Transmission of coronavirus among vaccinated people could increase the risk of an even more dangerous variant

The coronavirus could be “a few potentially distant mutations” from evolving to a variant that can elude existing COVID-19 vaccines, CDC director Rochelle Walensky said on Tuesday.

According to a study published Friday in the journal Scientific Reports, people vaccinated – counterintuitively – play a key role in this risk.

The best way to stop coronavirus deaths and serious illnesses is to roll out vaccines quickly. However, the researchers concluded that the likelihood of emergence of a vaccine-resistant strain is highest in a scenario that combines three conditions: First, a large portion of a population is vaccinated, but not everyone. Second, there are a lot of viruses around. And third, there are no measures in place to curb the potential viral transmission of those vaccinated. Seems familiar?

Prior to the rise of Delta, which is now responsible for more than 80% of coronavirus cases in the United States, this situation was not of concern as research suggested that those vaccinated were not likely to transmit other versions of the virus. But according to a CDC study released Friday, people who have been vaccinated can transmit the Delta variant just as easily as those who are not.

This could help explain the recent increase in cases in the United States: Over the past month, the seven-day average of daily new cases in the country has more than quintupled: from 12,263 on June 29 to 71,621 on Thursday.

The researchers concluded that, in an environment where Delta spreads among all people – regardless of vaccination status – it is imperative to get more people vaccinated immediately to prevent the emergence of a new vaccine-resistant variant.

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“Evolving arms race”

The researchers created a mathematical model that predicted which conditions are associated with the highest risk of emerging new variants that may escape vaccines.

They found that if a large number of people are vaccinated but many unvaccinated people remain, a variant that can escape or partially escape the immune defenses induced by the vaccine has a competitive advantage over other versions of the virus. So over time, these less adapted strains – which cannot infect vaccinated hosts – die off, leaving vaccine-resistant strains to dominate the viral landscape. Then, if viral transmission is left unchecked – a lot of people party without a mask, let’s say – these newly dominant variants can easily spread and evolve further.

“This means that the vaccine-resistant strain is spreading faster in the population at a time when most people are vaccinated,” said Simon Rella of the Austrian Institute of Science and Technology, who worked on the study, in an online briefing, CNN reported.

Rella and colleagues wrote that this dynamic could lead to “vaccine development catching up in the evolutionary arms race against new strains.”

Partially vaccinated people could unwittingly teach the virus to bypass our defenses

Virologists call variants of a virus that escape the immune defenses induced by a vaccine or disease “escape mutants.” So far, no variant of the coronavirus can completely escape COVID-19 vaccines.

But the reason a future variant might do this is because the injections all target the coronavirus spike protein – the sharp, crown-like bumps on the surface of the virus that help it invade our cells. If several significant mutations sufficiently modify the characteristics of this protein, the antibodies might not be able to recognize or properly fight this new variant.

Infections in partially vaccinated people increase the risk of a game-changing mutation because it takes time for the body to develop the antibodies, T cells, and B cells that fight the virus, and our immune response increases dramatically afterwards. the second dose. So if someone is infected in the meantime, it gives the virus a glimpse of what they’re up against. With Delta, research shows that a single injection of the Pfizer or AstraZeneca vaccines is only 33.5% effective against the variant.

“Not having immunized all of us creates a perfect circumstance for the appearance of variants that are escape mutants,” James Hildreth, immunologist and president of Meharry Medical College, told Insider in April. “If there are people who have a low level of immunity, in a way, it’s almost worse than having no immunity at all.”

Hildreth added that partial immunity “can actually lead to the formation and presence of viruses which do not bind to the antibody.”

“They are going to take over and be the ones that are passed on,” he said.

The new study supports the CDC’s recent guideline that vaccinated people should wear masks in high transmission areas. Hildreth is fully vaccinated but said that didn’t stop her from putting on his mask when he left the house.

“I don’t want to become a vector and unintentionally pass the virus on to others, which is another reason I wear the mask,” he said.

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