to report their symptoms via a smartphone app.
This is consistent with the traits reported in the UK in spring, when the BA.2 subvariant was dominant.
Balloux said no difference has been observed so far between BA.4 or BA.5 symptoms and the previous subtypes. But people who were infected with the original version of the Omicron version during the winter may be more susceptible to the new subtypes.
“BA.1 and BA.2 are very different,” he said, so cross-protection “isn’t that great.”
Balloux said, however, that “BA.2, BA.4 and B.5 are essentially interchangeable from a neutralizing antibody perspective.” This may mean that people who have had a BA.2 infection now have some protection.
Montefiori said BA.4 and BA.5 also have not been found to cause more severe disease.
“There’s really no clear evidence that they are more or less likely to make people sick and cause serious illness and death,” he said.
Instead, the cases and hospitalizations seen in some places are more likely to result from fading vaccine protection.
“Our immunity is now reduced in people who were boosted half a year or more ago,” Montefiori said.
Will we need more booster shots, and when?
The FDA anticipates that Omicron-specific boosters from Pfizer and Moderna will become available quickly in mid-fall.
“Companies are now working to develop and clinically test a vaccine containing BA.4/BA.5,” Montefiori said.
But experts stressed that there may not be a dramatic difference in protection between Boost and Omicron-specific shots in addition to existing vaccines. Current vaccines still work well to prevent serious illness and death.
“The virus seems to be moving towards more and more avoidance from our vaccines, but vaccines haven’t really found a way to survive to a significant degree,” Montefiori said.
For this reason, he said, people eligible for a second booster — those over 50 or immunocompromised — don’t want to wait.
“If your last boost was over six months ago, you may want to consider re-boosting now with the current vaccine to keep your protection strong,” Montefiori said.
Beyond that, Balloux said, it’s hard to predict whether BA.5 will still be in effect later this year.
“Given the uncertainty, there is no right or wrong,” he said. “There are only trade-offs.”
Europe and South Africa present a preview of the events ahead
Reported Covid case numbers have been relatively flat in the US since May, but case numbers are rising globally.
The World Health Organization said that by the end of June, new weekly cases increased by 32% in Southeast Asia, 33% in Europe and 47% in the Middle East, Central Asia, North Africa and the Horn of Africa region. As of June 19, BA.5 accounted for 43% of omicron cases worldwide, while BA.4 accounted for 12%.
In South Africa this spring there was an increase in cases driven by BA.4 and BA.5, and in the UK there are rising Covid hospitalizations, experts said, adding that trends indicate that the virus may not be able to re-infect people and need vaccines. Getting better at avoiding security.
Nevertheless, the future of the pandemic will depend not only on the properties of the forms, but also on human behavior and how much immunity has built up in the population.
“People really underestimate how much the virus has changed recently,” Balloux said. “There was a massive, massive change between Delta and Omicron, and then, again, quite a massive change between BA.1 and BA.2.”
Not at all with BA.4 and BA.5, he said, although he noted that another major shift in the evolution of the virus could still be coming.