SINGAPORE - Living with a younger sister who has decided against vaccination has been frustrating for Mr Lim King Joo, 70.

Mr Lim, who is waiting to receive his booster shot next month, having completed the first two rounds in early May, said his 65-year-old sister has not received a single dose of the vaccine.

"She refuses to go and I can't convince her. She says she's afraid of the side effects," he said, adding that his three other siblings have also tried talking to her but to no avail.

Mr Lim, who is a divorcee, shares a flat in Bedok Reservoir with his unmarried sister.

The former financial consultant shared that these disagreements have resulted in some friction within the family, but his primary concern is his sister's health.

"I'm also concerned if she heads out, because she is not protected and she can spread it to me. She has other health issues such as high blood pressure and high cholesterol, which she refuses medication for," said Mr Lim.

Booster shots were rolled out for those aged 50 and above a week ago, but some seniors have decided against taking the third dose of the vaccine.

Retired maintenance officer Jeswant Singh, 68, said he has heard of people getting "all kinds of problems" following the booster shot.

He said: "A lot of old people come and tell me after their third vaccination they have headaches.

"I am comfortable with two (vaccinations). I see no difference. The Government said that the vaccine is just a precaution and so I got the first two."

Mr Singh was one of two people The Straits Times spoke to who said they would not take the booster. Sitting outside a coffee shop in Beach Road, he said he was not concerned about getting the virus, adding that he had not heard of cases involving the elderly in the area.

Mr Lim said some seniors may be reluctant to get the vaccine due to misinformation on social media. He added: "Some of my friends don't trust the vaccine because they think there hasn't been enough research. They think the whole process has been a bit (rushed) and the manufacturers may be keeping some things to themselves."

Mr Singh said he relies on WhatsApp chat groups for news, with friends sending links that have been forwarded multiple times.

Smoking his pipe as he sat in front of a shophouse near the Sultan Mosque, Mr Nordin, 61, also said he would not get the booster shot.

"I don't go to crowded places or mix around with other people. I just need to find a place to sit down, have my coffee, and smoke my pipe. And if God tells me I'm okay, then I'll be okay," he added.