Six months and 3,000 million doses after starting the vaccination, experts agree that it would be rare to detect any new side effect: “We have seen it all”
“There has not been a serious side effect in the history of vaccines that has not occurred within six weeks.”
Amós García: “After millions and millions of vaccines, and with a time frame like this, I think everything has already been said”
Have we seen it all?
Adverse effects, “After two months after the vaccine, they have never happened.” Assures it Paul offit, director of the Center for Vaccine Education at Children’s Hospital of Philadelphia. In this informative video from the hospital itself, this pediatrician specializing in vaccines, immunology and infectious diseases explains that all side effects “occur within six weeks after dosing. So the FDA insisted that each of these vaccines be studied for at least two months after the last dose, knowing that there has not been a serious side effect in history that has not occurred in weeks, within the six weeks later to the administration of the dose ”.
The immunologist José Gómez Rial, from the Hospital Clínico de Santiago, seconded it. “Yes, we have seen it all. I don’t think we will discover anything now, in the medium or long term. Now we will see more about the effectiveness of vaccines, whether or not it is lost over time, but nothing new in relation to its side effects. The most serious complications usually appear in the first months ”.
And it is something that studies like this one also point out, which has just been published and confirms the safety of messenger RNA vaccines (Pfizer and Moderna), which are the most inoculated along with that of AstraZeneca. Researchers have analyzed more than one million clinical reports related to these vaccines between December 2020 and April 2021. And they conclude that “serious adverse effects are rare among people receiving BNT162b2 (Pfizer) or mRNA-1273 (Moderna).” They ensure that this study “Reaffirms the safety and tolerability of COVID-19 mRNA vaccines” in the real world.
The first 15 minutes, the first two weeks
Gómez Rial has spent many years researching vaccines, genetics and infections, and he explains the mechanism by which it seems unlikely that these vaccines can give us many surprises that they have not already given us. It begins by warning that “The most important thing is the first 15 minutes. It is the time in which the greatest number of adverse effects appear after administration of the vaccine, such as anaphylactic shock or allergy ”.
This, he explains, “is related to the innate component of our immune system, which is the one that acts in the first place (the innate response). Anaphylactic reactions and allergies appear in a matter of minutes or hours. And the essays are designed to cover that part. “. But what about other more worrisome side effects, like AstraZeneca thrombi for example, that have become known later? That are not detected in the tests, only when a very wide swath of the general population has already been vaccinated. Because they are very rare, very infrequent side effects.
Regarding the Guillain Barre syndrome, Gómez Rial reassures. “It is a syndrome that you can find in almost any vaccine.” Remember that “the vaccine is an immune reaction, although very controlled”, and therefore warns that “In anyone who is already predisposed to an autoimmune disorder, that has conditions, the vaccine acts as a trigger, it can be the last push ”.
In the case of AstraZeneca, thrombi appear between days 3 and 14 after vaccination. In the case of Guillain barre, the 100 cases of this syndrome detected among 13 million vaccinated occurred around two weeks after immunization, although its link to the vaccine has just been confirmed. The myocarditis and pericarditis -all mild- linked to the Pfizer vaccine have been detected shortly after the administration of the second dose of the vaccine.
The “effector cells” and their associated effects
The immunologist explains that adverse effects are related to so-called “effector cells”. And he resorts to an easy-to-understand simile. “The immune cells are like an army, and the effectors are the ones that carry weapons. They are started 15 days after the vaccine and they last a few months. Then there are the antibodies and memory cells, but these are no longer armed, the only thing they are going to do is remember, generate memory of the pathogen to react to it if it reappears ”.
That is, the effector cells are only there in the first few months, “and therefore associated effects may appear, but when they disappear from circulation it would be very rare for something to appear. A few months after vaccination, they disappear ”. The memory cells, which are the most important, “are at rest, they will not generate any problems. Once the cellular memory has been generated, there is no more problem ”.
The passage of time, the best ally
So the passage of time is the best ally. Because There comes a time when, in addition, it will no longer be easy to relate anything that happens with the vaccine. “In the long term, the side effects are tremendously difficult to link to the vaccine, to demonstrate their cause-effect relationship,” explains the immunologist. “With the passage of time, so many things happen in the person, that putting it down to the vaccine is very complicated. The first months are the most important, it is what the history of vaccines has taught us ”.
The vaccinologist Amós García it also confirms it. As time goes by, “the possibility of new side effects appearing is very unlikely,” he says. But it is possible? “It is much more difficult for a biological link with the vaccine to appear now.” Garcia is blunt. “In side effects, after millions and millions of vaccines, and with a time frame like this, I think everything has already been said ”.
The president of the Spanish Vaccination Association also does not believe, therefore, that these vaccines will surprise us with any new adverse effects. And warns. “To me, What worries me the most are the side effects that the disease continues to present, in the medium and long term, which we call persistent covid. In this we can still receive surprises. It worries me is that people do not get vaccinated, not the side effects of vaccines ”.