The unchecked circulation of the coronavirus in countries lacking vaccines raises the risk that a coronavirus variant able to evade vaccines will find its way to the United States, infectious disease experts say.
The U.S. is expected to be highly protected from further mass outbreaks as the vaccination campaign proceeds, but the spread of such variants could pose a threat to vulnerable people.
“I think the risk is very high that we will see more mutant variants enter into our population and begin to cause another wave of infections, no different than what the [United Kingdom] variant has done,” said Dr. Manoj Jain, an infectious disease physician at the Rollins School of Public Health at Emory University. “I think the variants from Brazil or from India will do something very similar in the next six to nine months.”
Rising vaccinations in the U.S. and other wealthy countries will soon slow the circulation of the coronavirus. But that progress could be undone by poorer nations with low rates of vaccination. In those nations, the virus can still more easily circulate, possibly mutating in a way that can enable it to evade vaccines.
If that mutated form of the virus makes its way to the U.S. and begins spreading, even people who are vaccinated will be infected. And while it is unlikely that those who are vaccinated will get seriously ill, they can spread it to those who are still vulnerable.
That type of mutated virus may have already developed in India. The India variant of the coronavirus, known as B.1.167, has two mutations on its spike proteins, the parts of a virus that enable it to attach to and invade cells in the human body. Those two mutations enable it to evade the antibodies that are generated by coronavirus vaccines.
Thus far, B.1.167 has been found in about 10% of cases in India and is part of the reason that the country is currently facing a surge that is overwhelming its healthcare system.
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There are many reasons why poorer countries can generate coronavirus mutations.
“Developing countries are challenged by population density, with lots of people in urban areas,” said Jain. “That makes it easier for the virus to spread.”
Another reason that poorer countries can be breeding grounds for mutations in the coronavirus is that they often have limited resources for medical care. The current surge in India is stretching that nation’s healthcare system is stretched to the breaking point. Hospitals are desperate for more oxygen and are turning patients away.
Dr. Jeremy Kamil, professor of microbiology and immunology at the Health Sciences Center at Louisiana State University, Shreveport, said that places where HIV infection is common, such as Africa, pose an added risk.
“The big risk comes from an immunocompromised person, like one who has HIV,” Kamil said. “When the virus gets into an immune-compromised person, they may not die from it, they may recover, but the virus will linger in their body longer than it would in a normal person.”
The longer the virus lingers, the more time it has to develop mutations that can evade antibodies.
Finally, many poorer countries have very low rates of vaccination. This means they are far from herd immunity, in which a sufficient percentage of the population is inoculated, thereby making it much more difficult for the coronavirus to mutate. Thus far, barely 1% of India has been vaccinated. Of the countries reporting data in Africa, most have vaccinated less than 1%.
Officials in the U.S. and other wealthy nations have focused on vaccinating their own populations first. But Kamil said it is in the U.S.’s long-term interest to begin putting more focus on poorer nations.
“We are going to reap economic dividends by helping the rest of the world get vaccinated,” Kamil said.
However, the risk of a coronavirus variant depends not only on what happens abroad, but also what occurs in the U.S.
The risk of facing another surge is dependent, in part, on how many people in the U.S. get a vaccine. People who are vaccinated are much less likely to get a severe case of COVID-19, be hospitalized, or die.
The vaccine generates responses from two parts of the immune system: B-cells and T-cells. B-cells create the antibodies that prevent the virus from infecting cells by attacking the spike proteins. T-cells are primed by a vaccine to recognize when a virus has invaded a cell and then remove that cell from the body.
Research shows that while a coronavirus with spike protein mutations can evade antibodies, it is unlikely to avoid the T-cell response. Yet, since mutations can evade antibodies, people who are vaccinated can still carry the coronavirus long enough to infect others. That includes people who have not been vaccinated or people who have been but have weak immune systems. If there are still enough of them in the U.S., then a variant can cause a surge with more cases of severe cases of COVID-19 and hospitalizations.
The U.S. will also need to increase its genomic sequencing, testing that enables researchers to know if a particular case of COVID-19 is caused by the original strain or a variant.
“The lack of genomic sequencing infrastructure in the U.S. is a potentially a major setback to us controlling the virus,” said Jain.
Adequate genomic sequencing would help public officials know when a variant is spreading and when they need to take steps to isolate individuals with the variant and trace and contact people who have been in contact with those individuals.
At least 5% of COVID-19 samples need to be genomically sequenced to achieve an adequate statistical sample. Thus far, most states in the U.S. have sequenced less than 2%.
The biggest threat would be a variant that can evade not only antibodies but also T-cells. Such a variant could cause severe cases of COVID-19 for even vaccinated people. It is possible, but the risk is very small.
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“It is very unlikely, although there will be some person-to-person variability,” said Kamil. “It is very difficult for a virus to absolutely escape either arm of the immune system when it comes to antibodies or T-cells. And it is probably a little bit harder for it to escape T-cells.”
