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Don't focus on herd immunity, vaccination should be comprehensive: COVID-19 panel expert

Don't focus on herd immunity, vaccination should be comprehensive: COVID-19 panel expert

Associate Professor Lim Poh Lian, an infectious diseases outbreak expert, dressed in personal protective equipment. (Photo courtesy of A/Prof Lim)

SINGAPORE: Rather than aim for a certain percentage of the population to be inoculated to achieve COVID-19 herd immunity, Singapore should vaccinate as many people as possible. 

In an interview with CNA, Associate Professor Lim Poh Lian, who is on the Expert Committee for COVID-19 Vaccination, said that it's a "mistake to focus on percentages" when it comes to COVID-19 vaccination.

“I think the optimum outcome is that we vaccinate everybody in Singapore that we can safely vaccinate and who's willing to be vaccinated," she said, days after Prime Minister Lee Hsien Loong announced that the first shipments of a COVID-19 vaccine should arrive in Singapore by the end of the year.

Herd immunity, a term that has been much discussed since the pandemic started, refers to how a virus peters out when sufficient people in the "herd", or community, are protected against it.

READ: Pfizer-BioNTech COVID-19 vaccine approved by Singapore, first shipment expected by end-December

It means that there will not be outbreaks raging in the community, but it doesn't mean that there are no cases or small clusters, said Assoc Prof Lim, a senior consultant and head of the Travellers’ Health & Vaccination Clinic at Tan Tock Seng Hospital.

“Even if we get 70 per cent or 80 per cent of the population vaccinated, four people you see might be fine but that fifth person is not okay. That person would get hurt, they would get sick they could end up in the ICU on a ventilator," she said. 

Associate Professor Lim Poh Lian, senior consultant and head of the Travellers’ Health & Vaccination Clinic at Tan Tock Seng Hospital. (Photo courtesy of A/Prof Lim)

The director of the National Centre for Infectious Diseases’ (NCID) High Level Isolation Unit has been on the frontline of the fight against COVID-19, treating patients and providing public health consultancy. She previously served on the United Nations Global Health Crises Taskforce and the World Health Organization (WHO) Global Outbreak Alert and Response Network (GOARN) Steering Committee.

As a member of the Expert Committee for COVID-19 Vaccination, she gives advice on the medical aspects of vaccination and how that might affect public health guidance, operations and communication with patients and the public. It's an extension of her work on the Ministry of Health's expert committee on immunisations for more than 10 years.

Assoc Prof Lim is also the doctor who connected the dots that led to the diagnosis of Singapore's first case of monkeypox last year.

The monkeypox detective: Doctor who helped identify Singapore’s first case was alerted by patient’s rashes

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She was given an honourable mention at the 2020 Healthcare Humanity Awards, an event that salutes exemplary healthcare workers, caregivers, and volunteers.

The award also recognised her compassion for the sick and the underprivileged beyond her profession – in 2018, she adopted Keyuan, now named Lucas, a hearing-impaired orphan from China after hearing about his plight in a CNA documentary.

Associate Professor Lim Poh Lian and her son Lucas Yap Keyuan. (Photo courtesy of A/Prof Lim)

Assoc Prof Lim, who has three other children aged 18 to 20, said that she wants people to know that the vaccines are safe and that she would give it to her family.

“It's effective and we will ourselves take it. I would give it to my family as soon as it is offered to them … because we’re offering (vaccines) from the highest risk to the lowest risk," she said.

She emphasised that the vaccines had undergone meticulous review by Singapore's Health Sciences Authority (HSA) and the expert committee, as well as authorities overseas such as the Food and Drug Administration of the United States.

READ: Data on Pfizer-BioNTech COVID-19 vaccine 'robustly and thoroughly reviewed', says HSA 

READ: Moderna confirms agreement with MOH to supply Singapore with COVID-19 vaccine

"It's normal to feel hesitant when there's a new vaccine, but we're really living in extraordinary times with a pandemic raging in many countries around the world. 

"If we want to reopen Singapore safely, our society, our economy, our borders, then vaccines are a really important means of protection to protect ourselves, and also those that we love and care about," she said. 

The biggest challenge for now was getting a double dose of the vaccine to about 5 million people, she said. Singapore has a population of 5.69 million.

"We've never done that before ... when we vaccinate, every birth cohort is about 35,000 to 50,000 kids. So to go from 50,000 kids a year to 5 million in one year. It's really a huge challenge," she said.

READ: Pfizer-BioNTech, Moderna and Sinovac: A look at three key COVID-19 vaccines

HSA has recommended that the vaccine be administered to people above 16, excepting pregnant women and people with compromised immune systems, pending safety and efficacy data on these groups of people.

In addition, people with a history of anaphylaxis or the rapid onset of severe allergic reactions should not receive the Pfizer-BioNTech vaccine as a precautionary measure.

Assoc Prof Lim said Singapore will be watching for the short-term side effects, such as anaphylaxis and serious allergic reactions, even as the vaccines are deployed. She added that while people may focus on the risk of taking the vaccine, they also need to think about the risk of contracting COVID-19.

The current low number of cases may lull people here into a sense of security, but she said this was the best time to get everyone vaccinated. That's because there may be a rush for vaccinations if the number of COVID-19 cases start to rise, and people may not be able to get a vaccine then even if they wanted one.

For both vaccines which are the frontrunners to be administered around the world, developed by Pfizer-BioNTech and by Moderna, two doses are required some weeks apart. One would not get the full protection until seven to 14 days after the second dose, she explained.

“We really want to encourage people during this time when ... things are still safe and calm, to get the vaccine, because the time to get the vaccines is not when things are raging – ideally."

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People should also be aware that the vaccines require two doses to work effectively, she said.

“If you get a pretty sore arm in  the first one and then you have to go again for your second helping in three weeks’ time, I suspect that some people may not want to go. What we want to really emphasise to people is that the vaccine is a two-dose series," she said.

"One dose is not enough, you need to complete two doses for the full protection, and for the protection to be as long-lasting as possible."

So if as many people as possible get vaccinated, will life resume some semblance of normalcy in Singapore?

Assoc Prof Lim said that a successful vaccine roll-out will help life get "closer to normal", but all the precautions will continue for some time to come. After all, the vaccines are - not 100 per cent - effective, and there are still segments of the population who cannot, or will not, be vaccinated.

"So we need to keep our masks up, we need to keep the safe distancing thing ... until COVID is actually controlled worldwide, I think we're going to have to keep our guard up for quite some time."

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Source: CNA/hm


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