...The nightmare scenario: the virus mutates into a variant that renders current vaccines weakened or obsolete before the rollout reaches the 150 million or so people needed to achieve herd immunity, which would halt the virus in its tracks.
If we're really unlucky, mutated versions of SARS-CoV-2 already circulating are enough to cause such a setback. That's what some studies suggest—though these are preliminary, and it could take weeks or months of collecting patient data to clearly demonstrate what any particular variant is doing. "All indications are that these variants of the virus could be a significant challenge to the vaccine," says Michael Osterholm, the straight-talking infectious disease expert at the University of Minnesota who was a key member of
Joe Biden's pre-inauguration COVID advisory board. "Without a doubt that's potentially the most overwhelming problem we face."...
Dangerous mutations are popping up left and right in part because the COVID-19 case rate is so high. When the virus enters a person's bloodstream, it creates billions of copies of itself in the victim's cells. The essence of mutation is that some of those copies aren't quite identical to the original. In the vast majority of cases, these random mutations have little effect on the virus, or even reduce its ability to infect and sicken. But given enough opportunities, a copy of the virus is bound to end up changed in a way that makes it more transmissible, deadlier, or able to beat the vaccine—or, in the worst-case scenario, all three.
With more than 25 million known cases in the U.S. and 100 million worldwide, the virus has a vast playground for trying new mutations. The more infected people, the more likely that a vaccine-defeating virus will pop up sometime soon...
Scientists' biggest concern is the emergence of variants that can render the vaccine less effective. The first crop of those variants is already here: one first turned up in South Africa, another in Brazil, and a third in Washington State. The two vaccines approved in the U.S.—from Pfizer and Moderna—work by stimulating the body's immune system to produce antibodies that primarily look for the spike protein on the virus. The altered spike proteins in the South Africa, Brazil and Washington variants seem to make them as much as ten times less recognizable to those antibodies, according to lab studies that have been posted, though not yet peer-reviewed. (These variants can probably also defeat the monoclonal-antibody therapies that have proven effective in reducing the severity of illness in COVID patients and may lead to false negative results in testing.) Novavax reported that its vaccine proved 90 percent effective in U.K. tests but only 50 percent in South Africa, which suggests it may be less effective against the variant that arose there. (Scientists cautioned that the data was preliminary and the South African study was too small to draw firm conclusions.)
Immune responses are complex and not fully understood. It's possible that contrary to the lab findings many or even most vaccinated people will end up with a variety of antibodies and other immune defenses, some of which won't be fooled by the mutations of the spike protein that have emerged so far. That's a reasonable expectation, notes Sharone Green, a physician and researcher specializing in infectious disease at the University of Massachusetts Medical School. "The variants are concerning, but so far there's nothing in the peer-reviewed literature that says they make the vaccine less effective," she says.
Even if we luck out with the variants that have already arisen, more are inevitably on the way. "We can expect strains that have further mutated into something that better evades the immune response from the vaccine," says Anthony Harris, a physician who heads clinical operations at Workcare, a company that helps organizations reduce employee infection risks. The annual flu vaccine, for example, is typically only 50-to-70-percent effective in large part because the influenza viruses are so good at continually and rapidly mutating. The COVID-19 virus is pretty good at mutating, too: The U.K. and South African variants, both of which have reached the U.S., carry eight and nine mutations, respectively, to the spike protein. While there are no specific number or type of mutations to the protein needed to defeat the vaccine, any combination of mutations to the protein raises the threat.
The vaccines can win this race, even with resistant variants already in circulation. To do so, it will have to bring case rates way down before vaccine-defeating variants have a chance to spread widely. If the case rates drop enough, then limited outbreaks of vaccine-resistant variants could be controlled with quarantines, lockdowns, and other standard containment efforts. In addition, low case rates provide the virus with fewer opportunities to develop additional mutations that could cause even bigger problems.
Vaccine developers, meanwhile, would get the time they need to come up with versions that are effective against the variants—a process that might take as little as three months from start to rollout, if the tweaks to the vaccine are minor enough to win
FDA approval without large clinical trials. "We can keep adapting the vaccine to chase the virus as it mutates," says Osterholm. Pfizer and Moderna have already announced fast-moving efforts to produce booster shots for vaccinated people that will improve their immunity to the known variants, and they'd likely be able to do the same for future variants. There are also proposals to deliver a third shot of the existing vaccines, which might raise resistance enough to defeat the variants.
But if virus-evading mutations get around more quickly than the initial vaccines do, we'll essentially have to start from scratch in vaccinating the population, likely crushing hopes of defeating the pandemic this year....
All these challenges threaten to indefinitely delay hitting herd immunity—the point at which a large-enough percentage of the population has achieved immunity, whether through vaccine or infection, to rob the virus of enough potential victims to continue spreading widely. Herd immunity would essentially mark the end of the crisis....
If we don't get to herd immunity, or close to it, by late fall, we face the possibility of a significant third wave of the pandemic. That's what happened in the influenza pandemic of 1918, which returned with a vengeance in 1919 to kill millions more around the world...
The bottom line: There's a good chance the pandemic will be with us into 2022. If so, the virus will by then have had plenty of opportunity to evolve into strains that the current vaccine can't stop. But new versions of the vaccines adapted to these strains will be coming out. In addition, much of the population will likely have started to build up broader natural or vaccine-induced immunity to the virus that will at least lessen the impact of the new strains. Ultimately, COVID-19 is probably destined to end up much like the common cold or the flu. That's typically how pandemics wind down. "We'll all get reimmunized every year, problem solved," says Rosenberg....
herd immunity.
