Omicron subvariants can evade immunity from past infection, study says

Driving the news: The World Health Organization said last month that it was tracking cases of the two Omicron subvariants, BA.4 and BA.5, Reuters reported.

• The BA.4 subvariant has been driving a recent spike in infections in South Africa, though hospitalizations have risen only slightly and deaths have remained stable, AP reported Friday.
• Experts believe BA.4 may be more transmissible than the original Omicron variant or earlier subvariants, such as BA.2, per AP.

State of play: The study analyzed the blood samples of 39 people who'd been infected with the Omicron variant last year, 15 of whom were vaccinated and 24 of whom were not, per Reuters.

• The study, led by the Africa Health Research Institute in South Africa, found that the blood samples of the vaccinated people showed a threefold drop in antibody production when tested against BA.4 and Ba.5, Bloomberg reported.
• However, unvaccinated subjects who'd previously been infected with Omicron saw an eightfold drop in neutralizing antibody production when confronted with the new subvariants.

• The study has not been peer-reviewed, per Bloomberg.

What they're saying: “The low absolute neutralization levels for BA.4 and BA.5, particularly in the unvaccinated group, are unlikely to protect well against symptomatic infection,” the study noted, per Bloomberg.

• “This may indicate that, based on neutralization escape, BA.4 and BA.5 have potential to result in a new infection wave.”
• "The vaccinated group showed about a 5-fold higher neutralisation capacity ... and should be better protected," it added, per Reuters.