Think you are protected against the Covid-19 coronavirus and don’t need the Covid-19 vaccine just because you’ve already had Covid-19? Well, contrary to what some motivational talks may tell you, don’t be so sure of yourself. A study just published in the journal Emerging Infectious Disease found that 36% of those who had had Covid-19 didn’t have antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in their blood.
That’s over a third, or more than the percentage of Americans who consider a hot dog to be a sandwich. In other words, it is a sizeable percentage and serves as further evidence that you should get the Covid-19 vaccine even if you’ve already had a Covid-19 coronvirus infection.
For the study, a research team, led by first author Weimin Liu, M.D. and senior author Beatrice Hahn, M.D. from the University of Pennsylvania, checked blood samples from 72 people who had tested positive for the Covid-19 coronavirus via RT-PCR tests. All but two of the people had had symptoms, with 13 (18%) having mild disease, 48 (67%) moderate disease, and nine (12%) severe disease. They waited at least three weeks after each person no longer had symptoms before checking their blood.
Only 46 of the 72 participants ended up having detectable antibodies against the Covid-19 coronavirus spike protein in their blood samples. Plus, the amount of antibodies detected ranged significantly from 182 to greater than 312,500. They found similar results for antibodies against other parts of the virus including the receptor-binding domain (RBD) and nucleocapsid (N). Ultimately, 26 (36%) remained seronegative, meaning that they never developed detectable levels of such antibodies in their blood, even when multiple blood samples were checked for each person.
The research team found that those who didn’t develop antibodies were on average 10 years younger than those who did. The study also revealed that people who had lower SARS-CoV-2 viral loads in their respiratory tract were less like to subsequently have antibodies in their blood.
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Now a study of 72 people probably wouldn’t qualify as a gigantic study, depending on what you may consider and refer to as gigantic. Nevertheless, it certainly hasn’t been the first study to show that people who have had Covid-19 may not end up developing antibodies. For example, as described by a publication in EClinical Medicine 5% of 698 people in Israel remained seronegative despite having tested positive for the Covid-19 coronavirus. Another study, published in the Journal of Infectious Diseases, found this rate to be even higher (20%) among a group of New Yorkers. Then there was the study from Germany published in the Journal of Clinical Virology which reported a whopping 85%.
Of course, antibodies are not the only measure of immune protection against SARS-CoV-2. Checking for antibodies can be like checking whether your friend is carrying a scimitar. Having a scimitar may offer some comfort that you are protected and prompt you to say, “oh, great, you brought your scimitar. We shouldn’t have any problems when ordering at the restaurant.” However, the lack of antibodies or a scimitar doesn’t necessarily mean that you have no protection whatsoever. Even without detectable antibodies, your immune system may still have other defenses at work. However, if someone were to ask you, “would you like to have antibodies against SARS-CoV-2,” your answer probably wouldn’t be, “no, I’d rather have the steak.” Lack of antibodies suggests that you may be more vulnerable.
All of this isn’t that surprising since having Covid-19 is not like watching the 2016 movie Dirty Grandpa. While being infected with the Covid-19 coronavirus certainly is not a pleasant experience, it’s not equally bad for everyone. The severity of symptoms and problems can range greatly from no symptoms to severe problems to death. Moreover, the duration of symptoms can vary substantially too. Therefore, one could expect the resulting immune protection to vary significantly as well.
at’s why relaying solely on supposed immune protection from a previous Covid-19 coronavirus infection could be like relying solely on a thong when going on a date or a job interview. The bottom line is that both can still leave you quite exposed, and the amount of exposure can vary quite a lot from person to person. That’s why the Centers for Disease Control and Prevention (CDC) and other public health experts continue to recommend that you get the Covid-19 vaccine regardless of whether you’ve already had Covid-19. As I have covered for Forbes previously, another reason to get vaccinated is that natural immunity differs from a smartphone. You don’t know how long it may last. In the case of the smartphone, the answer may be “one day after the warranty expires,” whereas the duration of protection offered by natural immunity may be all over the place.
By contrast, the Covid-19 vaccines offer a much more controlled and consistent amount of exposure to the SARS-CoV-2 spike protein. While person-to-person immune responses to the vaccine may vary as well, clinical trials are following thousands of people who have gotten the vaccines. Therefore, researchers can get a better idea of what kind of immune protection the vaccines may offer you. If you want to hold a rabbit rave, it may be much more effective to go to a pet store than to go to the woods with sign that says, “have carrots, let’s party.” Similarly, if you want immune protection against Covid-19, vaccination may be much more likely to give you what natural infection may or may not be able to offer.