February 05, 2021 BY CYNTHIA DEMARCO
New strains of the SARS-CoV-2 coronavirus that
causes COVID-19 have
already been identified in four different countries, including the United
States. Early reports indicate that these mutations may be more contagious than
the original coronavirus strain that first emerged in late 2019.
So, what does that actually mean for the future of the
pandemic? And what does it mean if you’ve already been vaccinated or plan to
get one of the COVID-19 vaccines? Will
the current vaccines be effective against the coronavirus’ mutations? And, how
can you protect yourself against future mutations?
We spoke with infectious diseases specialist and head of
Internal Medicine David Tweardy, M.D., for answers.
How do viruses mutate?
In order for a viral infection to be “successful,” the
virus has to bind to a human cell and have its nucleic acid (mRNA) enter inside the cell
where the mRNA is replicated many times over. The enzyme that replicates the
viral mRNA is brought into the cell by the virus itself.
But much as with typing a message, the results aren’t
always perfect. You can make a certain number of errors in your
words-per-minute rate and still be considered a pretty good typist.
Enzymes have a modest rate of “typing errors,” too,
which is how mutations get incorporated into new copies of the virus. Every
mistake the enzyme makes in recreating the mRNA inside a cell is technically a
mutation.
Tell us about some of the new
mutations in the coronavirus that causes COVID-19.
Each of the strains that has raised concerns has had
multiple changes or mutations in its nucleic acid. But the mutations that are
most important are those within the portion of the viral mRNA that encode the
spike protein. That’s the part that sticks out from the virus, and is
responsible for binding it to the surface of a cell.
Each of the variants has at least one mutation in the
spike protein, as well as others elsewhere. The two most-talked-about variants
from South Africa and the United Kingdom have mutations in the spike protein
that make them more contagious.
When scientists talk about a mutation
being more contagious, what does that really mean?
At the molecular level, it means that a variant is able
to bind to the receptors on each cell a little more tightly and enter the cell
more efficiently. So, a higher percentage of the cells exposed to
that variant of the virus will actually become infected with
the virus.
In more practical terms, it means more people can get
infected by a variant, if they don’t take reasonable precautions. Because each
individual infected with the mutated virus can, in turn, infect more people
than someone infected with the original strain of the virus.
Existing variants appear to be able to infect the cells
lining the nose between 30% and 70% more efficiently. So, instead of the
original reproduction number of
between 2 and 3, the more contagious variants’ reproduction numbers are likely
to be between 3 and 5, or almost twice that.
That means these mutations make the coronavirus easier
to catch and spread to others, making it more important than ever to mask up, wash your hands, keep social distancing and
get a coronavirus vaccine, wherever it is available to you. This is especially
important for immunocompromised cancer
patients, who are at increased risk for severe complications if they get a
COVID-19 infection.
Will the current COVID-19 vaccines
work on any or all of the coronavirus mutations?
The studies I’ve seen reported in the media indicate
that the antibodies generated
by both the Pfizer and Moderna vaccines are able to neutralize both the United
Kingdom and South African variant strains. mRNA technology makes
it easy for scientists to adapt the vaccines to better respond to new
mutations, if necessary. I’ve heard that Moderna may develop a booster shot
that addresses these mutations, in case it’s needed.
What about the vaccines still in development
that aren’t mRNA vaccines?
I have no reason to believe that any of the new vaccines
in development will behave dramatically differently. These vaccinations should
work just fine, in terms of protecting individuals from serious infection.
What steps should people take to
protect themselves from current and future coronavirus mutations?
The longer the pandemic goes on and the more the
coronavirus spreads, the more frequently it will mutate. So, whether you’ve
been vaccinated yet or not, it’s important to continue wearing a mask, washing
your hands and social distancing. It will take all of us doing this, and as
many people as possible getting vaccinated, for us to help slow the
coronavirus’ spread, so we can ultimately reach herd immunity and
get back to some level of normalcy.
Request an appointment at MD
Anderson online or by calling 1-888-512-7249.
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