Do people who have passed COVID-19 have more immunity than vaccinated people?
When we fall ill with COVID-19, our immune system recognises all the molecules of the virus as foreign and sets in motion many effector mechanisms that include the production of antibodies and T cells to target the proteins of the detected virus. However, during vaccination we are only confronted with the S protein of the virus, so we generate high levels of antibodies and T-cells against this particular protein. This response to the S protein is what protects us against the disease, because this is the protein that the virus uses to infect our cells.
Therefore, vaccination confers greater protection against the main route of entry of the virus, with high levels of antibodies being generated against protein S, while post-disease immunity induces moderate levels of antibodies against different proteins of the virus.
Thus, we can say that vaccine-acquired immunity is generally more potent than that obtained once COVID-19 has been passed, and also offers greater protection in the medium and long term.
In other words, if the disease is defeated, immunity is more comprehensive, but less potent and it also depends on the severity of each case. It is therefore recommended that at least one dose of the vaccine be administered to people who have had the disease, as a booster to generate a more robust immune response.
Mucous membrane protection
The only immunity advantage we can point to from having had the disease is the production of IgA antibodies, which are mucosal protective. These IgA are most useful in the early stages of the disease, when the virus is multiplying in the respiratory tract. Current vaccines, which are administered intramuscularly, basically generate IgG antibodies. IgG antibodies are very potent in neutralising the infection and can perform even more protective functions than IgA antibodies, but they are mainly located in the blood plasma.
As for the duration of antibody protection, there is still no certainty because vaccines are very new. Therefore, it is still too early to know whether a third dose of some of the current vaccines will be needed.
Answered by María Luísa Gil Herrero, full professor at the Department of Microbiology and Ecology of the University of Valencia.
Question submitted by Jonathan Valladares.
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