Without analyzing the data in depth, governments, media and networks have not been slow to advance the need for a third dose of the vaccines. In fact, some pharmaceutical companies have already announced that they will request authorization to do so. But is it really necessary?
The epidemiological data available to date indicate that it is not yet precise that people vaccinated with the complete regimen are protected against the disease, although not so much against contagion. Probably that third dose will end up being incorporated for risk groups with an inefficient immune system, but not for the entire population.
It is necessary to explain very well what is happening and call the population, the media and governments to calm down.
Vaccines protect against disease but not against contagion
Data from countries with high vaccination such as the United Kingdom or Israel show that, while the number of infected people increases almost exponentially, admissions to hospitals and ICUs and mortality are stagnant. Obviously, there is a clear (and very positive) difference compared to the previous waves. And the advance of vaccination is responsible.
To defend the incorporation of a third dose of vaccine, pharmaceutical companies rely on antibodies. One of them has indicated that the third dose of her vaccine greatly increases the levels of antibodies. Of course, yes, as would the fourth or fifth. It increases them because that is what it is about, to induce the immune response in each dose.
But the question is whether more antibodies would be effective in preventing contagion. Would they contribute something new? Well, as indicated a few months ago, no. Also, the studies are only looking at neutralizing antibodies and not another type of immune response.
The antibodies generated by the anti-covid-19 vaccines are antibodies that are released into the blood, of the immunoglobulin G (IgG) type. But the virus infects us through the air, so unless we have IgA-type antibodies in the secretions from our throats, the virus can start the infection.
However, with vaccines we are protected against the disease caused by the virus. And this is so because they induce the production of T helper (Th) and cytotoxic T (Tc) lymphocytes and their corresponding memory cells. These cells are activated as soon as the virus arrives, blocking its proliferation and eventually expelling it. We therefore suffer from an infection. But either we do not suffer the disease that it produces or we suffer it in a mild way.
Margarita del Val, virologist and immunologist at the CSIC, said a few days ago at a seminar at the Institute of Biomedicine of Seville (IBIS) that we are all going to get infected sooner or later, but the important thing is that you get infected after having been vaccinated. So you can face the infection but protected. Nothing more to add.
Precisely for this reason, in the United States the highest mortality is occurring in the unvaccinated population. They are not protected against disease.
The variants do not seriously affect the immune system.
One of the reasons being put forward to push us to a third dose is that the variants escape the immune system. But scientific studies indicate that this evasion is partial and does not affect all the places recognizable by antibodies or T lymphocytes.
It must be emphasized that the immune response is polyclonal. This means that antibodies and T lymphocytes do not recognize a single place but each one recognizes a different one. The joint response occurs on many antigens of the virus or protein S.
This way of responding implies that if the virus undergoes a mutation in a certain position, there are many others that remain unchanged and that the immune system recognizes.
A purely evolutionary question also enters this game. The virus uses the ACE2 protein as a lock to open the cell door and its S protein as a key. We could consider that the most infectious variants are tuning the key to better and more efficiently enter the lock. Thus they increase its effectiveness to infect.
Antibodies and lymphocytes are also fine-tuned to detect those particular key teeth. Therefore, to escape the immune system, mutations must modify the key. This will lead to a situation in which any modification of the S protein to escape the immune system will cause it to lose its effectiveness to spread.
The virus co-evolves with humans. It is very possible that it will end up being the fifth type of coronavirus that affects humans that causes seasonal colds and little else.
Wait for herd immunity and data
Science takes time to reach conclusions. Making decisions hot and scared leads to rash and generally wrong decisions. Governments, without having yet vaccinated the entire population and without having verified whether this is sufficient, should not fall into the error of going for a third dose of vaccine.
There is a large population that has not yet received their doses. Before considering a third dose, we must vaccinate the entire population or, at least, most of it.
The data suggests that the disease will behave like any respiratory infection if you are vaccinated. COVID-19 will thus cease to be serious even if there are infections.
Guillermo López Lluch, Professor of the Cell Biology area. Associate researcher at the Andalusian Center for Developmental Biology. Researcher in metabolism, aging and immune and antioxidant systems, Pablo de Olavide University
This article was originally published on The Conversation. Read the original.
