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In the immediate aftermath of last month’s news of the surprising results of Pfizer and Moderna’s Covid-19 experimental vaccines, Senator Rand Paul tweeted a provocative comparison.
The new vaccines were 90% and 94.5% effective, Paul said. But “naturally acquired” Covid-19 was even better, at 99.9982%, he claimed.
Paul, R-Ky., Is one of many people who, fed up with lockdowns and economic losses, have extolled the benefits of contracting the coronavirus. The senator was diagnosed with the disease this year and has argued that surviving a Covid-19 attack confers greater protection and presents fewer risks than getting vaccinated.
The problem with that logic is that it’s difficult to predict who will survive an infection unscathed, said Jennifer Gommerman, an immunologist at the University of Toronto. Given all the unknowns, such as a region’s hospitable capacity or the strength of a person’s immune response, choosing the disease over the vaccine is “a very bad decision,” he said.
The main advantage of a vaccine is that it is predictable and safe, he said. “It has been optimally designed to generate an effective immune response.”
But what do we know about how immunity from a previous infection compares to the protection provided by new vaccines? What if you have already had Covid-19? Is it safe to get vaccinated? We asked the experts to evaluate the latest evidence.
What produces a stronger immune response: a natural infection or a vaccine?
The short answer: we don’t know. But Covid-19 vaccines have predictably prevented disease and are a much safer bet, experts said.
Vaccines for some pathogens, such as pneumococcal bacteria, induce better immunity than natural infection. Preliminary evidence suggests that Covid-19 vaccines may fall into this category. Volunteers who received the Moderna vaccine had more antibodies, a marker of immune response, in their blood than people who had been ill with Covid-19.
In other cases, however, a natural infection is more powerful than a vaccine. For example, having mumps, which can cause infertility in men, builds lifelong immunity, but some people who have received one or two doses of the vaccine still get the disease.
For Paul’s point: Fortunately, the natural immunity to coronavirus is quite strong. The vast majority of infected people produce at least some antibodies and immune cells that can fight infection. And the evidence so far suggests that this protection will persist for years, preventing serious illness, if not re-infection.
But there is a “massive dynamic range” in that immune response, with a 200-fold difference in antibody levels.
In people who are mildly ill, the immune protection that can prevent a second infection can diminish within a few months. “Those people may benefit more from the vaccine than others,” said Bill Hanage, an epidemiologist at Harvard’s TH Chan School of Public Health.
The diversity in the immune response of natural infection could be due to differences in the amount of virus to which the person was exposed.
With a vaccine, everyone receives the same dose. “We know the dose that is being administered and we know that that dose is effective in eliciting an immune response,” Gommerman said. “So that becomes a variable that is taken off the table when he receives the vaccine.”
I am young, healthy and at low risk for Covid-19. Why not take a chance on it instead of getting a hasty vaccination?
The experts were unanimous in their answer: Covid-19 is by far the most dangerous option.
“It’s clear that one is less of a problem for the body to recover from than the other; there is more risk with natural infection,” said Marion Pepper, an immunologist at the University of Washington in Seattle.
People who are obese or suffering from diseases such as diabetes are particularly susceptible to severe cases of Covid-19. On average, the virus appears to be less risky for younger people, and women tend to do better than men. But beyond those broad generalizations, doctors don’t know why some people become seriously ill and die while others have no symptoms.
For example, people who harbor certain mutations in immune genes are more susceptible to the disease, several studies have shown. “So there is a risk factor that has nothing to do with age,” Gommerman said.
In a study of more than 3,000 people, ages 18 to 34, who were hospitalized for Covid-19, 20% required intensive care and 3% died.
“It’s true that most people are not going to be hospitalized, most people are not going to enter the intensive care unit or die,” said Dr. Yvonne Maldonado, who represents the American Academy of Pediatrics at the meetings of the Advisory Committee on Immunization Practices.
But “no one is immune from serious diseases,” he said. And even if people are not at high risk for Covid-19, their friends or family could be.
Up to one in three people recovering from Covid-19 have chronic complaints, including exhaustion and a racing heart, for months afterward. This includes people under the age of 35 with no prior health problems. Some Covid-19 survivors also show worrying signs that their body has turned in on itself, with symptoms similar to those of lupus and rheumatoid arthritis.
Covid-19 vaccines, by contrast, carry a little-known risk. They have been tested in tens of thousands of people without serious side effects, at least so far. “Once you start vaccinating millions, you may encounter very, very rare events,” Hanage said. “But we have to know that they are very, very rare and much rarer than the adverse events associated with natural infection.”
He had Covid-19. Is it safe for me to get a vaccine? If so, when can I get one?
It is safe, and probably even beneficial, for anyone who has had Covid-19 to receive the vaccine at some point, experts said.
“There is nothing harmful about getting a boost from an immune response that you’ve had before,” said Pepper. “You could get an even better immune response by boosting the immunity you had from the first infection with a vaccine.”
In fact, in a meeting on Wednesday, Dr. Moncef Slaoui, a senior advisor to Operation Warp Speed, said that up to 10% of participants in clinical trials of the vaccines had been infected with the virus without knowing it. Their immune responses to the vaccine are being tested, he said.
If you have already had Covid-19, you can afford to wait a while to get the vaccine.
Studies by Pepper’s team and others have shown that the immune response evolves during the first few months after infection, but everyone who has had Covid-19 has some level of protection during that time.
“We didn’t see anybody who didn’t develop some kind of immune response,” he said. “I don’t think these people should rush to get vaccinated in the same way that highly susceptible people do.”
The ACIP, which makes recommendations to the Centers for Disease Control and Prevention on vaccine distribution, said at a meeting Wednesday that people who had not been infected should take priority over those who contracted the virus in the past 90. days.
“At some point we will have to find out if 90 days is the correct number,” Maldonado said. But for now, “people who have evidence of infection recently probably shouldn’t get vaccinated in the front row because there is very little vaccine available.”
