Selling antigen test in the Spanish pharmacies It has come at a time when a large part of the adult population is fully vaccinated. Even some teens and children over 12 years old already have at least one dose. But there are still quite a few people who have not received the complete guideline from any of the coronavirus vaccines. And, as a consequence, some doubts may arise.
For example, if the vaccine introduces us in one way or another viral antigensWouldn’t the test be positive if we did it immediately?
This is a question that has crossed the minds of many people when taking one of these tests. However, there are two simple reasons why the vaccine does not invalidate test results: the way the samples are taken and the protein used.
Before we begin, it is worth remembering how the two inventions we are talking about work. On the one hand, coronavirus vaccines they carry a viral protein in one way or another to our cells, so that the immune system build defenses against it. Thus, in the event of a real infection, you are already prepared to fight it.
At present, in Spain the two vaccines that are being administered the most are those of Pfizer and Moderna, both of Messenger RNA. These contain the molecule that carries the instructions for the cellular protein factories, calls ribosomes, make the virus protein S. That of AstraZeneca, which was administered at the beginning of the vaccination to essential personnel and people between 60 and 70 years old, does not introduce the messenger RNA, but the gene that codes for a viral protein. Therefore, it will be the cellular machinery of the vaccinated person that will have to obtain the messenger RNA and, from there, again the protein. Very similar is the operation of the single-dose vaccine of Janssen.
Now, what do antigen tests do that we can acquire in pharmacies? Basically, they detect the presence of certain coronavirus proteins in our cells. That could lead us to think that, indeed, if we have vaccinated the self test, or even a laboratory test, could give wrong results. However, there is a reason why we can use both tools without any problem.
Nasal sample and protein type
Antigen tests, like PCR, detect the presence of the coronavirus in its gateway to the body.
It is known that it can be introduced through the mucous membranes, especially nose and throat. For that reason, samples for any of these tests are collected from these areas. The most common thing, if the test is going to be carried out by a laboratory or a health professional, is that a nasopharyngeal swab. This is the famous procedure by which a stick, called a swab, is inserted through the nose and led to the throat, where they take a few turns to collect the cells on which the test will be performed.
Getting there is not easy. You need to do it qualified staff. For this reason, the pharmacy self-tests are prepared so that we can collect the sample ourselves, introducing the swab only in the nose, without reaching the bottom.
Be that as it may, we keep talking about the entry of the virus. However, in the case of coronavirus vaccines, the viral protein does not enter through the mucosa, but rather injected intramuscularly. Thus, a systemic action is achieved throughout the body. But not in the mucous membranes.
In fact, this is also one of the reasons why vaccinated people can continue to be infected and contagious, since the immune response will not be generated just in the mucous membranes through which the virus makes an appearance. Things will change when we have nasal vaccines, like the one being prepared by the Luis Enjuanes, Isabel Sola and Sonia Zúñiga, in Spain. But, for now, it is what we have.
And that’s not all. There is one more thing why both tools do not interfere. And, while vaccines introduce the coronavirus protein S into our body, antigen tests generally detect another, protein N.
Therefore, there is no problem. If we need to do a conventional antigen test or a pharmacy self-test there will be no problem for having vaccinated before. If it is positive, it will be because there is infection. Coronavirus vaccines do not influence the result, nor do they influence the PCR.