‘Hypercontagious’ omicron BA.5 variant resistant to prior COVID vaccination, study says

The omicron BA.5 subvariant, which is dominating coronavirus cases reported in the U.S., is much more resistant to mRNA vaccines such as Pfizer and Moderna, according to a recent Columbia University study.

As one of omicron’s newer subvariants, it was described as “hypercontagious” by Dr. Gregory Poland, who leads Mayo Clinic’s Vaccine Research Group.

“Whether you’ve been vaccinated, whether you’ve been previously infected, whether you’ve been previously infected and vaccinated, you have very little protection against BA.5 in terms of getting infected or having mild to moderate infection,” Poland said in a discussion about the subvariant.

The study, published July 5 in the journal Nature, found that BA.5, and another newer omicron subvariant BA.4, were “substantially” more resistant to antibody protection offered by mRNA COVID-19 vaccines compared with earlier variants.

In the U.S., BA.5 makes up more than 65% of reported COVID-19 cases as of July 9 while BA.4 makes up roughly 16%, according to Centers for Disease Control and Prevention data estimates.

Specifically, the study discovered BA.5 and BA.4 are roughly four times more resistant compared to the omicron BA.2 subvariant, which was dubbed “stealth omicron” and dominated reported cases in the spring.

“Our study suggests that as these highly transmissible subvariants continue to expand around the globe, they will lead to more breakthrough infections in people who are vaccinated and boosted with currently available mRNA vaccines,” lead researcher Dr. David D. Ho said in a statement.

Nonetheless, while more vaccinated people may get infected by BA.5, the vaccines “continue to provide good protection against severe disease,” the release noted.

More on the study

Given omicron’s evolution since the first case was recorded in November, “each successive subvariant has seemingly become better and better at human transmission as well as in antibody evasion,” the study said.

Researchers collected blood samples from boosted individuals who had received three doses of an mRNA vaccine and samples from vaccinated individuals (two shots) who had been infected by a coronavirus variant other than omicron, according to the work.

Then, they examined how well the antibodies from the collected blood samples neutralized BA.5, BA.4 as well as BA.2.12.1, the news release said. Omicron BA.2.12.1 is another more recent subvariant that makes up roughly 17% of cases as of July 9, according to the CDC.

Researchers found BA.2.12.1 was “only modestly resistant” (specifically 1.8 times more resistant) to COVID-19 vaccines compared with BA.2, the study said.

Meanwhile, BA.5 and BA.4 “are even better at eluding vaccines” — 4.2-fold more resistant compared to the earlier variants, the news release said.

“Efforts in the United States to develop new vaccine boosters aimed at BA.4/5 may improve protection against infection and severe disease,” Ho said in a statement.

“In the current environment, though, we may need to look toward developing new vaccines and treatments that can anticipate ongoing evolution of the SARS-CoV-2 virus.”

The study was published days after vaccine advisers for the Food and Drug Administration recommended adjusting existing COVID-19 vaccines to target omicron, McClatchy News previously reported. While advisers did not discuss specifically how the vaccines should be altered, it was weighed whether to change them to target BA.5 and BA.4.

“Should we wait for a BA.5 booster?,” Dr. Eric Topol, the founder and director of Scripps Research Translational Institute, wrote in a report about the subvariant, which he called the “worst” version of the virus, in late June.

“By the time a BA.5 vaccine booster is potentially available, who knows what will be the predominant strain?”

In Ho’s statement, he said “the virus is continuing to evolve, as expected, and it is not surprising that these new, more transmissible subvariants are becoming more dominant around the world.”

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