Sunday, June 20

Coronavirus: The epidemic reaches its lowest levels in Mexico


A teacher receives a dose of the CanSino vaccine in Guadalajara on April 28.
A teacher receives a dose of the CanSino vaccine in Guadalajara on April 28.ULISES RUIZ / AFP

Mexico has been one of the countries that has suffered the most from the pandemic. Hundreds of thousands of deaths divided into two great peaks that, today, are in their steepest valley since practically the beginning of the problem.

Since the beginning of the slow but inexorable rise of the first wave, Mexico did not register such a low level of daily deaths. Even taking into account the exception of the natural delays between the moment of death and the epidemiological curve, these low volumes are remarkable. There are several factors that can help explain them, especially in contrast to the upward trend that the pandemic presents throughout the world. They all go through a concept that both Mexico and the entire world have become accustomed to: immunity.

The body is capable of developing certain defenses to counteract both contagious diseases and the viruses that cause them. These defenses can be acquired by past infection, thanks to which the body learns how to repel the following ones. It can also be earned through vaccination.

Since the end of December, Mexico has administered around 15 doses per 100 inhabitants. Less than half (barely 6%) have the complete vaccination schedule, which in the case of all vaccines used in the country is double-dose. It is difficult that this incidence has been a significant brake on contagion or the disease that derives from it. In the data, it is hardly guessed that those over 60 do have a slightly greater decline in deaths during April, but it seems difficult to draw strong conclusions.

The other route to immunity is much less secure, but perhaps a certain ceiling has been reached in some parts of the country. Both the generation of antibodies and the development of tools in certain cells (B, T) is common and observable after an infection with SARS-CoV-2. His strength, yes, is not constant neither in time nor between people. In some bodies it can develop better than in others, and ends up losing defense capacity as the months go by.

Even so, the strong impact of the virus on capitals, particularly in Mexico City, could have equipped a majority of the population with these tools.

It has done it at an enormous cost in human lives, yes. And it’s not even insurance forever. The first reason is mutation: the pathogen is capable of adapting its attack forms to partially or totally evade immunity. Following an evolutionary logic, the inertia of contagion produces thousands of mutations that serve as “hook tests” in the human body. Some, because they are more effective at this or due to other genetic or population factors, manage to survive by dodging to a certain extent the defenses developed in the past.

The Institute for Epidemiological Diagnosis and Reference (Indre) announced this week that it has detected the presence of variables of British (B.1.1.7) and Brazilian (P1) origin in the country. But, unlike what has happened in Colombia or Chile (both sharing a border and intense connections with Brazil), such detection has just taken place, when it is already probable that places like Mexico City are in the 60% or range. 70% cumulative incidence. This lack of early importation of the variants, together with the very high waves of the past, would be saving Mexico from the third peaks that have been seen in countries like Colombia.

However, it should be clarified that these estimated percentages do not translate, far from it, into permanent group immunity. It is not only that defenses vary between people and over time, as well as in their ability to confront new mutations. It also happens that these socks provide an oversimplified image of the spaces that the virus has to survive. What is expected is that the majority of people who have already been infected belong to sectors related to each other, than with more intense relationships between one and the other. The other side of the coin is that if the virus manages to enter those that remain, it could, if not grow significantly, at least wait for better times (a mutation, a decrease in defenses due to the passage of time). For this reason, and until true immunization through vaccines does not reach a large majority, Mexico cannot claim victory.

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