1. Antibodies beyond 7 months in the majority of recovered
If you have doubts about whether or not you have received a vaccine or if you have had an infectious disease, you can do an immunity serology. In this blood test it will be seen if there are antibodies or not, generated by the organism when it has come into contact with a virus.
The normal thing is that you are protected, precisely thanks to them, since their function is to try to block the access of pathogens to cells (neutralizing antibodies) and to sound the alarm so that the cellular army of our defenses is activated.
Most studies to date reach two conclusions. Antibodies after passing the COVID are durable. How much? Minimum, what we have of a pandemic. Two recent samplings come to the preliminary conclusion that at least between seven (6,000 people studied at the University of Arizona) and eight months (185 convalescent, in California) And they have been able to measure that the rate of fall over time of the antibody titers is slow.
It is possible that those who have had mild or asymptomatic SARS-CoV-2 coronavirus see how many of their “Long-lasting” antibodies (IgG) disappear after the second or third month. It is believed to have to do with viral load that that organism endured. If it was short, hopefully he had hardly any symptoms, but the duration of the antibodies does not seem long in some people in this group either.
And beware, not all antibodies are the same. Some may decline, but the truly important seem to be the neutralizers that go for the protein S of the virus. That is, the tips or keys with which it makes its way into the locks of the cells. That is exactly the target of the main vaccine candidates.
2. T, B, NK. Not everything is antibodies in the immune alphabet soup
Even without antibodies, the body continues to defend itself. A healthy, well-trained immune system has memory cells. When the virus returns (or has seen parts of it in vaccine form), it quickly pulls through the list of the most wanted pathogens. And it goes for him. That’s where the T and B cells (or lymphocytes).
‘There is strong data to suggest that T cell response is also important for protection and immunity against SARS-CoV-2 and is possibly independent of the antibody response “, Sydney Ramirez explains to Newtral.es from the La Jolla Institute of California. In July he co-published a study in Cell that now complements this preliminary work on antibodies, and another by a team from Wuhan, China.
There they saw that about thirty patients they retain immunity today thanks to their T cells, that seen under a microscope, they launched themselves to attack SARS-CoV-2 when they were exposed in a laboratory dish, which suggests that the same thing will happen in their body, if the virus returns. It is true that Wuhan, precisely, is free of coronavirus, so checking this, for now (and fortunately) is difficult.
Major trials of more advanced vaccine candidates have measured T-cell response. And it seems that everything is working as expected. After receiving the vaccine dose (s), they appear to be trained.
They have also observed in La Jolla that there are other memory-conserving cells after passing the infection and, surely, after being vaccinated. NK (Natural Killer) lymphocytes They are true destroyers, heavy artillery of the defenses that also remember the bad guys. And next to this gross line, the B lymphocytes. This is very important, because they are responsible for making antibodies.
3. Missing Antibodies May Come Back
The La Jolla Institute team has observed that the number of B cells in convalescents continues to grow over time. That may explain why the antibody levels in some people, in different tests over time, are so different. First low, then skyrocket, then decline and rise again.
The study is interesting because it focused on mild covid patients. And he is the first to look at the immune response to a virus in such detail.
4. Antibodies derived from other diseases or vaccines can help
The subject of the call cross immunity it remains as interesting as it is controversial. It is not easy to measure the extent to which having passed other infectious diseases helps the defenses to combat SARS-CoV-2. As we have explained here, in general, everything helps. But a past cold does not guarantee protection against covid.
It is possible that exposed to other cold coronaviruses leave our defenses on alert. And in case of contracting SARS-CoV-2, everything remains in a mild or asymptomatic covid. As if it were a moderately effective vaccine. Would that explain the lightness of the covid in children?
La Miseria, by Cristóbal Rojas. A picture of tuberculosis, whose immunity is now important.
For this, there must be a condition: that the natural defenses are ready. And as the immunologist Margarita del Val (CBMSO-CSIC) explained here, the older we get, the worse our defenses tend to organize.
Along the same lines, other vaccines can help the body fight SARS-CoV-2. For example, one line of research holds that prophylaxis such as tuberculosis helps contain infection (not prevent it). In the same way as the flu vaccine.
Yes, we can not trust
As in almost everything related to this new coronavirus, there are still unknowns to be solved. And immunity is a complex puzzle. Starting because the answer of each person can be very different. This may explain the few, but not negligible cases of reinfections proven.
In immunity, each person can be very different and respond in different ways, especially when they are older.
Continuing because the most serious covid is a disease, most of the time, derived from an imbalanced response of that immune system.
A proof of this is that if point 4 applied to 100% of the population, last spring of 2020 would not have been an unprecedented drama in the recent history of mankind. It is evident that there is a population group (especially the elderly and with previous pathologies) that was not at all protected from severe covid, due to many past colds or vaccines that they had put on.
Is the high proportion of asymptomatic or mild because of that more or less trained immunity from other coronaviruses or pathogens? Can be. But it’s not enough. Hence the need for effective vaccines in all population groups. Adding up all the pieces of the immune puzzle, it seems that, at a minimum, the first candidates will give us lasting protection against the most serious covid.
It remains to be seen that they prevent the virus from reproducing enough in our cells for us to be contagious. And thus stop the visible or invisible transmission chains.