It's what gives the coronavirus its unmistakable look

and scientists think it may be the key to why new variants

of the virus are becoming more transmissible.

- A new study by the CDC is raising the alarm

on the coronavirus variant spreading across the country.

- The fast-spreading COVID-19 variant

first found in the UK is now evolving in a way

that could make existing vaccines less effective.

- [Reporter] New research shows

that the more transmissible variant from the UK,

called B117, will likely become the most common version

of the virus in the US.

- The big concern is that, with more transmissible variant,

you have more cases and you have more chance

for superspreading events and epidemic surges

which overwhelm our healthcare systems.

- [Reporter] Here's the science

behind why these new variants are spreading faster

and what this could mean for vaccines.

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Like other viruses, when the coronavirus replicates,

small genetic mistakes, or mutations, can occur.

- You can be almost certain

that as long as there's a lot of virus

circulating in the community, there will be the evolution

of mutants because that's what viruses do.

- Many of those do nothing.

Some of those actually confer a survival benefit

for the virus to transmit more effectively, for instance.

- [Reporter] Abraar Karan is a global health physician

who has been studying the coronavirus pandemic.

- And so, as it does that,

it has a better chance of spreading to new hosts

and continuing to replicate in those hosts.

- [Reporter] Karan says this is likely what is happening

with the new, more transmissible variants

appearing around the world.

Recent research has shown that a number

of these new versions of the virus have mutations

that affect the spike protein.

Take a look at this model of the coronavirus.

You can see each spike protein

is made up of three identical parts known as protomers.

These protomers have the ability to change their position

from closed to open, affecting how easily

they can bind to and infect human cells.

- You can visualize it like a flower.

So you've got petals on the outside,

the really obvious thing that you see.

There are three of them.

The three of them have to bind to the receptors.

- [Reporter] Jeremy Luban is a virologist

who studies the coronavirus.

He explains that when the protomers are down,

infection is more difficult.

But when these parts are up and open, it's much easier.

In the first version of the coronavirus

that originated in China in 2019,

these protomers usually had a closed shape,

which may have made it less transmissible

than some more recent versions of the virus.

This is another view of a spike protein

that helps to show where these mutations occur.

In the winter of 2020,

one mutation, known as D614G, emerged.

It appears in this region of the spike protein.

This mutation made it more likely for the spike

to have an open shape, increasing the virus' ability

to infect human cells.

Soon after the mutation emerged,

variants that had it took over.

- So by June, pretty much all the viruses around the planet

had this change, this mutation.

Our belief is that it supplanted the original virus

because it was more transmissible.

- [Reporter] Luban thinks this is what is happening

with some of the new variants

that are emerging around the world as well.

- In the United Kingdom,

that variant really expanded very rapidly.

It was first seen in September

and now it's the dominant version of the virus

circulating in the United Kingdom.

Does indeed appear as if the same thing happened

in South Africa.

- [Reporter] Another element

that affects the spike protein is antibodies.

These are proteins that defend the body

against the coronavirus by blocking the ability

of the spike protein to attach to cells,

which prevents the virus from infecting.

Antibodies are produced by the immune system

in response to infection or vaccines,

and so far, the new coronavirus variants

scientists are worried about all have mutations

that affect the spike protein.

Here are some that scientists are focusing on.

The first is called N501Y, which was first detected

in the variants from the UK and South Africa

in the second half of 2020.

This mutation is located in a region of the spike protein

known as the receptor binding domain, or the RBD.

This is the main location

where the virus attaches to human cells and infects them.

The N501Y mutation seems to be helping the virus bind,

which could help explain the higher transmissibility.

The second mutation

that scientists are focusing on is called E484K.

It's found in variants

from South Africa and Brazil and reduces the ability

of certain antibodies to bind to the RBD,

which helps the virus' chances of infecting cells.

- What the antibody recognizes is the shape.

If you're playing with blocks and you have triangles

and circles and you have to fit them

into the appropriate holes,

you can't fit a circle into a triangular hole.

It's analogous to that.

If the virus then changes

so that it's no longer a triangular hole

but it's a circular hole,

then the antibody will no longer fit.

- [Reporter] Scientists have also found

that some of the new coronavirus variants have parts missing

in a region that comes off the side of the spike protein.

This is known as the N-terminal domain.

- Some of those mutations

are removing surfaces of the protein

that other antibodies bind to.

If the virus mutates that surface or deletes it,

those antibodies are no longer going to work

to block the virus.

- [Reporter] Scientists say this may help explain

why current vaccines may be becoming less effective

against some new variants.

This is why experts are urging caution.

- Variants are gonna continue emerging

and we need a public health strategy that addresses it.

We have to focus on getting better ventilation.

We have to get people better personal protection;

better, higher-grade masks that can filter better;

we have to test; we have to trace;

we have to isolate the fundamentals of epidemic control.

- [Reporter] And Karan says that while vaccines

should still be effective in preventing severe illness,

a booster variant shot may be needed later in the year.

- They work extremely well right now,

right, With Moderna and Pfizer 95% vaccine efficacy.

They will start to work less well

against some variants into the future,

but that is to be expected

and that is why vaccines will be a major part

of COVID control for the foreseeable future.

- [Reporter] Experts continue to emphasize

the importance of getting vaccinated

along with other strategies to keep transmission low

and stop the spread.

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