We Need a Reality Check on the Coronavirus Vaccine
The robustness and duration of immunity to Covid-19 is unknown, and vaccines are really hard to create
Anyone expecting a Covid-19 vaccine will eradicate coronavirus from our lives anytime soon or that our collective immunity will thwart the spread should, for now, keep up those physical-distancing efforts until science suggests otherwise.
Antibody tests to determine whether a person who has been infected with the coronavirus has some level of immunity and might, therefore, be able to return to work should be available in “a week or so,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease (NIAID), said April 10 on CNN.
But how much immunity people will have, and how long it might last, remains unknown. Meanwhile, a vaccine could still take many months to develop and distribute, experts say, and there is no guarantee that one is possible.
“Because this coronavirus is highly infectious and causes serious symptoms, that tends to really crank up the body’s immune response to it, and so that means it’s less likely to re-infect somebody.”
“There are a lot of very smart people working very hard to come up with a vaccine” and develop the infrastructure to mass-produce it quickly, says Yonatan Grad, MD, an assistant professor of immunology and infectious diseases at Harvard T.H. Chan School of Public Health. It’s “likely” one will be developed, he says. “But it’s not a given.”
After decades of effort, there’s still no vaccine for HIV, Grad points out. And while vaccines have been developed for many other virus types from mumps to the flu, nobody’s figured one out for the common cold, which vexes researchers in part because it can be caused by multiple coronaviruses and some 160 different rhinoviruses.
The unpredictable curveball of immunity
When recovering from a viral infection, people typically develop some level of immunity, protecting them from reinfection. The body reacts to a virus by creating antibodies, protein structures that float through the bloodstream and act as catcher’s mitts for that particular virus, explains virologist Andrea Amalfitano, DO, dean of the College of Osteopathic Medicine at Michigan State University.
Think of the virus as the ball, Amalfitano says. Like a bad pitch that might otherwise get past a catcher, a good glove can help stop viruses from getting into the cells of your lungs or intestines or other organs where the infection would do its damage. Immunity to a given virus depends on how well the glove fits around the ball, how many gloves you have, and how long they stay in your bloodstream.
There’s an unpredictable curveball in the equation, however: The number of antibodies you need in your bloodstream to provide immunity varies from one virus to another. “We just don’t know yet what that number is for Covid-19 because it’s just so early in the game,” Amalfitano says.
The strength of a human immune response is dependent in part on Darwinian evolution.
“Assessing the presence of antibodies is not necessarily the same thing as assessing immunity.”
“Because this coronavirus is highly infectious and causes serious symptoms, that tends to really crank up the body’s immune response to it, and so that means it’s less likely to reinfect somebody,” Amalfitano tells Elemental. On the other hand, viruses that cause a relatively harmless disease like the common cold don’t trigger as robust of an immune response, and people don’t tend to become immune to them. This is one reason why they continue circulating and making people sick.
“Their evolution allows them to propagate because they’ve found that niche,” he says. Ebola is the opposite. “Its biology is so aggressive, it just kills the host before it has a chance to move on.”
But SARS-CoV-2, the coronavirus that causes Covid-19, has caused a dizzying array of reactions in people, from no symptoms to mild symptoms to rapid decline in severe cases and death. It infects and inflames the lungs, sometimes the gut, and maybe even the brain. The tests that Fauci promises won’t reveal whether severe cases create a more robust immune response than mild cases, nor how long any Covid-19 immunity might last. “Assessing the presence of antibodies is not necessarily the same thing as assessing immunity,” Grad says.
And over time, the virus is likely to change. It doesn’t have to mutate into a whole new strain to render an immunity less effective, Grad explains. The parts of the virus to which we develop an immune response need only change in relatively minor ways to do the trick. These are called antigenic changes, and they explain why the flu vaccine has to be reengineered every year.
Only time will tell the rate of antigenic change for SARS-CoV-2, Grad says.
Vaccines are hard to make
The immune system responds to an effective vaccine in much the same way it reacts to an infecting virus, generating a bunch of specialized catcher’s mitts but without making a person actually sick. It’s likely a vaccine will be developed for Covid-19, says Amalfitano, who has been involved in efforts to create vaccines for the flu and HIV, but the process is riddled with hurdles and may well take another nine to 12 months. Consider the annual flu vaccine, which takes several months to recreate before every season. Even though scientists are familiar with an ever-evolving strain of influenza and have developed reliable methods to produce the vaccine, they have to reengineer it, test its effectiveness, and then produce it on a mass scale.
Researchers are starting from scratch in the effort to create a vaccine against SARS-CoV-2. Even if one proves effective and safe in small tests — in rodents or humans — it will likely take months to scale production up because every vaccine requires a unique production technique.
“It just takes time to scale this up and there are no guarantees,” Amalfitano says. Along the way, expect to hear of promising vaccine candidates that never materialize into the real deal, he says.
Herd immunity vs. second waves
In the nearer term, Fauci and other health officials worry about relaxing stay-at-home orders and physical distancing measures too soon, potentially causing a second wave of outbreaks.
Yet as the virus runs unchecked through a population it might be creating some level of herd immunity, collective protection that, like a vaccine, can slow or stop further outbreaks.
Health officials do not wish to foster herd immunity, given the number of deaths that might come with it. But at the same time, it’s possible that herd immunity is already happening to some extent in some places. Experts simply have no clue how many people have actually had Covid-19 and never knew it or weren’t tested.
So as tests detecting coronavirus antibodies are deployed and people presumably return to work, a big question looms: Is Covid-19 causing a strong immune response in enough people to create some level of herd immunity and prevent a fresh wave of outbreaks and possibly render a vaccine less urgent?
“That’s the million-dollar question,” Amalfitano says. “If those people all of a sudden come down again with Covid-19, I think we’ll have our answer.”