SINGAPORE - Unlike the migrant worker population - where almost 50 per cent of those living in dormitories have tested positive for Covid-19 - the prevalence rate of the virus in the larger community is much smaller, said the Health Ministry's director of medical services Kenneth Mak on Monday (Dec 14).
This lower rate, based on a serology sampling study conducted in the community between September and October, reflects people's adherence to Covid-19 safety measures, he said.
Elaborating on the study, Associate Professor Mak said it found only four out of 1,600 subjects had a positive serology test, which translates to a possible community prevalence rate of 0.25 per cent.
In comparison, about 47 per cent of the 323,000 migrant workers living in dorms have tested positive for Covid-19 as at Sunday (Dec 13), based on polymerase chain reaction (PCR) and serology tests done over the course of the year.
Prof Mak gave the figures at a press conference when asked whether there is a group of Singaporeans who do not need the jab because they may have antibodies from a past infection to shield against reinfection.
Those with a positive serology test would have been infected in the past, at least 10 to 14 days back, while those with a positive PCR test are highly likely to be currently infected with Covid-19.
But, at the same time, the serology results in the community do indicate a higher prevalence rate of Covid-19 infection compared with the prevalence rate derived from positive PCR results, Prof Mak said.
The prevalence of Covid-19 in the community, based on positive PCR results, was around 0.04 per cent, much lower than the 0.25 per cent rate found in the community sampling study.
Similarly, fewer dorm residents tested positive for Covid-19 with the PCR testing than the serology testing. There were 54,505 who tested positive with PCR tests, compared with 98,289 who were positive with serology tests, although they did not have a positive PCR test.
"This is in keeping with our understanding that Covid-19 infection can occur in an asymptomatic fashion among people.
"This is also the reason we need to continue our vigilance and not assume there is no cryptic spread of Covid-19 infection in the community," said Prof Mak.