SINGAPORE - In late July, logistics driver R, 30, found out he was infected with Covid-19.

The Singaporean was staying at Institution S2 Selarang Park Complex - which houses those serving the tail end of their sentences in community-based programmes - where a cluster had formed.

Fully vaccinated since late May, R - who did not wish to be named or disclose his offence - thought his Covid-19 episode would be like a usual bout of flu.

It turned out that his illness was mild enough for him to avoid being hospitalised, but the symptoms were worse than expected.

"I got some breathing difficulty... had blocked nose, cough and my body was aching," he said.

"Usually, for normal flu, I have a nasal spray that can relieve my blocked nose, but for this Covid-19, I couldn't relieve (my blocked nose) with the spray."

Those at the prison facility he is in were swabbed for Covid-19 and promptly isolated soon after it became known that someone had tested positive for the disease in late July.

He was first taken to Amara Hotel in Tanjong Pagar. The next morning, on July 30, a call came, informing him that he had tested positive for Covid-19.

That day, he was transported to community care facility D'Resort in Pasir Ris, where Covid-19 patients with mild or no symptoms recover in isolation. He said at least one older bunk mate was taken to a hospital.

The Ministry of Health (MOH) announced the cluster of six cases at the prison facility on July 31.

By Aug 1, MOH said that about 350 of those serving the tail end of their sentences as well as officers at the work release centre in Selarang Park Complex had tested negative for Covid-19.

For R, not long after arriving at D'Resort, he realised he had lost his sense of smell and taste.

"It was scary. You try to imagine that you can't smell your shower soap. I think I am still recovering," he said.

"My sense of taste came back on Aug 12, but I was unable to smell anything."

Breakthrough infections occur when someone who is fully vaccinated and protected - this kicks in 14 days after the final vaccine dose - catches Covid-19. Vaccination helps to reduce the severity of the illness.

Dr Louisa Sun, a consultant at Alexandra Hospital's infectious diseases and chronic programme, said: "Those who have symptoms have the usual fever, dry cough, sore throat... but these are usually milder than the symptoms of those who are unvaccinated."

A month-long pilot programme starts this week where eligible, fully vaccinated people with mild or no symptoms can self-isolate at home, with about 50 to 60 people expected to be on it.

Health Minister Ong Ye Kung had said earlier this month that some people would be allowed to recover at home, as more than 98 per cent of infected people who are fully vaccinated show mild or no symptoms.

R was discharged on Aug 12 after testing negative for Covid-19.

However, at the prison facility that night, he felt weak. "I had difficulty breathing and they called the ambulance. I went to Tan Tock Seng Hospital."

He was discharged after one night at the hospital.