Research shows both coronavirus infection and vaccination offers immunity that can protect people from getting sick again. But by how much and for how long remains unclear — a scientific gap that only time could fill.
Regardless of how immunity is acquired, there’s no telling whose bodies will or won’t create effective antibodies, and why they last longer for some than others; doctors speculate age or certain medical conditions might play a role.
It also doesn’t help that the testing shortage that plagued the nation at the beginning of the pandemic will forever shield researchers from understanding the true impact of COVID-19.
The Centers for Disease Control and Prevention estimates that between February 2020 and March 2021, there were about 114.6 million total coronavirus infections in the U.S. That’s about 81.1 million more cases than are confirmed as of June 17.
While people can gain immunity from both infection and vaccination, antibodies created from both routes target different parts of the virus, which leads to variations in the quality of protection.
It’s like a coin flip: risk contracting COVID-19 — and potentially becoming a long-hauler — or getting vaccinated. Some argue the final outcome is similar, but one is far more dangerous than the other.
Here’s what the latest data show about immunity from prior infection and vaccines.
There are certain illnesses in which infection can offer more protection than a vaccine.
For example, coming down with measles or mumps is said to confer lifelong immunity to the virus, but some people who get the vaccine may still get infected, although the shots still limit and prevent the spread of outbreaks.
But if the novel coronavirus is anything like others in the coronavirus family, like the Middle East Respiratory Syndrome (MERS), then permanent protection after infection is unlikely.
Studies offer some positive clues, however.
Research published in February found that coronavirus patients gained “substantial immune memory” that involved all four major parts of the immune system: memory B cells, antibodies, memory CD4+ T cells and memory CD8+ T cells.
This protection lasted about six months after infection in most people, but for some, it remained for up to eight months, suggesting it could last even longer in some cases.
Separate research posted in April showed a history of COVID-19 among U.K. patients was associated with an 84% lower risk of reinfection for about seven months after testing positive.
Another non-peer reviewed study published in June found that over five months, 1,359 American health care workers who previously had COVID-19 and didn’t get vaccinated stayed clear of reinfection. The Cleveland Clinic researchers said, in the context of a short supply of vaccines globally, “a practical and useful message would be to consider symptomatic COVID-19 to be as good as having received a vaccine,” adding that people who’ve had the coronavirus “are unlikely to benefit from COVID-19 vaccination.”
While scientists cannot predict who will develop natural immunity, evidence shows people who had severe COVID-19 are more likely to develop a stronger immune response than those who had milder forms of the disease.
It’s also true that research shows COVID-19 vaccines offer protection against reinfection, although “breakthrough cases” can occur because no vaccine is 100% effective.
However, studies have found vaccine-derived antibodies are more robust compared to those from natural infection — and the job is done without causing illness or other long-term complications often brought on by the disease.
Two doctors from Italy compared the process of infection and vaccination in relation to variants to the plot of an action movie.
It “begins with a character (the virus) running freely across the globe, eluding capture until being finally sent to jail (built by natural immunity). However, if this prison is not secure enough, the virus could escape, aided by certain mutations,” Dr. Emanuele Andreano and Dr. Rino Rappuoli of the Monoclonal Antibody Discovery Lab, wrote in Nature. “Vaccine-induced immunity… should help ensure those escape routes are securely closed.”
An April study that has not been peer-reviewed found that two doses of either the Pfizer or Moderna vaccines offered 10 times higher levels of antibodies compared to those developed after natural infection.
Another April paper showed that people who were previously infected with the coronavirus experienced significant boosts in their preexisting antibodies after two doses of the Pfizer vaccine, which also offered protection against coronavirus variants.
“Vaccines actually, at least with regard to SARS-CoV-2, can do better than nature. … They are better than the traditional response you get from natural infection,” White House chief medical adviser Dr. Anthony Fauci said during a COVID-19 briefing in May.
Exactly why vaccines appear to generate more robust immunity than natural infection remains unclear, but Dr. Sabra Klein, a virologist and professor of immunology at Johns Hopkins Bloomberg School of Public Health, said infection and vaccination work in different ways.
“The immune system of people who have been infected has been trained to target all these different parts of the virus called antigens. You’d think that would provide the strongest immunity, but it doesn’t,” Klein said. “The Pfizer or Moderna vaccines target just the spike protein — the part of the virus that is essential for invading cells.
“It’s like a big red button sitting on the surface of the virus. It’s really sticking out there, and it’s what our immune system sees most easily,” she continued. “By focusing on this one big antigen, it’s like you’re making our immune system put blinders on and only be able to see that one piece of the virus.”
In other words, vaccines work to strengthen immune responses gained during natural infection; that’s why health experts advise people who’ve had COVID-19 to still get vaccinated.
“There’s nothing deleterious about getting a boost to an immune response that you’ve had before,” Dr. Marion Pepper, an immunologist at the University of Washington in Seattle, told The New York Times. “You could get an actually even better immune response by boosting whatever immunity you had from the first infection by a vaccine.”