Q & A: Who should be given the coronavirus vaccine first?

A photo from Feb 10, 2020, shows laboratory technicians working on a diagnostic kit to test whether patients have the coronavirus at the Agency for Science, Technology and Research’s Diagnostics Development Hub.
A photo from Feb 10, 2020, shows laboratory technicians working on a diagnostic kit to test whether patients have the coronavirus at the Agency for Science, Technology and Research’s Diagnostics Development Hub.PHOTO: ST FILE

Professor Wang Linfa, director of the programme in emerging infectious diseases at the Duke-NUS Medical School, answers some pressing questions on Covid-19.

Q When will we likely have a vaccine?

A By the end of this year. It is possible because everybody's moving so fast. It used to take many months to crack the genome code of a new virus. Now, they can do it in two days. The Chinese made it available on Jan 9.

Q Why does it take so long to develop a vaccine? Can the vaccine developed for the 2003 Sars (severe acute respiratory syndrome) outbreak be used since the two coronaviruses are 80 per cent similar?

A No. Genetically, Sars and Covid-19 have 20 per cent difference. That difference is enough for the body to recognise only Sars but not Covid-19. It is much better to start developing a vaccine from scratch.

Q When a vaccine is available, will there be enough for everyone? If not, who should we give it to first?

A Most of the time when you have emerging infectious disease vaccines, you give to those at high risk first.

You also do what we call ring vaccination. For example, in a nation like South Korea, you do not vaccinate everybody. You vaccinate the churchgoers and those associated with the church, and maybe Daegu city and the healthcare workers in that city first.

We want to vaccinate the population pre-emptively. Of course, we want to prevent people from getting sick and dying. But equally important is to stop the transmission.

It is really about identifying the key transmission events and who are at most risk to transmit. If we vaccinate these populations first, we not only save them, but more importantly, prevent further transmission.

Q If I get a vaccine for Covid-19, will it last me for a lifetime or is it like the flu vaccine where you have to get one jab every year?

A There are two different scenarios.

One is lifelong immunity. Some viruses can produce that, like the measles virus. If you are infected with measles, then you get lifelong protection.

Other viruses, when you get infected, you will get protected for a few years, maybe.

With the flu, every year you get a jab because the flu virus is changing. So, one year, you get a vaccine against one type; the next year, if it is a different type, you need a different vaccine. It does not mean the immunity has waned, it is immunity against that particular seasonal flu, so you need to have another injection.

VACCINATE MOST-AT-RISK FIRST

It is really about identifying the key transmission events and who are at most risk to transmit. If we vaccinate these populations first, we not only save them, but more importantly, prevent further transmission.

PROF WANG LINFA, on who to vaccinate.

Q Which is likely for Covid-19? Will it change much and will different vaccines be needed over the years?

A If there is any kind of silver lining, it is that this virus looks like it does not change as rapidly as Sars and Mers (Middle East respiratory syndrome). It is genetically relatively stable. And that is good in terms of developing tests and vaccines.

If the virus changes rapidly, even if you have a vaccine, you may not be able to predict the next variant. In 40 days, over 100 genome sequences - the whole genetic code of the virus - has been deposited in the public gene bank.

These are not only different generations of the virus, but also those from different geographic locations. It looks like it is stable so far.

Q Can Covid-19 be contained?

A This is difficult to answer. Developed nations may be able to contain it, but developing nations may not be able to do so. It is worse if there is a super-spreader, who may infect 30 people when most patients infect just three.

Q Did the virus come from an animal and, if so, which animal?

A It is very clear that it is a zoonotic transmission. It is not a human virus, it is an animal virus that got into the human population.

Originally from bats, but most likely, there is another animal in between... This is a hot area (of research) and so far, we do not have enough data.

A version of this article appeared in the print edition of The Sunday Times on March 01, 2020, with the headline 'Who should be given the vaccine first?'. Print Edition | Subscribe