Health begins trial to test the effectiveness of giving Pfizer a second dose to people vaccinated with Astrazeneca

Health is promoting a new clinical trial after stopping vaccination with Astrazeneca in children under 60. For example, the Carlos III Health Institute has launched the “CombiVacs” study, which will assess the possibility of administering a dose of Pfizer vaccine to people who have only received a single dose of AstraZeneca.

It is expected to start next week and have final results by mid-May. This is a controlled, randomized and adaptive trial that will assess the safety and immunogenicity of this option, after the decision to vaccinate only those over 60 years of age with AstraZeneca due to the occurrence of thrombotic events in patients. children under this age.

A restriction which meant that many under the age of 60 who had already received a dose of AstraZeneca could not receive the second obligatory dose. For the moment, it will not be studied with the Moderna formula, although the possibility of including it in the future is open.

The director of the Carlos III Health Institute, Raquel Yotti, detailed that the trial will be carried out in five hospitals: La Paz in Madrid, the San Carlos clinic in Madrid, the Vall d’Hebron in Barcelona, ​​the Barcelona clinic . and the Cruces de Vizcaya. The National Microbiology Center, for its part, will participate as the central laboratory of the study.

“We have chosen these five hospitals because they have the capacity and the experience to do it with the urgency that we need”, said Jesús Antonio Frías Iniesta, coordinator of the clinical research network of the Institute of health Carlos III and head of the clinical pharmacology service. of the University Hospital of La Paz.

Yotti said it was “one of the first clinical trials that will analyze the safety and immunogenicity of this type of combined diet.” The scientific evidence generated will be of great value to the Spanish health authorities, and most likely at the international level, ”he stressed.

A clinical trial with 600 patients

Frías Iniesta has argued that 600 patients from different age groups and regions of Spain who have received a single dose of AstraZeneca will be recruited. They will be divided into two groups: one of the 200 who will receive the dose “immediately” and another of the 400 who will receive it after 28 days. After receiving the vaccination, they will be evaluated at three, six and twelve months to check for effects. The aim is to start the trial “quickly”: “If possible, start it next week”.

According to ISCIII expert, the goal is to have a conclusion before the 12 weeks between the first and second dose of AstraZeneca have elapsed, to face the vaccination with this group with more scientific evidence .

Peace of mind for people vaccinated with AstraZeneca

The head of the Department of Medicines for Human Use of the Spanish Agency for Medicines and Health Products (AEMPS), César Hernández, issued a “message of tranquility” to people waiting for the second dose: “Do not worry The level of protection will be maintained, it does not run out in a day. ”

The AEMPS expert stressed that in this 12-month window, “this evidence will be developed that will be able to support decision-making to continue the campaign.” It was already known that this second dose could be spaced up to 12 weeks apart. , but that does not mean that all patients in the clinical trials received the doses exactly at 12 weeks. Some even up to five months later, “he reassured.

Thus, he insisted that they are “calm enough” that the immunity generated during these 12 weeks “can be maintained and the population is protected” against symptomatic COVID-19, hospitalization and the death. “This opens the window of opportunity for a study that gives us the best evidence. In addition, the availability of vaccines is increasing, we are not facing an emergency,” he added.

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