Singapore detects three COVID-19 cases infected with new BA.4 and BA.5 Omicron subvariants

“We will step up local surveillance efforts and continue monitoring the spread of BA.4 and BA.5 in Singapore. While our society is now more resilient against the virus, everyone should continue to play their part and remain vigilant to mitigate the spread of COVID-19,” said MOH.

“In particular, persons vulnerable to complications of COVID-19, such as unvaccinated persons, persons above the age of 60, and persons with chronic diseases, should ensure they are up to date with their recommended boosters and exercise caution in settings with many potential contacts.”

Both BA.4 and BA.5 contain mutations in the spike protein which appear to confer greater immune escape properties and higher transmissibility compared to the BA.1 and BA.2 causing the Omicron wave earlier this year. 

However, emerging real-world evidence from other countries supports that BA.4 and BA.5 infections will likely give rise to similar clinical outcomes, compared to previous Omicron lineages. 

According to the WHO, at least 1,000 cases of BA.4 and BA.5 have been reported in at least 16 countries as of May 11.

SUBVARIANTS DODGE ANTIBODIES FROM INFECTION

South Africa is experiencing a surge of new COVID-19 cases driven by these two subvariants, with the country seeing increasing numbers of new cases and somewhat higher hospitalisations.

However, there have been no increases in severe cases and deaths.

Earlier this month, South African scientists found that BA.4 and BA.5 can dodge antibodies from earlier infection well, but are far less able to thrive in the blood of people vaccinated against COVID-19, according to a Reuters report.

Tests involving blood samples from unvaccinated participants previously infected by Omicron showed that antibody production was decreased almost eightfold when exposed to BA.4 and BA.5, compared with the original BA.1 Omicron lineage. Blood from vaccinated people showed a threefold decrease.