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Why does the coronavirus mutate? How do we stop it from becoming more dangerous?

You’ve probably heard of the new strains popping up around the world. What does it mean for us and our vaccination plans? An infectious diseases doctor breaks it down.

Why does the coronavirus mutate? How do we stop it from becoming more dangerous?

An electron microscope image shows SARS-CoV-2 (round gold objects), the virus that causes COVID-19, emerging from the surface of cells cultured in the lab and isolated from a patient in the US. (Photo: Reuters/NIAID-RML/Handout)

The COVID-19 pandemic has dramatically changed our lives. From mandatory mask-wearing to safe distancing, testing, tracing and isolating cases, we’ve all been doing our part for the past year in our own coronavirus special edition of Survivor to outwit, outplay and outlast the virus.

The approval and use of the Pfizer-BioNTech and Moderna vaccines by Singapore in recent months are further examples of how we’re slowly adapting to counter the spread of the disease.

There are two or three COVID-19 mutations happening every month.

But just as we’ve had to make changes to our daily lives, SARS-CoV-2 (the virus that causes COVID-19) has also been adapting – or rather, mutating – to ensure its survival.

“This virus is relentless. It is very smart and is always one step ahead,” said Dr Ling Li Min, an infectious diseases physician from Rophi Clinic.

Dr Ling was a speaker at a recent webinar under Mediacorp’s ongoing virtual health and wellness event Body And Soul Fair, where she explained just how vaccines work to contain the spread of COVID-19 as well as its effects on stopping it from mutating into future, more dangerous new strains.

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You would have heard about the new coronavirus strains, and how the authorities are warning that they are more easily transmissible. One, known as B117, was reported by the United Kingdom, while the other, B1351, has spread widely in South Africa. There has also been a Brazilian strain known as P1.

(Photo: Pixabay/fernando zhiminaicela)

So why and how do mutations happen? “All viruses mutate. It’s part of their survival tactic,” said Dr Ling. This process takes place when a virus infects a healthy person and replicates itself in its new host. Most of the time, the mutations are small and don’t affect the way the virus works.

But occasionally, errors occur when the virus reproduces, which is what a mutation is, she said. “The extent of error increases the more times the virus replicates. By infecting more people, the risk of replication errors increases,” she said.


Like a wrongly photocopied set of instructions, the new virus cell starts to behave differently from its parent cell. From there, two things can arise: A variant or a new strain. “A variant occurs when the replicated virus’ blueprint has changed but because the change is so slight, its behaviour is still very similar to its parent cell,” explained Dr Ling.

The new strains have the ability to transmit more rapidly, and perhaps, the ability to cause more severe disease but that still needs to be confirmed.

But when the errors are so great that the new copy’s behaviour is very different from its parent, you have a new strain, she said.

Since it takes many mutations and variants to form a new viral strain, you can expect the extent of errors to be high. The UK and Brazilian strains, for instance, are found to have 17 mutations, while the South African strain has undergone 21 mutations, shared Dr Ling at the webinar.

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As a result, the new strains tend to end up exhibiting “behaviours that are more virulent, more dangerous compared to the parent strain", said Dr Ling, adding that there are two or three COVID-19 mutations happening every month.

(Photo: Pixabay/Gerd Altmann)


Regardless of the strain, SARS-CoV-2 has spike protein that “sits outside the wall of the virus”, said Dr Ling. Studies have shown that after mutation, the spikes become “flatter so the virus can enter a human cell more easily”. In other words, the virus is better able to evade the host’s immune system, she said.

For instance, the UK and South African strains contain a mutation that lets them bind more effectively to human cells, according to Dr Ling. Meanwhile, the South African and Brazilian strains are better at evading our immune system due to their mutations.

This virus is relentless. It is very smart and is always one step ahead.

Each time a new strain emerges, it is associated with increased clusters of COVID-19 cases, said Dr Ling. “They have the ability to transmit more rapidly, and perhaps, the ability to cause more severe disease but that still needs to be confirmed.”


The answer depends on how fast the vaccination take-up rate is. “If the rate of vaccination exceeds the rate of infection, it gives the virus less of a chance to mutate,” said Dr Ling, bringing back the point that mutations occur when more people are infected.

(Photo: Freepik)

Already, some studies suggest that the Pfizer-BioNTech and Moderna vaccines may be “less effective against the South African strain”, said Dr Ling. However, both vaccines still work against the UK strain, according to studies, she added. “Neither company has released data regarding the Brazilian strain.”

So should you still get vaccinated? Definitely. Even for those who have recovered from COVID-19, Dr Ling’s advice is to still get the vaccine. “The duration of the immunity is so far unknown, although we expect it to last up to three months. Also, there have been cases of re-infection.”

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Since Mar 4, the fully vaccinated (completion of two doses) in Singapore stands at 3.8 per cent. “That’s slightly more than half a million that have been vaccinated, or about 10 per 100 persons,” she said. 

If we want herd immunity to work without the use of safe measures, we need at least 70 per cent of the population to be vaccinated, she said.

As it turns out, that goal is not just a Singapore-centric but a global one, said Dr Ling, for international travel to resume. And it is a way – or perhaps the way – to stay ahead of COVID-19.

The online Body And Soul Fair runs until Mar 21. For more details on other online shows and talks to catch, visit

Source: CNA/bk