Why different strains of COVID-19 are so common now

YesYou’ve probably read a lot about the new strains of the coronavirus cruising the world these days, from Brazil to South Africa. You’ve probably also heard a lot of comments about the possibility that these mutations will render our vaccines irrelevant as we finally begin to scale up vaccination programs. But unlike some of those creepy headlines, the reality of when and why SARS–CoV–2 (i.e. the novel coronavirus) is mutating and what that means for vaccines is much more nuanced – and probably not as apocalyptic as some news reports might have you believe. We spoke with top virologists to find out everything you need to know about the different strains of COVID-19, and here’s what they had to say:

How and why viruses mutate

When you get sick with a virus like the novel coronavirus, “it’s not really a unique virus. [particle] that infects you. It’s a population of viruses, ”says Richard Kennedy, PhD, virologist and vaccine researcher at the Mayo Clinic in Rochester, MN. You could be infected with 100 or even 10,000 different virus particles. Each particle has its own slightly different genetic code, just like two people have slightly different genetic codes.

Changes to this code only occur when the virus replicates, that is, copies itself to survive. To replicate, a virus needs two things: a human cell (whose machinery it hacks to help itself replicate) and a specific enzyme that it brings to copy its genome (essential to the replication process). This enzyme acts like a cheap copier, says Dr. Kennedy. “This copier is not really good. He makes mistakes left and right, ”he adds. These genetic errors end up being encoded in the genome of all new viruses created in that single infected cell.

These errors happen quite regularly and at random. Many come and go because they don’t give the virus any real benefit; some even make the virus less able to infect a cell. “Most mutations are expected to have no impact on the function of the virus or the way we experience it,” says Lucy van Dorp, PhD, pathogen evolution expert and senior researcher in the department. of Genetics from University College London, Evolution and Environment.

Sometimes, however, a mutation creates an advantage for the virus. “Maybe the virus can infect other cells faster, or it attaches to cells a little better. It survives a little longer in the environment or produces more viruses, ”explains Dr. Kennedy. Because all variants of the virus try to compete for the same number of cells that can be infected in a person’s body, beneficial mutations allow one variant to outperform other viruses. Eventually, this strain becomes the predominant variant in a person’s body – and becomes the variant that spreads to other people, says Dr. Kennedy.

How well a given mutation spreads from there depends on several factors, says Dr. Kennedy, including how beneficial the mutation is for the virus and how many people can potentially catch the variant. “Most are not going anywhere,” he says. “It’s the [variants] that appear, then are at 5%, 10%, 90% – these are the ones we are worried about, because it suggests that they have an advantage and that is why they are spreading through the population. And given that to date there have been over 27 million cases of the coronavirus in the United States alone, giving the virus enough time and opportunity to mutate – and for these more beneficial mutations to come together. develop.

The different strains of COVID-19 that scientists are monitoring

Scientists around the world are tracking mutations (known as genomic surveillance) at different rates. The UK, for example, currently sequences the genome in 47.3 out of 1,000 COVID-19 cases, while the US sequencing 3.23 out of 1,000 cases. Tracking the genome of the virus allows scientists to identify and to quickly isolate new variants and update vaccines accordingly.

The United States Centers for Disease Control and Prevention (CDC) is actively monitoring three strains, as they have all been found in the United States and so far appear to be spreading faster than the other variants.

United Kingdom (UK) variant B.1.1.7

First sequenced last fall and found in the United States in December, some researchers say the British variant is 50 to 75% more transmissible than the original virus. “We are paying special attention because there are several spike protein mutations,” says Dr. Kennedy, referring to the unique protein structure on the outside of the coronavirus that is used to enter and infect cells. “There is some evidence that makes this variant more transmissible – that infected people contain more virus and have a higher viral load,” says Dr. Kennedy. Indeed, a January report from the CDC estimated that without further measures to verify its spread, the UK variant could become the predominant variant in the US by March.

Some UK researchers initially reported that this variant may be 30-40% deadlier than previous variants, although these studies are small and inconclusive. “Time will tell as we accumulate more information about the virus,” says Dr Kennedy.

South Africa, variant B.1.351

The South African variant shares some mutations with the British variant. Some researchers have also expressed concerns about its ability to evade antibodies (proteins released by the immune system to attack foreign invaders like viruses), potentially reducing the effectiveness of current vaccines.

“The South African variant has at least three mutations, and they are found just where the spike protein binds to the cell receptor,” says Dr. Kennedy. “It is [the area] where neutralizing antibodies, from infection or vaccination, are targeted. The problem, he says, is that mutations at this crucial location in the virus could help it avoid antibodies. If this theory comes to fruition, it could mean that our current vaccines are not as effective (as they generate antibodies that might not be effective against this mutation), so you could be re-infected with this variant even if you have it. have already been. sick or vaccinated against COVID-19.

Brazil variant P.1

With more mutations than the British or South African variant, the Brazilian variant may be better at avoiding antibodies produced by the body to clear it, which could potentially make the virus more deadly. “The Brazilian variant has exactly the same three mutations in the spike protein [as the South African variant]so it is likely that we will also see a decrease in the neutralizing capacity of it, ”says Dr. Kennedy. “Once we start immunizing, if it starts to escape some of the vaccine protection, then it will probably continue to circulate in the community somewhat. But what happens if he accumulates more mutations? This is still the problem.

What this means for vaccines

Everything about the new variations looks worrisome, but scientists stress that the different strains of COVID-19 shouldn’t prevent the average person from sleeping at night. Indeed, some experts claim that we just don’t have enough data yet to know how these new variants are going to affect us, period. “Neither the increased transmissibility nor the mortality of the new viral variants has been proven,” says Theodora Hatziioannou, PhD, a Rockefeller University virologist who studies the new variants.

Here’s how vaccines work, including some of the newer COVID-19 vaccines:

Likewise, there is mixed evidence that these strains of COVID-19 could affect the effectiveness of available vaccines. In January, biotech company Novavax released the results of its phase three trial of the coronavirus vaccine. His vaccine was nearly 90% effective in the United States and the United States, but only 60% in South Africa. “Part of this could be due to different populations and different underlying health issues,” says Dr. Kennedy. “But it may also be because the South African variant was present.” Johnson & Johnson’s phase three clinical trial results show its single-dose vaccine was 72% effective in the United States but 57% in South Africa, where, the company noted, 95% of COVID cases -19 were related to the South African variant. at the time of trial. And AstraZeneca has just suspended the deployment of its vaccine in South Africa after its trial found that the vaccine offered “minimal protection” against mild to moderate cases.

“This is already data suggesting that vaccines will not be as effective. But the flip side is 57 to 66 percent, which is much better than 0 percent, ”adds Dr. Kennedy.

For now, the CDC says the antibodies produced by existing vaccines appear to recognize the major variants and therefore would be able to fight them. But other studies are underway to better understand the effectiveness of the vaccines used and developed against these strains. In addition, pharmaceutical companies are designing new vaccines to treat the South African variant, while the Food and Drug Administration (FDA) is preparing a rapid review process for the rapid approval of booster injections if current vaccines prove to be successful. ineffective against new variants of coronavirus.

“It’s going to be a continuous race. What will likely happen is that, just like the flu, we may need to regularly change the vaccine strain used, so we may need a COVID-19 vaccine every two years. They will just keep changing it to keep pace with the changes, ”says Dr. Kennedy. There are also good reasons to hope that existing vaccines will continue to tame the pandemic. The Johnson & Johnson Phase Three trial, for example, found that people who fell ill after vaccination had less severe illness.

How to protect yourself

Ideally, approved vaccines will continue to be mass produced and rapidly distributed as scientists fuel an ongoing pipeline of new and improved vaccines. The problem remains that scientists do not yet know whether vaccines are preventing you from spreading the virus. “You might still have a virus in you and be able to pass it on, but you just don’t have any symptoms. This is especially true given that this virus is mutating and already evades at least some immune protection, ”says Dr Kennedy.

Because the virus can mutate and produce new variants only when it infects a person, the only way to prevent the emergence and spread of new variants is to reduce transmissions, says Dr Kennedy. This means that it is essential for all of us to continue masking (or even double masking for stronger protection) and social distancing, even though we have already been vaccinated. “It’s painful, boring, and uncomfortable, but if we’re going to beat this pandemic, that’s basically the only way to do it,” says Dr Kennedy.

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