COVID-19 vaccination delays could bring more virus variants and hamper efforts to end the pandemic

Scientists say the world has reached a precarious point in the Covid-19 pandemic, where the conditions are right for the emergence of new coronavirus variants that could complicate efforts to fight the disease.

The virus continues to spread rapidly in many parts of the world, even though segments of the population have acquired some degree of immunity after being infected or vaccinated.

Scientists say the combination – high rates of viral transmission and a partially immune population – promotes the emergence of potentially more transmissible or deadly variants. More transmission means more opportunities for the virus to evolve, they say.

“If everyone is immune then you have almost no viruses circulating and the virus cannot adapt,” said University of Bern molecular epidemiologist Emma Hodcroft, adding that if no one in within a population is immune, so there is no pressure on the virus. to evolve. “This middle part, where you have a partially vaccinated population, or a partially immune population with a lot of virus circulating, is kind of your danger point,” she said.

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New variants could also reduce the effectiveness of Covid-19 vaccines and treatments and lead to re-infections in people who have already recovered from Covid-19, scientists say. The key to minimizing these problems, they say, lies in social distancing and other measures to reduce contagion as well as stepping up vaccination efforts, which have been behind schedule in many places.

“The slower you are at these two things, the more risk you take that you will have more variants emerging,” said Richard Lessells, infectious disease specialist at KwaZulu-Natal Research Innovation and Sequencing. Platform in Durban, South Africa, the group of scientists who sequenced the first South African variant, B.1.351.

When a virus infects someone, it creates many copies of itself. Whenever it does, errors can be introduced into its genetic code. Some of these errors, or mutations, have no effect on the behavior of the virus. Others – like some of those seen in the disturbing variants that have emerged in the UK, South Africa and Brazil – may enhance the virus’s ability to evade our immune system.

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It’s a matter of simple math: more inheritance means more mutations, and a greater likelihood of dangerous variants to take root.

“Each round of virus replication is an opportunity for it to incorporate a new mutation,” said Vineet Menachery, virologist in the medical branch of the University of Texas. “If you have fewer infected people and fewer cycles of the virus to replicate, fewer mutations can be introduced.”

And if the virus spreads uncontrollably within a population that has only partial immunity, then variants that have beneficial mutations – for example, those that help it evade the immune response – will have tend to predominate, say scientists.

This phenomenon, called selective pressure, may help explain how some of the newer coronavirus variants came about in the first place, and why South African doctors and scientists have reported seeing an unusually high number of suspected re-infections.

“That’s what we’ve seen play out here, almost certainly,” Dr Lessells said of South Africa.

Research by Dr Lessells and his colleagues showed that the B.1.351 variant initially spread most rapidly in South Africa’s Eastern Cape province, where many residents had already contracted Covid-19 and recovered. He and his colleagues have also shown in a series of lab experiments that antibodies from previously infected individuals were less effective against B.1.351 than earlier variants of the coronavirus.

Data from another study in South Africa appeared to support these findings, suggesting that previous infection may not fully protect against variant infection.

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Some researchers say the high number of mutations seen in the B.1.351 variant – over 20 – suggests that the mutations appeared in one patient before spreading to others.

Some scientists believe this to have happened in the UK, where a variant with around two dozen mutations emerged in December. An article published in the journal Nature documented the case of an immunocompromised patient whose Covid-19 infection persisted despite several months of treatment with convalescent plasma. Laboratory tests on viral particles taken from the patient showed that they had developed mutations that made them less vulnerable to antibodies.

This patient’s case shows how selective pressure can work within individuals as well as between populations, said Ravindra Gupta, professor of microbiology at the University of Cambridge and co-author of the article. In this patient, the virus learned to live with the patient’s antibodies through favorable mutations that occurred spontaneously, he said. What started out as a small mutation in a virus quickly grew into a lot more viruses because there was so much replication going on, he added. “There is the same with populations,” he says.

The rate of new Covid-19 infections in the United States has slowed in recent days from its peak last month. The pace of vaccinations has recently picked up following a slow rollout marked by fragmented communication between federal authorities and vaccination sites, distribution bottlenecks and other issues.

Worldwide, Covid-19 has infected more than 110 million people and killed more than 2.4 million.