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In the United States, 17 million cases of Covid-19 have been reported, or about 5% of the population. Millions more have been infected and have not been tested or shown symptoms to begin with.
Vaccines are rolling out slowly – first to primary healthcare and those at high risk, and then, probably to other essential workers, followed by people 65 years of age and older and those with pre-existing illnesses.
But it’s reasonable to ask, given that there are well over 100 million people in these groups and there aren’t enough vaccines for them right away: people who have already had Covid -19 should they also be vaccinated?
After all, the body mounts an immune response to the virus during infection. In laboratory studies, scientists find that most people who contract the virus develop neutralizing antibodies against it. These antibodies are the proteins of the immune system that bind to viruses and make them harmless.
So a person who has had the virus has probably developed some level of immunity. Still, immunologists and vaccine experts say these people can – and perhaps should – get vaccinated anyway, if a vaccine is made available to them.
“If I personally had Covid, I would still like to be vaccinated,” says Alexander Sette, an immunologist at the La Jolla Institute of Immunology.
He and other experts in immunology and vaccines can explain why.
Why people who have had Covid-19 should still be vaccinated
The main reason everyone – whether or not they have had Covid-19 in the past – should be vaccinated is because different immune systems have responded to the virus very differently.
In general, says Sette, a body will mount a lasting immune response. “In fact, we’ve seen it persist for up to eight months,” he says. But this is only the case for 90% of people. “For 10% of people, they don’t seem to have a good immune response eight months later.”
There have been a few documented cases of re-infection, which suggests that in some people, the immunity that comes from a first infection is either weak or wanes over time (scientists are still not sure how bad the re-infection is. current). In general, scientists have told us that the more severe the first infection, the stronger the immune response.
The point is, “we have no way of telling,” he says, at least easily and practically, whether a once-infected person is in the 90% or the 10%. Not taking precautions like masking and social distancing, or avoiding a vaccine after an infection, he says, is like “driving a car where you’re 90% sure the car has brakes.”
This has been the story of the entire pandemic: the human body’s response to the SARS-CoV-2 virus that causes Covid-19 has been extremely variable. Some people have no symptoms. Some people end up dying from the infection. “Some develop very high levels of neutralizing antibodies and probably don’t need vaccines, while others develop undetectable levels of neutralizing antibodies,” says Akiko Iwasaki, immunobiology researcher at Yale in an email .
So quite simply: a vaccine helps to level out this variability. People whose immune system has not produced a robust response can catch up with those who have. According to Sette, there is less variability in people’s immune responses to Covid-19 vaccines than to natural infection.
And, again, people who have had Covid-19 can’t really assess their own level of immunity. Yes, a person could potentially have an antibody test, to see if there is any in their bloodstream.
But the immune system has many, many other components, from memory B cells that can be activated to produce antibodies in the future, to T cells, which kill and destroy infected cells. These are generally not tested. And even though an individual could be tested for all components of an immune response to SARS-CoV-2, it’s still unclear what all of this means for a second infection. Scientists still don’t understand the ‘correlate of protection’ for Covid-19. That is, what is the exact right mix of immune system cells for a particular person that would prevent them from being infected again?
Sette says it’s a “reasonable argument” to suggest that maybe people who have had Covid-19 should not be given priority in getting the vaccine, if the stock of it remains limited in the long term. But in practice, this argument could become problematic.
On the one hand: “It’s too difficult to operationalize pre-vaccination testing,” said Peter Hotez, vaccine expert and dean of the National School of Tropical Medicine at Baylor College, in an email. It would be tedious work to determine who could be immune to SARS-CoV-2 before vaccination. It could also be tedious to determine who was infected before vaccination.
Moreover, again, the information resulting from these tests may not be very useful in determining a person’s long-lasting immunity.
Vaccines are safe whether or not you have been infected
To sum up: “To be sure, I recommend getting vaccinated, even after your recovery from COVID, when vaccines become sufficiently available,” Iwasaki says.
It is still unclear what the vaccine would add besides a person’s natural immune response to the infection. Would a person who had a weak immune response to a natural infection have a stronger immune response to a vaccine? It’s possible.
“During natural exposure to SARS-CoV-2, several factors interfere with a robust immune response,” explains Iwasaki. “The exposure dose may be too low. The virus interferes with our immune system (both innate and adaptive) to block the correct induction of antibodies. “
On the flip side, she says, “vaccines are formulated to deliver just the right dose” of viral protein, and there is no live virus to interfere with our immune system. “There seems to be a much more uniform and higher level of antibodies generated with a vaccine,” she says.
At this time, the Centers for Disease Control and Prevention is not making an official recommendation on whether people who have had Covid-19 should be vaccinated; he awaits input from the Advisory Committee on Immunization Practices, a group of medical and public health advisers who make recommendations on how to vaccinate the public. Although we know from clinical trial data and the Food and Drug Administration’s review of it, Pfizer / BioNTech and Moderna vaccines appear to be very safe for the general public.
But have they been proven to be safe, in particular, for people who have already been infected? There may not yet be enough data to say this definitively. “I think the answer is probably yes, but we won’t know for sure until the numbers get bigger,” writes Helen Y. Chu, University of Washington immunologist and physician in an email. “For most of the Phase 3 trials, there was no screening for pre-existing antibodies.”
Keep in mind that the lack of safety data for this particular group does not mean that it is dangerous. As Chu explained, it just needs more data. (Moderna vaccine specialist Jacqueline Miller on Thursday told an FDA advisory panel that the company “anticipates data in the coming weeks” on how and whether the company’s vaccine strengthens people’s immune systems. who had previously been infected.)
The current data is also not clear: whether the vaccine actually gives to people who have developed a weak immune response to a natural infection – that is, to people who have not produced many cells of the immune system. to fight the virus or whose immune system cells to fight the virus have shrunk over time – an immunological boost.
“It’s not answered yet, but I would say it probably doesn’t hurt,” Chu said. “The antibody decreases over time, and it is likely that the vaccine will increase your titers of pre-existing antibodies.”
That said, based on current test data, both vaccines are around 95% effective in preventing Covid-19. Sette says that a high level of efficacy probably indicates that the vaccine can produce a robust immune response in a large majority of people.
The language of vaccine science is really tricky. Saying that a vaccine protects against disease is not the same as saying that the vaccine makes a person completely immune (or unable to spread the virus). Maybe some people are still infected but clear the infection before symptoms appear. Scientists will need more data on this fine distinction. That said, “it would be difficult to understand that the vaccine gives you 95% protection without inducing an immune response,” says Sette.
Decision making during the pandemic was very difficult. Deciding whether and how to visit friends and relatives leads to a tedious risk-benefit analysis. Fortunately, with vaccines, this decision matrix is much simpler: Even if you’ve had Covid-19 in the past, a vaccine can help prevent future infections. Yes, more data is needed to be absolutely definitive on this. But for now, it’s all pretty encouraging.
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