What Does the Advent of Mutant Coronavirus Strains Mean for Vaccine Efficacy (Best- and Worst-Case Scenarios)?

Written By Humayra Ali

A new mutant strain of SARS-CoV-2, the virus that causes COVID-19, is sweeping across the United Kingdom (UK) rapidly. This mutant virus, named the B.1.1.7 lineage, has also entered dozens of other countries, including the United States (US). The UK variant has accumulated many mutations much quicker than the original strain. 

Meanwhile, a second mutated strain of coronavirus, which is potentially a more contagious variant of COVID-19, was discovered in South Africa on December 18, 2020. According to the British health authorities, the South African mutant variant, which is called 501Y.V2, has already spread to the UK. The Centers for Disease Control and Prevention is monitoring whether the South African mutant virus has reached the United States. 

Now we are left with pondering what it all means? The most obvious question being, will the current vaccines still work against the mutants? If in the event the current vaccines aren’t potent enough, what would be the solution?

About the New Mutant Coronavirus Strains

The RNA viruses mutate very frequently because they carry proofreading proteins that are heavily prone to making errors during genome replication. Mutant viruses emerge when there are alterations or changes in the genetic material, in this case, the RNA genome of the coronavirus, that carries codes or instructions for making proteins that play important roles in the virus life cycle. Some of these proteins are structural building blocks that make up the virus particle. Understanding the structural changes that have occurred due to the mutations is important for understanding how the current vaccines may affect protection against these new strains.

In the UK variant, 23 mutations have changed 4 viral proteins, including the spike proteins found on the surface of the coronavirus. As a matter of fact, 8 of these 23 mutations affect the spike protein. 

As for the South African mutant strains, researchers are trying to characterize the genetic alterations and investigate whether it affects the efficacy of the current coronavirus vaccines. Early analysis suggests this strain is more transmissible and carries a heavier viral load than the original (ancestor) strain. We are not sure whether this new strain causes more severe symptoms.

The spike protein enables the virus to enter human cells. The current mRNA vaccines developed by Pfizer/BioNTech and Moderna are designed to recognize and bind to just the spike proteins, subsequently triggering and teaching the immune system to build protection against coronavirus infection. In other words, the spike proteins are a key target of our immune response to fight off the coronavirus during infection as well as to protect from any future infection following vaccination.

As the spike proteins of the coronavirus mutate, the shape of the protein changes. When the shape changes, the ability of the coronavirus to infect our cells may be affected, for good or for worse. Imagine if the changes are advantageous for the virus such that it makes it easier to enter our cells, then the virus too can be transmitted more easily from one person to another. 

Infographic created by Vaxtherapy.com

Infographic created by Vaxtherapy.com

Now, keep in mind that just because the virus transmits or spreads more easily, doesn’t necessarily mean it is more virulent or dangerous—though it could be both virulent and easily transmittable without any interdependencies. The UK officials say that the new virus may be up to 70% more transmissible than the original virus, but it is still too early to say anything definitively. In any case, the mutations may however affect how well our immune system combats the virus and potentially reduce the potency of the current vaccines.

Do the Mutations of the New Coronavirus Strains Reduce the Effectiveness of the Current COVID-19 Vaccines? 

Mutation induced changes in viruses have proved to be an ongoing challenge for the development of seasonal flu vaccines. We end up creating less effective flu vaccines every year. But the good news is, even with less than optimal vaccines, we can reduce the likelihood and the severity of the disease. 

The way to think about this is, how effective will the current coronavirus be against the mutants as opposed to will they be effective or not. The quickest way to test this is to take blood samples from those who are vaccinated with the current vaccines and see whether the antibodies in the blood, which were generated as a result of the immune response to the vaccines, can bind the mutated spike proteins and neutralize the mutant viruses. If the antibodies can still bind and neutralize the mutant variants, then the current vaccines would work against the mutants. 

Pfizer and BioNTech, has already started testing, though it can take a few weeks to get the results. Moderna will be doing additional testing as well. But based on available data, both companies believe that the current vaccines will work against the mutant strains. Fingers crossed! 

In the Worst-Case Scenario, What Happens if the Mutant Strains Can Evade Attacks From the Current COVID-19 Vaccines? 

In the unlikely scenario that the new mutants can escape attacks from the current Covid-19 vaccines, there is still hope! In that case, vaccine makers will have to return to the drawing board—which is not an uncommon endeavor in the field of vaccines. Take the vaccines for influenza (flu) viruses as an example. Scientists go back to the drawing board every year to modify the seasonal flu vaccines because this virus mutates quite rapidly.

Thanks to the advances in research, Pfizer, BioNTech, and Moderna are all using a new type of mRNA-based technology for vaccines that can be quickly adapted as the virus mutations pop up. Unlike many other vaccines that rely on weakened or dead viruses that have to be grown in large amounts, this mRNA molecule can simply be tweaked as needed and put back into the vaccine. For example, current mRNAs can just be swapped with the new code for the mutant spike protein and that’s it—nothing else changes. Vaccine makers think it will take perhaps even less than 6 weeks to adjust the vaccine this way for any new mutant variants, that is if needed. Regulatory approval, however, may take longer, unless of course urgency and high priority are given for expedited approval.

With the Introduction of Mutant Viruses, it is Now All That More Important to Get Vaccinated As Soon As Possible

Increased transmissibility of the mutant strains means that COVID-19 will spread more quickly, and more people will be getting sick faster. We now have witnessed that the coronavirus spike protein can change drastically in a short time. It is critical that more people are vaccinated to achieve herd immunity (herd protection), prevent this virus from evolving further, and get this pandemic under control.

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Disclaimer: Vaxtherapy is NOT affiliated with any of the pharma/biotech companies working on COVID-19 vaccines. The purpose of this post is to provide education and awareness from a virologist’s independent perspective based on available facts and data.

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