- US public-health experts aren't sure when Americans who've survived the coronavirus will be eligible for a vaccine.
- Some leading trials — including Moderna's — excluded anyone with a history of coronavirus infection, so researchers don't yet know how a vaccine would affect those people.
- Without that data, experts say, it's unwise to inoculate people who were previously infected, particularly if they have lingering symptoms.
- Visit Business Insider's homepage for more stories.
Unlike many Americans, Signe Redfield wasn't comforted by the news that a coronavirus vaccine could soon reach the public.
A roboticist at the Naval Research Laboratory in Washington, DC, Redfield has had COVID-19 symptoms since March. Her fatigue lasted around seven months, her mind continues to feel foggy, and she has trouble sleeping. But people like her, who already got sick, could be among the last in line for vaccines. And researchers still don't know what effects the shots might have on them.
In October, an independent group of experts convened by the National Academy of Sciences issued recommendations about the order in which a vaccine should be made available to various groups. The guidelines, which are expected to be adopted by the US government, suggest healthcare workers should get immunized first, followed by elderly people in nursing homes. But there's no advice for people who were previously infected.
"Many unknowns remain regarding the safety and efficacy of the vaccines in certain populations," the experts wrote. Those populations, they said, include "individuals previously infected with COVID-19."
Indeed, Moderna and the Sanofi-GlaxoSmithKline partnership excluded people from their trials who tested positive for the virus in diagnostic or antibody tests. Novavax, too, did not accept anyone who'd been diagnosed or had known exposure. That's primarily because those people may have already developed a robust antibody response and could skew the data.
But the omission means researchers have no idea whether a vaccine would be safe or effective for people who've had COVID-19.
"It's hard for me to have confidence that it's going to be safe for our population," Redfield told Business Insider, referring specifically to those with lingering symptoms. "I am going to be more concerned about exposing my body to another immune challenge."
But individuals who've gotten the coronavirus may need to get vaccinated eventually, given that scientists don't know how long immunity lasts.
Should people who've had COVID-19 get vaccines?
Pfizer and Moderna both announced positive results from their phase-three trials this month: Pfizer's vaccine was found to be 95% effective in preventing COVID-19, while Moderna's was found to be 94.5%. Experts now anticipate that Americans could have widespread access to a vaccine by spring or summer 2021.
But more than 10 million people in the US face a dilemma about whether to get these shots — and don't know whether they're eligible at all — since about 3% of the population has now survived the coronavirus.
"We want to look at vaccinating patients who have not been infected with COVID who are susceptible," Todd Ellerin, director of infectious diseases at South Shore Health in Massachusetts, told Business Insider. "The post-COVID patients are not going to be your first, second, third, or fourth tier of groups that you're going to look at to want to vaccinate."
There's also a large group of people who got the virus, but weren't aware of it — either because they couldn't get tested or because they were asymptomatic carriers. They'll likely seek out a vaccine.
"Because of the lack of testing, there are many, many people who have had COVID-19 who don't know it," Natalie Lambert, an associate professor of medicine at Indiana University, told Business Insider. "We need to investigate some of these things, along with seeing how people who have not had COVID could be protected by a vaccine."
How long does immunity last?
Immunity to the coronavirus is still one of the most critical, unsolved mysteries of the pandemic. An October study found that COVID-19 patients had a stable antibody reponse for at least five months. And a recent study from The Rockefeller University (though still awaiting peer review) found that people have enough memory cells to fend off the virus for at least eight months. If memory cells wane slowly, immunity could last for several years.
However, there have been several confirmed instances of people getting coronavirus infections twice. So eventually, people who were previously infected may still require a shot to boost their immune response.
"Survivors will likely need a booster at some point," Ellerin said.
But it's unwise to inoculate these individuals without more safety data, he added.
"We have to keep our eye on the prize right now," Ellerin said. "Of course patients can get COVID more than once, so I'm not trying to tell you that they'll be excluded from this down the road, but we have a lot more to learn."
Long-haul patients face even more worries about getting a shot
Redfield is considered a coronavirus long-hauler: a patient whose symptoms last three weeks or more.
Researchers still aren't sure what portion of people develop these long-term complications, but a July report from the Centers for Disease Control and Prevention found that around one-third of coronavirus patients surveyed had not recovered after two to three weeks. An August study estimated that one in 10 coronavirus patients experience prolonged illness.
Lambert said long-haulers have almost certainly been excluded from vaccine studies so far due to ethical issues.
"It'd be hard to engage a long-hauler in that study if they're having ongoing health problems," she said. "Ethically there'd be big problems with having them take a vaccine, if you're worried about those effects. But at the same time, we need to get those answers before we can really recommend that long-haulers or people who had COVID should do certain things or even avoid certain things."
For people with long-lasting symptoms, it's possible that a vaccine could intensify an already aggressive immune response — which, for many of them, has led to fatigue, muscle aches, trouble breathing, heart palpitations, or difficulty concentrating or sleeping.
Redfield said she probably won't be comfortable getting a vaccine until researchers have time to learn more about long-haulers. She estimates that could take another year.
By then, she said, "I would have more confidence that if there was a bad interaction, they would be able to treat it properly."
Some people with coronavirus antibodies have slipped into trials
Since Moderna did not include people who already had COVID-19 in its clinical trials, the company may have to run more trials to see whether its shot is safe and effective for that group. Pfizer, though, may already have enough data to figure out the answer. The company's phase-two and phase-three clinical trials didn't exclude people who'd been sick before.
On Wednesday, Pfizer said data from its phase-three trial showed that its vaccine was also 95% effective in participants with a prior coronavirus infection.
Ellerin said further investigation of those results could prove useful, since the sample size is likely small.
"It will be important to look at that group to see: how did they respond?" he said, but added, "this is not the target group that we're looking at first."