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If I had COVID-19, should I take an antibody test?
It’s a good idea, Wherry said, but whether it’s practical is a different question.
“I think it’s useful to know whether or not you have antibodies, and that may be helpful in knowing whether your protection goes away,” he said. “I think a lot of institutions and businesses are thinking about whether or not to mandate vaccination. And if they do, will they use a documented previous COVID infection as evidence of being immune? So this is an important question.”
“Most people that previously had COVID will be protected. We don’t know for how long,” Wherry said. “Would it be valuable to check antibodies over time to know whether those antibodies have disappeared and use that as perhaps an indicator that now it’s time to get vaccinated? All really good questions. How you implement them in different settings, or even more broadly, from a public health standpoint, I think has to be factored in. It will be challenging to do so right now.”
There also are different kinds of antibody tests available, and they can be somewhat tricky to interpret because there are different ways of looking for the antibodies, Maragakis said.
“I would say right now there’s not a lot of reason for someone to go and get an antibody test unless you’re just curious,” she said. “I mean, that’s one reason, to see if you’ve been exposed in the past. But the recommendation is to get vaccinated, even if you’ve had a prior infection with COVID-19, because of that more robust, higher level of antibody response that most people get with vaccination as opposed to natural infection.”
How does getting one variant protect me from another?
When your immune system responds to one virus, it provides some degree of protection against similar viruses, Maragakis said. But the more different the viruses are, the more likely your immune system might not be able to recognize them, she said, and that’s why health experts are concerned about variants.
Studies show that the currently available COVID vaccines are effective against the current COVID variants.
A study published in July in the New England Journal of Medicine found that two doses of the Pfizer vaccine was 88% effective at preventing symptomatic disease from the delta variant, compared to about 95% for the original virus strain. Data from Israel estimated lower effectiveness against symptomatic disease, but said that the protection against severe illness remains high.
The concern, though, is that “the more the virus is allowed to circulate, the more variants may emerge and we may see a time that a variant escapes the currently available vaccine. And at that point, we would have to modify the vaccines and re-vaccinate people against the new variant,” Maragakis said.
Researchers can study the effectiveness of a previous infection against variants by taking antibodies from people who have had COVID-19 and testing their ability to neutralize the different variants in the laboratory.
Antibodies generated from natural infection and vaccination do respond to the delta variant reasonably well. It’s actually the beta variant, first identified in late 2020 in South Africa, that antibodies have had trouble neutralizing, Wherry said. The concern about the delta variant, though, is that the amount of virus that gets transmitted is much higher, making it more infectious.
“So let’s say that you needed a certain amount of antibodies to prevent a thousand viral particles from starting to infect your upper respiratory tract. So you’d be protected if all that’s been transmitted is a thousand particles,” Wherry said. “With the delta variant, we know that people are harboring a thousand-fold higher amounts of virus in their nasal passages when they get infected. So now you might be not transmitting a thousand viral particles, but actually a million viral particles, and you can overwhelm the antibody responses there.
“And so what that means,” Wherry added, “is that even if you’ve had the vaccine, even if you previously had COVID, even if you’re hearing that the vaccines are still working against delta, we need to be careful because delta is actually giving off more viral particles, meaning that all of us may still be, to some extent, a little bit susceptible.”
How long should I wait to get the vaccine after having COVID-19?
Right after an infection, the body’s immune response is at its peak, so it makes sense to wait several weeks before getting vaccinated, Maragakis said. She suggests about six weeks, or even up to 90 days. But you shouldn’t wait much longer than that, she said.
“We also know that immunity does wane after a natural infection, and people sometimes do get reinfected. And so it’s really a matter of waiting for several weeks, but not too long to get the vaccine,” Maragakis said.
Wherry said people who have had COVID-19 should consult with their physicians and make sure their symptoms have completely resolved. Getting a vaccine too soon could dampen its effectiveness, the experts said.
Right after getting COVID-19, the immune system is activated, and it responds to the viral pathogen and spike protein. If the person gets vaccinated too soon, the vaccine-mediated spike protein might get “lost” in the rest of the pathogen-mediated immune response, and fail to provide any additional boost to the immune response, Paragakis explained.
“We believe that giving the vaccination at least six weeks after acute infection gives the best chance for the vaccine to act as a ‘reminder’ to boost and stimulate a stronger and more durable immune response,” she said.