When unvaccinated samples were exposed to BA.4 and BA.5, antibody production was nearly eightfold lower than when they were exposed to the original BA.1 Omicron lineage. The vaccinated people's blood indicated a threefold reduction.

Officials and scientists in South Africa said on Friday that the country may be entering a fifth COVID wave sooner than predicted, blaming a continuous surge in infections that appears to be driven by the BA.4 and BA.5 Omicron sub-variants.

Only approximately a third of South Africa's 60 million people are properly immunized.

"BA.4 and BA.5 have the ability to trigger a fresh infection wave based on neutralisation escape," the study concluded.