Will Delta be the last major variant?
There are three ways the coronavirus could continue to evolve, as Dhruv Khullar, a physician and an assistant professor at Weill Cornell Medical College, explained in The New Yorker:
In the first scenario, the virus simply fails to find a way to escape vaccine-generated immunity. Some scientists think that’s a plausible outcome: Many viruses — measles, mumps, polio and smallpox among them — have never beaten the vaccines created for them.
In the second scenario, the virus manages to partly evade the vaccines’ protections, but at a price (a decline in infectiousness or lethality, for example). This scenario occurred with H.I.V. in the 1990s, when the virus developed a mutation that increased its resistance to an antiviral drug but lowered its rate of replication inside the body.
In the third scenario, the most concerning, the virus manages to find a way around vaccine-generated immunity while maintaining — or even gaining — transmissibility or lethality.
Many scientists say that there are biological and epidemiological constraints on how fearsome the coronavirus can become: If it grows too transmissible or too lethal, “it’ll burn itself out,” Nash Rochman, who studies computational genomics at the National Institutes of Health, told Vox.
But no one knows for certain how much evolutionary runway the virus has left. “There are certainly limits,” Kristian Andersen, an infectious-disease researcher at the Scripps Research Institute, told Khullar. “We just have no idea where they are.”
But even if another concerning variant emerges, it won’t necessarily spell disaster. As John M. Barry, a historian and the author of “The Great Influenza,” noted in The Washington Post, all five flu pandemics we have detailed information about developed more virulent variants before petering out. And if the coronavirus circumvents the vaccines, it will happen gradually, he said, leaving time for vaccine producers to make the necessary adjustments.
“Whether we need booster shots with existing vaccines or not, we will eventually require updated vaccines targeted against the latest variant, just as we do each year for influenza,” he wrote. “Even if Delta is the worst variant we see, the virus will continue to mutate. As with influenza, the goal is to develop a vaccine that protects against all variants.”
If the coronavirus isn’t going away, how do we live with it?
Eventually, experts say, when everyone has been vaccinated or infected, the coronavirus will become endemic: Outbreaks will be rarer and smaller, and hospitalizations and deaths will decline. “There will be a time in the future when life is like it was two years ago: You run up to someone, give them a hug, get an infection, go through half a box of tissues and move on with your life,” Jennie Lavine, an infectious-disease researcher at Emory University, told Yong. “That’s where we’re headed, but we’re not there yet.”
How long it will take to get there remains an open question. In the United States, it’s possible that the Delta variant will soon run out of unvaccinated people to infect, as some speculate has occurred in Britain.