Sinovac's Covid-19 vaccine, under growing scrutiny over its effectiveness, has found a small but determined group of takers in Singapore - even though the country does not count them as being vaccinated in its official tally.

Singapore provides the more effective mRNA shots from Pfizer-BioNTech and Moderna free under its national vaccination programme but thousands have chosen to pay as much as S$25 for Sinovac's CoronaVac.

"I personally don't trust (mRNA) results, compared with something that is traditional, which has been used for over 100 years," said Tan Bin Seng, a retired Singaporean doctor, referring to inactivated-virus vaccines.

Some see no downside to...