Two new sub-lineages of the Omicron Covid-19 variant can effectively dodge antibodies from earlier infection to trigger a new wave, scientists have discovered.
Researchers from multiple institutions examined the behaviours of Omicron's BA.4 and BA.5 sub-lineages ― which the World Health Organisation last month added to its monitoring list.
Blood samples were taken from 39 participants who had previously been infected by Omicron. Fifteen were vaccinated — eight with Pfizer's shot; seven with Johnson and Johnson’s — while the other 24 were not.
The study found that the sublineages are less able to thrive in the blood of people vaccinated against the virus.
"The vaccinated group showed about a five-fold higher neutralisation capacity ... and should be better protected," said the study, a pre-print version of which was released at the weekend.
In the unvaccinated samples, there was an almost eight-fold decrease in antibody production when exposed to BA.4 and BA.5, compared with the original BA.1 Omicron lineage. Blood from the vaccinated people showed a three-fold decrease.
South Africa may be entering a fifth Covid wave earlier than expected, officials and scientists said on Friday. They said the sub-variants of Omicron appear to be driving infection numbers upwards.
Only about 30 per cent of South Africa's population of 60 million is fully vaccinated.
"Based on neutralisation escape, BA.4 and BA.5 have potential to result in a new infection wave," the study said.