Vaccination rate of 80 per cent needed to build up herd immunity: Prof Tan Chorh Chuan

Singapore’s Chief Health Scientist Professor Tan Chorh Chuan has a message for everyone: Go and get vaccinated against COVID-19.

His target: At least 80 per cent of the population should get the shot. The greater the number of people who are vaccinated, the tougher it will be for the virus to spread – and the safer our society will be.

This will build up herd immunity – where the population is protected from a virus if a threshold of vaccination is reached – and chances of a sizeable outbreak will be significantly reduced, noted Prof Tan, who is also Chairman of the Committee of Government Scientific Advisors.

In an interview with Inconvenient Questions (IQ), the former President of NUS added: “We’re not going to be able to eradicate this virus – it’s going to be with us for a long time. But if the impact of infection is markedly reduced, then it will not be as severe as it is now.”

Yet, even as the world – and Singapore – now has viable vaccines to fight the pandemic, many are not rushing to get the shots due to concerns over safety and side effects. Scientists and regulators worldwide have provided assurance that these concerns are unfounded, and that the vaccines are safe.

Allaying fears about the vaccines

Prof Tan sought to assure people about the vaccines, especially those who are worried about how fast they were developed.

Typically, trials for new drugs and vaccines can take up to 10 years. But the Pfizer-BioNTech vaccine secured by Singapore, for instance, was developed and approved within a year.

The vaccine’s rapid creation can be attributed to two things. With prior studies done on other coronaviruses such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS), development of a related vaccine was accelerated.

Furthermore, the Pfizer-BioNTech vaccine trial involved more than 44,000 people – far more than the usual 3,000 to 4,000 participants. With the large sample size, its effectiveness could be better tested under the same rigours, said Prof Tan.

To date, this vaccine has proven efficacy and safety. This means that there will be a 95 per cent chance of developing immunity and an extremely low possibility of serious side effects.

“What we have to do is to continually share, in a transparent manner, data which are science-based to persuade these individuals that the vaccine is indeed safe and efficacious,” said Prof Tan.

Despite what science says, he recognised that gaining the public’s trust is a challenge, given the large amount of information – and disinformation – floating around.

It is an ongoing effort that requires constant engagement between health officials and the public. At the same time, showing Singaporeans that the vaccine is safe – by having political leaders take the vaccine early – will also inspire trust.

There will, however, always be some resistance against the vaccines as Singaporeans feel safe with low community infections rates. But he cautioned that this false sense of security brings great risks.

“The nature of human interaction is so complex that the virus will eventually find a way to create new ways of infection,” he said. “There will be an ever-present threat of future outbreaks, and if we’re unlucky, it will become big.” 

Immunity for all

Individual actions have a big part to play in overcoming the pandemic.

“Each individual’s decision is going to have an impact on how society actually moves forward in our battle against COVID-19,” said Mr Viswa Sadasivan, Chief Executive Officer of Strategic Moves and a former Nominated Member of Parliament, who conducted the interview.

The only way forward is to achieve herd immunity. “With no immunity against this infection, whatever we do now (is just trying) to stave off being exposed, but the fact is most of us remain susceptible,” said Prof Tan.

What will work is a sequential vaccination. For example, administering the vaccine to healthcare workers first would make them less likely to be infected, which prevents the healthcare system from becoming overwhelmed.

Once they and vulnerable groups such as the elderly have been inoculated, the next step is to vaccinate the majority of the population to keep Singapore safe.

This will also help those who may not be suitable for vaccination, as herd immunity offers them an indirect form of protection from COVID-19.

“In that way, we won’t just be protecting ourselves,” he noted. “We will be protecting the wider community, including our loved ones and those who are not able or suitable to have the vaccine.”

As a country, Singapore is also doing its part to stem the outbreak by joining COVAX, a multilateral vaccine initiative co-led by public-private health alliance Gavi; the Coalition for Epidemic Preparedness Innovations; and the World Health Organisation.

It aims to deliver equitable access to COVID-19 vaccines worldwide, which will hopefully lead to the re-opening of borders gradually. This is vital for Singapore, a nation that depends on open economies and open borders to thrive.

“The vaccine will let us open up safely because the alternative is to seal ourselves off for a long time, which is not going to be feasible for Singapore,” said Prof Tan.

IQ is a collaboration between the National University of Singapore Society (NUSS) and Strategic Moves.