What we seem to ignore about COVID-19 immunity
Are we really immune once we survive COVID-19?
Earlier this year, a Chinese study published in the Journal of Clinical Microbiology and Infection caused panic among the public due to the conclusions made by the authors:
“We herein estimated the longevity of specific antibodies against SARS-CoV-2 in a moderate COVID-19 patient, and reported that antibodies disappeared within 3 months after the onset of the symptoms.”
These claims alarmed the general population, as many understood that the lack of antibodies would be a synonym for lack of immunity. Therefor, people that were previously infected with the virus SARS-CoV-2 would be at risk of reinfection once again after a few months.
However, to me, this misunderstanding seems to have been caused by incomplete and sometimes incorrect information given by the mainstream media.
In 2003, a mysterious respiratory illness appeared in China, today we refer to it as SARS, which stands for severe acute respiratory syndrome. Relatively speaking, at the level of the individual, this was a more serious disease than the current one (COVID-19). Luckily for us, due to multiple reasons, this virus was rapidly controlled and was not capable of expanding to more than a few thousand cases around the world.
In a sense, SARS shares many characteristics with COVID-19. But two that I find peculiarly interesting are (1) there are some people that develop a kind of post-illness syndrome (2) antibodies don’t seem to last forever.
(1) A case study published in 2011 followed mostly healthcare workers who couldn’t get back to work after recovering from the acute infection. These individuals suffered fatigue, myalgia, weakness, poor sleep and depression. I was able to contact one of the authors, and I unfortunately I was told that the patients did not respond to “physiotherapy, occupational therapy, and psychotherapy”. Unfortunately, they couldn’t continue the study due to lack of funding. However, long-COVID is not the point of this article, but rather immunity.
(2) We are aware that antibodies did not last long in SARS patients. Indeed, on average, the antibodies lasted an average of 2 years according to a study in 2007, “thus, SARS patients might be susceptible to reinfection”, says the article.
However, luckily for us, antibodies are not the only mechanism of long-term defence our body develops against viruses. For example, even if your antibody count goes to zero, you may still have the B cells. These are the producers of antibodies, which can be laying around waiting to be reactivated by a potential reinfection.
In addition, we have T-cells. These are cells capable of also developing specificity towards coronavirus, specifically, they destroy infected cells. However, what do we know about T-cells in coronavirus?
Well, as I mentioned before, antibodies seem to decay rather fast after infection of both SARS-CoV and SARS-CoV-2. However, we also know that even after 11 years, these specific T-cells are still present and functional in recovered individuals from SARS-CoV, according to this study.
However, what about when you are ill after COVID-19? Well, a study published in Cell, lead by a Swedish team found that these T-cells are even present on asymptomatic individuals. Even more, in June, when they measured antibodies in the population of Sweden, only around 7% of the population had antibodies. However, when the T-cells were measured, 30% of the population had them (see story here). Furthermore, newer studies show that these T-cells are present over 6 months after infection.
To summarize, immunity so far seems to be efficient, and based on our previous experience with SARS, it may be also long lasting. We seem to be in a good path at achieving major social immunity. Finally, as scientist have said, and as what research has shown us, reinfection seems possible, but a “rare phenomenon”.
Disclaimer: While I am a trained scientist who focuses on biomedicine and neuroscience, I am not an expert on immunology nor virology. I am neither a medical doctor. Everything written here should be taken with discretion. At the same time, the information provided in this article is accurate to the date of publication. Things in science change very quickly, so if this article is old, things may have changed, leaving the article outdated.
