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ComPaRe study: one in twelve patients hesitant to be vaccinated changes their mind after consulting information on the benefits and risks of vaccines

11 Aug 2021 | By Inserm (Newsroom) | Covid-19


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The team from the Clinical Epidemiology Center of Hôtel-Dieu AP-HP Hospital, Inserm and the University of Paris, coordinated by Professor Philippe Ravaud, has developed an online tool for viewing the benefits and the risks of vaccination against Covid-19. Presented to a sample of chronic patients from “ComPaRe”, the Community of Patients for Research created by the AP-HP and the University of Paris, the team measured how many of them, previously undecided about their vaccination, have changed my mind after using the tool. This work was published on July 31, 2021 in BMC Medical Informatics and Decision Making.

Convincing the hesitant population to get vaccinated is a matter of major concern in the fight against the Covid-19 epidemic.

According to a study recently published in the Lancet Public Health 1 , around 30% of adults in France would categorically refuse the COVID-19 vaccination, and 9 to 40% are hesitant. The main reasons for refusing vaccination are concern and demand for further hindsight regarding the safety and efficacy of vaccines.

In January 2021, the team from the Clinical Epidemiology Center of Hôtel-Dieu AP-HP Hospital, Inserm and the University of Paris, developed an online tool measuring the benefit / risk of vaccination. In particular, it makes it possible to visualize the risk of death, hospitalization and long-term COVID with and without vaccination, as well as the serious adverse effects of vaccination, depending on the age and sex of the person.
The data used come from published scientific publications, freely accessible on the internet. The data concerning the efficacy and safety of the vaccines which were used to construct the tool come from the clinical trials which led to their marketing authorization.

3,152 patients from the Community of Patients for Research (ComPaRe) participated in the evaluation of this tool. The research team asked participants to indicate their intention to be vaccinated before and after viewing the tool. By comparing patient responses before and after, she was able to determine the influence that visualizing the benefits and risks of vaccines could have on patient decisions.

Before consulting the tool, 1,952 (62%) patients declared that they wanted to be vaccinated, 961 (30.5%) preferred to wait until they had more information on the efficacy and safety of vaccines before being vaccinated and 239 (7.5%) did not want to be vaccinated.

After consulting the tool, 96 of the 1,200 people initially reluctant to vaccinate had changed their minds. On average, for every 12 people reluctant to get vaccinated, one person changed their mind after consulting the tool.

The tool has been online on the government website since May 2021 . Used by more than 125,000 people, it has been updated with data from the Janssen vaccine and supplemented with data on the risk of thrombosis after the AstraZeneca vaccine.


Created in 2017 by the AP-HP and the University of Paris, ComPaRe, the Community of Patients for Research today brings together nearly 45,000 patient volunteers across France.

On this occasion, ComPaRe renews its call for participation in order to bring together 100,000 patients to contribute online to medical research on its site .

Participants help advance research on their chronic disease (s) by regularly participating in scientific studies and answering researchers’ questions via the secure platform .

Patients participate in the general cohort and / or one of the 13 cohorts dedicated to diabetes, Verneuil’s disease, vitiligo, chronic low back pain, kidney disease, vasculitis, arterial hypertension, endometriosis, asthma, COPD, Marfan syndrome, neurofibromatosis and long Covid.

And new cohorts are being formed.

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Impact of an interactive web tool on patients’ intention to receive COVID-19 vaccination: a before-and-after impact study among patients with chronic conditions in France.

Tran, VT., Sidorkiewicz, S., Péan, C. et al.

BMC Med Inform Decis Mak 21, 228 (2021).