The Ministry of Health will initiate the application of a serological survey to detect antibodies and identify people who are immune to COVID-19, the Undersecretary for Prevention and Health Promotion, Hugo López-Gatell, reported.
The federal official noted that the most optimal time to apply this survey is when it initiates the decline of the epidemic curve, that is, at a time when the number of accumulated cases is greater but the number of new daily contagions drops.
«For COVID we are also already planning to do serological surveys, surveys that allow us to know the proportion of people in Mexico who have immunity to COVID,» he announced during the daily conference to report on the evolution of the pandemic.
Read: Mexico exceeds 5 thousand deaths per COVID-19; there are 10,681 active cases
He detailed that the survey will consist of both a serological test and an interview that allows the collection of sociodemographic data from people.
«Serological survey means an interview to do the recognition of certain demographic, social, and also the course of the disease, there are going to be questions about: ‘Have you in the last 30 days had a fever, cough, etc.?’, among other questions, but after (also) the taking of a blood specimen, that blood specimen is removed the serum, the serum is the liquid component of the blood, the blood has fluid, proteins and cells – white blood cells, red blood cells and platelets – but the liquid part, which is the serum, is done that studies are done to identify the antibodies.
«And there are two kinds of relevant antibodies, there are five classes, but those that are relevant to this are the IgM-type antibodies, which are acute phase, begin to increase their concentrations in the first few days after infection and usually last a short time, four, five, six months, and there are the IgGs, which remain, take longer to start and remain,» the official explained.
Lopez-Gatell said the serological survey will be applied in workplaces, as Advanced Political Animal, and will also be incorporated as part of the National Health and Nutrition Survey (ENSANUT).
«These are several survey exercises that we will be doing, some have to do precisely with the technical guidelines for Health Safety at Work that we have been talking about recently, to conduct surveys in the areas of work, in companies, particularly medium and large, and also the National Health and Nutrition Survey, which from 2020 on which is an annual survey, is a survey conducted by the National Institute of Public Health, we are already planning to include a COVID component and also a COVID seroencuesta,» he said.
«In Mexico, at least as a government effort, we have not initiated any (survey of this kind), among other reasons, because it is more convenient to wait for the moment when the epidemic curve decline is, because otherwise the information of now ceases to be relevant afterwards, unless, in the beginning, very high proportions of people are already immune.»
The undersecretary acknowledged that there are limitations of the serological survey, which have been suffered by countries that have already started its implementation, such as the United States (promptly New York), France and Spain.
«One of the limitations facing the whole world is that, although more than four months have passed since the onset of this epidemic, there is no solid, consistent scientific evidence of consensus, about when antibodies about the day of infection begin to increase, how much the concentration rises, how long they last and, most importantly, whether the concentration that can be observed means biological protection; at some point, I’m sure, this information will find consensus and be extraordinarily useful,» he said.
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