Sunday, June 20

Combining two different covid vaccines multiplies adverse reactions | Science


Vials of various vaccines.  Their combination is being tested in several countries to speed up vaccination.
Vials of various vaccines. Their combination is being tested in several countries to speed up vaccination.DADO RUVIC / Reuters

The first results of a study in which different vaccines are alternating between the first dose and the second shows that adverse reactions are multiplying. The research reveals that the cases of fever, muscle or joint pain and generalized fatigue tripled among those who received a combination of the inoculated Pfizer (Pf) and AstraZeneca (AZ) compared to those who were only punctured with one of them. twice. The work, still in progress, indicates however that these side effects are not serious, are short-lived and are alleviated with paracetamol.

Before a few dozen cases of thrombi prompted many European governments to rethink their vaccination strategy with the AstraZeneca formulation, a study combining the vaccines had been launched in the UK. The essay, called Com-TheIts main objective is to check whether administering different inoculates in the first and second doses affected (improving or harming) the generation of antibodies (immunogenicity). Then, last February, the trial coordinator, Oxford University researcher Matthew Snape explained his motivation: “If we can show that these combination plans generate an immune response that is as good as normal strategies and without an increase significant of reactions to the vaccine [reactogenicidad]This could allow more people to complete their covid immunization in less time. “

The results of the work on efficacy or safety will not be ready until June. The delay has its explanation in the design of the trial. Of the 830 volunteers recruited, almost half will have the second dose punctured 84 days after the first. That is, they will be putting it on these days. However, the magazine The Lancet has just published preliminary results on the reactogenicity caused by vaccines among the other half, which received the two doses in a span of 28 days.

The first thing they notice is that the climax of the reactions is different for each of the vaccines. Thus, with the AstraZeneca most problems occur after the first puncture. Meanwhile, with Pfizer, it is after the second. But the most striking thing is that, compared to those who received the same vaccine in both doses (Pf + Pf or AZ + AZ), among those who received a combination, most of the most common side effects multiply.

The most common of all, for example, is the appearance of fever. Well, among the 110 study participants who first received the AstraZeneca shot and then the Pfizer shot, 34% had febrile episodes, though none were really serious. That is tripling the 11 cases out of 112 (10%) of those who had a fever after receiving the two doses of AstraZeneca. Meanwhile, in those who first received Pfizer followed by AstraZeneca, volunteers with a few tenths more were 41% of the total, compared to 21% of those who received Pfizer both times. There was no case that reached 39º.

Only 10% of those inoculated with the AstraZeneca vaccine in both doses had a fever compared to 34% of those who received this formulation and then that of Pfizer

These differences are maintained in the rest of the more common adverse reactions. The cases of headache, muscle or joint pain generally double among those who received different vaccines in the first and second doses. Something similar happens with chills, general malaise or fatigue, although here the total number of cases is lower. Where there is no variation is in the local pain in the area of ​​the puncture, no matter what vaccine it is, the area of ​​the puncture hurts for hours. Nor does the incidence of nausea or diarrhea vary. Most of the cases were mild and moderate and none required hospitalization. Furthermore, the vast majority of them disappeared in two or three days. Although acetaminophen intake is not included in the trial, the researchers did recommend it by the researchers, and the volunteers reported that it served them well.

Snape, the trial coordinator, says in a note that, without being serious, “the results of this trial suggest that plans to mix doses could lead to increased absences from work the day after immunization.” It also highlights that they have not found serious safety problems, such as thrombi or serious allergies, but remember that this trial is carried out with people over 50 years of age and there is the possibility that those under that age have more and more intense adverse reactions.

The combination of vaccines is also being tested in Spain. Called CombivacS, the study will look at the protection and safety of giving a dose of the Pfizer vaccine to people who have already received a first dose of AstraZeneca. The aim is to remove from limbo those who have already been vaccinated with the latter in the first part of the guideline. The first results will be published next week, they say from the Carlos III Health Institute, which coordinates the trial in which 600 people participate. Like the British, CombivacS will also monitor possible adverse reactions when mixing vaccines.

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