Thursday, October 28

Why should those infected with SARS-CoV-2 get vaccinated?


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The main objective of the SARS-CoV-2 vaccines generated to date is none other than to protect ourselves from developing the disease and dying. But do we get the same protection by vaccinating that infectándonos Natural way? Is it necessary to vaccinate those who have at some point tested positive for SARS-CoV-2?

Before answering these questions, it is useful to clarify some concepts. The first of them, that the immunization against SARS-CoV-2 can be achieved in two ways: through immunization passive, consisting of the inoculation of antibodies against the virus; or by immunization active, either as a consequence of infection or through vaccination.

While immunization passive is ephemeral, active is complete and lasting. It is due to the fact that it stimulates the proliferation of B lymphocytes, which produce specific antibodies against the virus, and that of T lymphocytes, which induce a specific attack on infected cells.

What does immune memory depend on

The interesting thing about the matter is that a part of these stimulated lymphocytes prevail over time. This means that they act as adaptive immune memory that is reactivated after infection by the same or a similar virus. In the case of being stimulated again, these lymphocytes react faster and more forcefully than the first time they faced the virus, preventing the disease.

Many of the infected people may not have developed a sufficient immune memory to remain protected against the infectious agent.

However, to develop immune memory against the virus, it is not enough to have been infected. It is necessary that the infection has been sufficiently important to induce a robust immune response, capable of stimulating the proliferation and maintenance of various clones of B and T lymphocytes over time.

For this reason, many of the infected people may not have developed a sufficient immune memory to remain protected against the infectious agent after the first exposure.

Natural infection versus vaccination

Natural infection with SARS-CoV-2 induces a more diverse response than current vaccines. This is explained because, while most of the vaccines against SARS-CoV-2 only stimulate immunization against protein S, the infection also exposes us to the rest of the structural and non-structural proteins of the virus.

However, that does not mean that those infected are more protected. The objective of inoculating a vaccine is to stimulation of the immune response whatever the patient’s situation.

Typically, phase II clinical trials study the efficacy and robustness of certain amounts of vaccine inoculum in stimulating the adaptive immune response. It is intended that said stimulation occurs in all vaccinated people and that this answer be robust, something that does not always happen with natural infection.

The good news is that there is evidence that people infected patients who also receive a vaccine dose achieve levels of T lymphocytes and antibodies produced by B lymphocytes similar to those who, having not been infected, receive the two vaccine doses.

B lymphocytes
B lymphocytes

In other words, natural infection would act as the equivalent of a first vaccine immunization. Infected people would require single dose vaccine to achieve the highest level of immunization. The same that a person who has not been previously infected would get after receiving two vaccine doses.

Infected people would require a single vaccine dose to achieve the maximum level of immunization

But how do you determine who has been infected and who has not? It is not easy. Perhaps the most reasonable thing would be to consider infected only those cases that accompany the symptoms of covid-19 with a confirmed diagnosis.

It seems clear that the levels of immunization achieved after infection, or after a single vaccine inoculation (pending what happens with the single dose vaccine of the company Jansen), may be insufficient to prevent disease.

In addition, in the face of not very robust immune pressure, the virus could adapt and evolve, generating new variants with the ability to evade adaptive immunity.

What is not ruled out is that future vaccine generations will be able to completely prevent infection with a single dose, and even induce a robust and diverse immune response, while being effective, against future evolved versions of the virus.

Estanislao Nistal Villán Virologist and Professor of Microbiology at the Faculty of Pharmacy, CEU San Pablo University. The Conversation ES.

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