Clinical trial designed to evaluate the safety and immunogenicity of a dose of Comirnaty vaccine (Pfizer) in people who have previously received a dose of Vaxcevria vaccine (AstraZeneca)

Description of the Study:

  • Title: CombivacS.
  • Principal Investigators:  Joan Albert Arnaiz, José Ramón Arribas, Magdalena Campins, Antonio Pórtoles Pérez, Luis Castaño González, María Teresa Pérez Olmedo and José Alcamí.
  • Centers of Implementation: It will be promoted, coordinated and financed by the ISCIII, and will be carried out in five hospitals: La Paz and Clínico San Carlos in Madrid; Vall d’Hebron, Hospital Clínic in Barcelona, and Cruces in Vizcaya.
  • Study Population: 600 people randomly selected from among those who have received a dose of Vaxzevria vaccine (AstraZeneca), provided that a minimum of 8 weeks have elapsed between that dose and the start of the trial and that they are less than 60 years of age. Only persons residing in the provinces where the five participating hospitals are located will be eligible.
  • Study Type: Phase 2, comparative, randomized, adaptive and comparative clinical trial.
  • Design: To evaluate the possible increase in antibodies, the number of antibodies in a group of people who have been previously vaccinated with a single dose of Vaxzevria (AstraZeneca) but who will not initially receive the dose of Comirnaty (Pfizer) will be analyzed simultaneously.
  • Methods: The trial will involve volunteers divided into two groups, to which they will be randomly assigned.
    – Group 1 or intervention group, consisting of 400 people, will receive one dose of Comirnaty vaccine (Pfizer), followed by 28 days of clinical observation and antibody testing for one year.
    – Group 2 or control group, which will consist of 200 persons, will not initially receive any vaccine. This group 2 will act as the control group, with all monitoring, safety and analytical procedures being identical to those of the experimental group.
    The comparison of the immune response between the two groups will be made on the basis of analyses obtained 14 days after the inclusion of each volunteer, without prejudice to other very exhaustive analyses to be carried out over a year.

Objectives of the Study:

Principal Objective: To check if in people who have already received a dose of Vaxzevria vaccine (AstraZeneca) there is a significant increase after 14 days in their SARS-CoV-2 antibody levels after receiving a dose of Comirnaty (Pfizer).

Secondary Objectives: To gain knowledge on the immune response conferred by the sequential combination of both vaccines over one year, as well as protection against SARS-CoV-2 variants at 14 and 28 days after completion of vaccination, among other issues.

More about this Study:

El Centro Nacional de Microbiología (CNM) del ISCIII will act as the central laboratory for the trial, which has received scientific advice from the Agencia Española de Medicamentos y Productos Sanitarios (AEMPS). The AEMPS, after approval of the protocol by Comité de Ética de la Investigación con Medicamentos (CEIm) del Hospital Universitario La Paz de Madrid,, has issued the pertinent authorizations for its implementation. Biological samples from the participants will be sent to this center for the determination of antibodies and neutralizing antibodies against SARS-CoV-2 as an indicator of protection against COVID-19.

Logo Vector Hospital Universitario La Paz
Logo Vector Hospital Clinico San Carlos 1
Hospital Vall D Hebron
Baixa 2

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