The restriction of vaccinating with AstraZeneca people under 60 in Spain has caused many people to have only been immunized with one dose of this drug. For this reason, the Carlos III Health Institute (ISCIII) has promoted a clinical trial which will evaluate the possibility of administering a second dose of Pfizer in these cases.
The study, called CombivacS, will analyze in 600 patients the possible protective effect and safety of giving a dose of this vaccine from Messenger RNA in order to covid-19 to people who have already received a first from the British laboratory after a minimum of 8 weeks have elapsed since the first injection.
CombivacS will analyze in 600 patients the possible protective effect and safety of giving a dose of Pfizer to people who have already received a first AstraZeneca after 8 weeks from the first injection.
During the presentation of the essay, the director of the ISCIII, Rachel Yotti, has indicated that it is about “generating scientific evidence” to verify the safety of combining other vaccines with the British drug and “support decision-making in relation to possible alternatives to those already immunized with a dose of AstraZeneca.”
During the clinical development of the vaccines Comirnaty (Pfizer) and Vaxzevria (AstraZeneca), different studies have been developed to define the dose, efficacy, safety and conditions of use of each one of them individually. Although both have been available in Europe for some time, until now there are no clinical data on their possible combined use.
The joint use seems possible and even desirable, since they are vaccines that act with different mechanisms of action and there is evidence that this way of dealing with other diseases can be beneficial, but clinical trials like this one need to be carried out to verify this.
In fact, CombivacS is one of the first clinical trials to examine the safety and immunogenicity of this type of combination regimen. The study will unfold in five hospitals: La Paz and Clínico San Carlos in Madrid; Vall d’Hebron and Clinic, in Barcelona, and Cruces in Vizcaya. The National Center for Microbiology (CNM) will act as the central laboratory for the trial, which has had the advice of the Spanish Agency for Medicines and Health Products (AEMPS).
Quantify the number of antibodies
This is a phase 2, comparative, randomized and adaptive clinical trial to evaluate the safety and immunogenicity (ability of the immune system to respond successfully to an infection) of a dose of the vaccine called Comirnaty (Pfizer) in people who have previously received a dose of Vaxcevria vaccine (AstraZeneca).
The study analyzes the possible combination of more than one vaccine (heterologous vaccination regimen) with different mechanisms of action to complete the desired immunization. The starting hypothesis is that said immunogenicity will be greater in the group that receives two different doses of vaccines compared to the single dose.
The primary objective of the trial is to verify whether in people who have already received a dose of AstraZeneca vaccine there is a significant increase in their levels of antibodies against SARS-CoV-2 after 14 days after receiving a dose of Pfizer
The primary objective of the trial is, therefore, to check whether in people who have already received a dose of the AstraZeneca vaccine there is a significant increase in their levels of antibodies against SARS-CoV-2 after 14 days after receiving a dose. from Pfizer.
For logistical reasons, only people residing in the provinces where the five participating hospitals are located will be eligible. The first results are expected 5 weeks after the start of the trial. If these results were favorable in terms of safety and efficacy to the sequential vaccination scheme, a dose of Pfizer will be offered to all participants in the control group.
Volunteers divided into two groups will participate in the trial, to which they will be randomly assigned. On the one hand, group 1 or intervention group, made up of 400 people, will receive a dose of the Comirnaty vaccine (Pfizer), followed by 28 days of clinical observation and antibody analysis for a year.
For its part, group 2, which will be made up of 200 people, will not initially receive any vaccine. This group 2 will act as a control group, all surveillance, security and analysis procedures being identical to those of the experimental group. The comparison of the immune response between the two groups will be carried out on some analyzes obtained 14 days after the inclusion of each volunteer, without prejudice to other very exhaustive analyzes that will be carried out over a year.
Results from this study are not expected earlier than 4 weeks after the first person receives a dose of Pfizer.
Taking into account that the participants will need a minimum of 7 days to join the study and that thousands of samples must be analyzed, it is not expected to obtain results before 4 weeks after the first person receives a dose of Comirnaty (Pfizer). In any case, if the results so advise, 28 days after the start of the study, the Pfizer vaccine will be offered to all patients who had not initially received it (group 2).
Finally, the researchers also seek to obtain knowledge about the immune response conferred by the sequential combination of both vaccines over a year, as well as protection against SARS-CoV-2 variants at 14 and 28 days after complete vaccination.
Carlos III Health Institute
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