SINGAPORE - A recent survey commissioned by The Straits Times of 1,000 people aged 16 and above here found that about eight in 10 would say "yes" to getting a Covid-19 vaccination, with more than half in this group willing to get it the moment it is available.

About 18 per cent of respondents, however, would not want to receive a Covid-19 vaccine, regardless of whether one was available today or in six to 12 months, although about half were willing to consider having one eventually.

With Covid-19 vaccinations under way in some countries and expected to start in Singapore soon, the question now is how open people are to the shots.

The online poll, conducted by online market research firm Milieu Insight from Dec 3 to 7, found that 48 per cent will get a vaccine when it is available, 34 per cent will wait six to 12 months, and 9 per cent will consider having one eventually.

The remaining 9 per cent said they will not get a Covid-19 jab at all.

The poll suggests that Singaporeans are far more open to Covid-19 vaccines than others in places like the United States, where recent data from the Pew Research Centre showed 60 per cent of people would definitely or probably get a vaccine for the coronavirus.

Still, this is up from 51 per cent in September, when people in the US worried that the Trump administration might rush through a vaccine before it was properly tested.

Almost a year on since the novel coronavirus struck, five Covid-19 vaccines have applied for emergency use authorisation.

Just this week, the United Kingdom began giving healthcare workers and elderly people the Pfizer-BioNTech vaccine (code-named BNT162b2), making it the first country in the world to authorise the shot for emergency use.

The vaccine has also since been approved for use in Canada, Bahrain and Saudi Arabia.

Some of the initial wariness about whether Covid-19 shots would be safe and effective might have come from the language used about their development. This included terms such as "warp speed" and "race", which made it sound like they were being rushed or safety guidelines were ignored, said Professor Paul Offit, director of the Vaccine Education Centre at the Children's Hospital of Philadelphia and a US Food and Drug Administration (FDA) vaccine advisory committee member.

Similarly, the ST poll found that the top concern among those hesitant about having a Covid-19 vaccine was safety, including possible side effects. Others wanted to be sure that it is effective.

Ms V. Lee, 44, who holds a managerial post and who did not participate in the poll, said: "I will let others be the guinea pigs, and wait six months to one year."

She said she was wary, particularly after reading that two people in the UK had allergic reactions to the Pfizer-BioNTech vaccine, although the two have a history of serious allergies. The British health authorities have advised those with a history of anaphylaxis to medicine or food against having the jab.

Side effects, such as swelling at the injection site or low-grade fever, can occur with any vaccines.

In the Pfizer-BioNTech trial, which had more than 40,000 volunteers, the most common side effect was pain at the injection site, reported by 84 per cent of the participants. This was followed by fatigue (63 per cent), headache (55 per cent), muscle pain (38 per cent), chills (32 per cent), and others.

Experts say the side effects are temporary and show that the body is building immunity against Covid-19.

On Thursday (Dec 10), Professor Tan Chorh Chuan, chief health scientist at Singapore's Health Ministry, told reporters that regulators typically look at two aspects of side effects - the immediate and short-lived, and the serious.

"Even after vaccination starts, as in the UK, surveillance for side effects will continue quite intensively," said Prof Tan, who is part of a 14-member vaccine advisory committee here.

Associate Professor Hsu Li Yang, vice-dean of global health and leader of the infectious diseases programme at NUS' Saw Swee Hock School of Public Health, said the common and even rarer adverse events associated with immediate and early stage vaccine use would virtually all have been experienced by the participants in the Phase 3 trials, and reported.

"Delayed adverse events from vaccination are rare and difficult to prove, and are often associations due to chance rather than directly due to the vaccination per se," he said.

"Unfortunately, they are also difficult to disprove, as can be seen from the long-running MMR-autism saga."

Concerns about a possible link between the MMR vaccine, which protects against measles, mumps and rubella, and autism were raised in the late 1990s, although it was later disproved in multiple rigorous studies.

Prof Tan said Covid-19 vaccines are new, and understandably, people have concerns.

"On the other hand, we have an established process for reviewing new drugs, new vaccines. And the process has to be done stringently and thoroughly, to make sure that the things that are approved are safe and efficacious," he said.

Vaccine advisers to the US FDA voted on Thursday to recommend that the agency grant emergency use authorisation to the Pfizer-BioNTech Covid-19 vaccine, which has an efficacy rate of 95 per cent. They will meet again on Dec 17 to discuss the Moderna vaccine (94.1 per cent efficacy), which is also pending authorisation by the European Medicines Agency.

Although the full results of the completed Phase 3 trials are not publicly available yet, they are being assessed by highly reputable regulatory agencies that will ensure that safety and efficacy criteria are met, said Prof Hsu.

Approval would indicate that a vaccine was administered safely to tens of thousands of people without any serious adverse effects. However, in some places, vaccines are already being rolled out without having tested a lot of people.

Russia's Sputnik V and China's Sinopharm and Sinovac Biotech vaccines have received emergency use authorisation in their respective countries despite not having completed Phase 3 trials, and are being rolled out, noted Prof Hsu.

There are about 45 other Covid-19 vaccine candidates currently undergoing human trials, including one developed by Oxford University and AstraZeneca.

Prof Tan said Singapore will not rely on just one vaccine, as production would not be sufficient.

And while it is rational from the individual perspective to wait up to a year before taking a vaccine, this choice affects society at large.

"If the majority of people do this, then we end up with a tragedy of the commons from the perspective of the Covid-19 vaccination programme, because high vaccination rates are necessary for herd immunity," said Prof Hsu.

At the moment, the long-term efficacy of the Covid-19 vaccine frontrunners is unknown, but this is an issue that will only be clearer with time, said Prof Hsu.

"I think it is important for those who are hesitant to find out more about the vaccines via reliable sources of information," he said.

"They should also attempt to understand the specific issues that result in vaccine hesitancy and refusal, which may be different between persons, and make objective attempts to address these issues, including speaking with healthcare professionals."

Vaccines are not entirely risk-free but neither is the choice of not getting one in this pandemic.

The risk of becoming severely affected by Covid-19 is much higher than with a vaccine, experts noted.