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

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

People wearing protective face masks in the Central Business District in Singapore on Mar 25, 2022. (Photo: CNA/Gaya Chandramohan)

SINGAPORE: Three community cases with new Omicron subvariants have been detected in Singapore, said the Ministry of Health (MOH) on Sunday (May 15).

Two cases were infected with the BA.4 variant and one local case was infected with the BA.5 variant.

"These are the first community cases confirmed to be infected with the BA.4 and BA.5 variants," said the ministry, which detected the cases as part of its active surveillance of the COVID-19 situation.

The European Centre for Disease Prevention and Control recently classified them as variants of concern. The World Health Organization added BA.4 and BA.5 to its list for monitoring earlier in April.

Both lineages were first reported by South Africa in early 2022 and have since become the dominant variants there. 

The cases in Singapore were detected via further testing of polymerase chain reaction (PCR) positive samples and confirmed through whole genome sequencing (WGS), said MOH.

All cases were either asymptomatic or had mild symptoms such as fever, cough, runny nose and sore throat, and did not require hospitalisation. They are fully vaccinated and had earlier received their booster dose.

The three cases had self-isolated upon testing positive for COVID-19 and did not have any reported exposure to vulnerable settings, the ministry added.

"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.


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.

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Source: CNA/ic(ta)


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