The COVID-19 virus is changing. What does this mean for vaccines?

A nurse prepares to vaccinate a health worker at the Berks Community Health Center in Reading, Pennsylvania on January 6 Credit – MediaNews Group via Getty Images – Copyright – 2021 Image MediaNews Group

As we enter the second year of life with the novel coronavirus SARS-CoV-2, the virus celebrates its invasion of the world’s population with even more mutated forms that help it spread more easily from person to person. ‘other.

One, first detected in the UK in December, has already sounded the alarm that the COVID-19 virus is now eluding the protection that vaccines just rolled out now could provide. The variant has also been found in the United States Already, UK authorities have tightened lockdowns in England, Scotland and Wales, and over the holidays more than 40 countries have banned travelers from the region in an attempt to ‘prevent the new strain from spreading to other parts of the world. Health officials are also concerned that a different strain found in South Africa may become more resistant to vaccine protection. This variant includes a few mutations in key areas that the antibodies, generated by the vaccine, target.

It is not yet clear exactly how the new strains affect those infected – such as whether they develop more severe symptoms – and whether they can lead to more hospitalizations and deaths. But scientists are redoubling their efforts to genetically sequence more samples from infected patients to find out just how widespread they are. So far, there are enough clues to worry public health experts.

The fact that SARS-CoV-2 is turning into potentially more dangerous strains is no surprise. Viruses mutate. They must in order to compensate for a critical omission in their composition. Unlike other pathogens such as bacteria, fungi and parasites, viruses do not have any of the mechanisms to reproduce further, so they cannot reproduce on their own. They fully rely on the hijacking of the reproductive tools of the cells they infect to generate their offspring.

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Being such freelancers means that they can’t be picky about their hosts and have to be content with whatever cellular equipment they can find. This usually leads to a flurry of errors when they sneak around to copy their genetic code; as a result, viruses have some of the most sloppy genomes among microbes. Most of these mistakes are meaningless – false starts and dead ends – that have no impact on humans. But as more and more mistakes are made, the chances of one improving the virus by passing from person to person or pumping out more copies of itself increase dramatically.

Fortunately, coronaviruses in particular generate these genetic errors more slowly than their cousins ​​like influenza and HIV – scientists sequencing thousands of SARS-CoV-2 samples from COVID-19 patients found the virus to be around two errors per month. Yet this has so far led to around 12,000 known mutations in SARS-CoV-2, according to GISAID, a public genetic database of the virus. And some, by sheer coincidence, end up creating a greater threat to public health.

Just months after SARS-CoV-2 was identified in China last January, for example, a new variant, called D614G, replaced the original strain. This new version has become the dominant version that has infected much of Europe, North America and South America. Virus experts still do not know how important D614G, named for the location of the mutation on the viral genome, has been to human disease. But so far, blood samples from people infected with the strain show that the virus can still be neutralized by the immune system. This means that vaccines currently being deployed around the world can also protect against this strain, as the vaccines were designed to generate similar immune responses in the body. “If the public is wondering if vaccine immunity is able to cover this variant, the answer will be yes,” says Ralph Baric, professor of epidemiology, microbiology and immunology at the University of North Carolina at Chapel Hill, who has studied coronaviruses for several decades.

The so-called N501Y variant (some health officials also call it B.1.1.7.), Which was recently detected in the UK and US, may be a different story. Based on laboratory and animal studies, researchers believe this strain can spread more easily between people. This is no surprise, says Baric, because so far most of the world’s population has not been exposed to SARS-CoV-2. This means that for now, strains that jump better from person to person will have the benefit of spreading their genetic code. But as more people are vaccinated and protected against the virus, that may change. “The selection conditions for the evolution of the virus currently favor rapid transmission,” he says. “But as the human population becomes immune, selection pressures change. And we don’t know which direction the virus will go. “

In the worst case, these changes could cause the virus to become resistant to immune cells generated by currently available vaccines. The current mutants are the virus’s first attempts to maximize its co-optation of the human population as viral copiers. But they could also serve as the backbone on which SARS-CoV-2 builds a more lasting and stable takeover. Like a prisoner planning a jailbreak, the virus bides its time and destroys the defenses the human immune system has built. For example, the virus can mutate in a way that changes the makeup of its spike proteins – the part of the virus that antibodies in the immune system try to stick to to neutralize the virus. And this mutation may not be enough to protect the virus from these antibodies. But two or three might.

The biggest concern right now, says Baric, is that there are already two or three variants of SARS-CoV-2 that have mutations in these precise places, “where additional mutations can make a more significant change in terms of transmissibility or virulence.

The best way to monitor this is to sequence the virus in as many infected people as often as possible. Only by tracking the evolution of SARS-CoV-2 can scientists hope to stay ahead of the most dangerous and potentially deadly mutations. In November, the U.S. Centers for Disease Control (CDC) launched a sequencing program that will require each state to send 10 samples every two weeks from infected people, in order to more consistently track any changes. SARS-CoV-2. genome. But it is a voluntary program. “It’s still not a national effort, it’s voluntary, and there is no dedicated funding for it,” says Baric. “Come on, we’re in the 21st century – let’s step into the 21st century.”

Without substantial federal funding dedicated specifically to sequencing the genomes of SARS-CoV-2, most work in the United States is currently being done by scientists at academic centers like the Broad Institute of MIT and Harvard and the University of Washington. Since early last year, the CDC has been working to better characterize SARS-CoV-2 viruses from patient samples in partnership with some of these university labs, as well as with the health departments of State and local and commercial diagnostic companies, in the SARS-CoV- 2 Consortium SPHERES (Sequencing for Emergency Response in Public Health, Epidemiology and Surveillance) “If we sequence one in 200 cases, we are missing a lot of information, ”says Baric. “If we sequenced about 20% of the cases, then we could start to see something and we would be in the ball game to find new variations. We could probably do a better job here in the US ”

Other countries are also working on this effort. The UK has long been a leader in gene sequencing, and probably through its efforts, it was able to identify the new variant quite soon after it emerged. Scientists around the world have also published genetic sequences for SARS-CoV-2 in the public GISAID database.

Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical adviser to President-elect Joe Biden, says his teams are sequencing and studying the new variants to better understand the effect they might have on disease, how they might be close to causing more serious disease and, more importantly, as more people get vaccinated, whether the new variants may escape the protection of the vaccines we know they are. operate today.

The good news is that if the mutant strains become resistant to current vaccines, the mRNA technology behind Pfizer-BioNTech and Moderna should allow companies to develop new injections without the same lengthy development and testing as the originals required. “The mRNA platform is extremely flexible to turn around,” says Fauci. If a new vaccine were needed, it would be treated by the Food and Drug Administration as a strain change in the virus target, in the same way that influenza vaccines are changed every year. “You could get it out pretty quickly,” says Fauci, after showing in tests with a few dozen people that the new vaccine produces satisfactory amounts of antibodies and protection against the mutant virus.

Tracking every change the virus makes will be key to buying the time it takes to move vaccine targets before SARS-CoV-2 jumps too far for scientists to catch up with. “We take [these variants] seriously and we’ll be monitoring them closely to make sure we don’t miss a thing, ”Fauci says.