Vaccination against COVID-19 appears to be essential to control the pandemic. Vaccination response and duration of immunity vary greatly among individuals, and age appears to be a major factor.

We hypothesize that probiotic intake around the time of vaccination may play a role in the vaccine response. The aim of this study is to compare the antibody level of elderly people between 65 and 89 years of age after vaccination, according to the intake (or not) of probiotics.

The results of this study may provide recommendations for the use of probiotics in seniors who are about to receive a booster dose of the COVID-19 vaccine.

The study is a collaboration between the University of Sherbrooke and Laval University, and is funded by the Canadian Institutes of Health Research.

A clinical trial is a study that evaluates new ways to prevent, detect, treat or manage a disease. Treatments used in medicine are based on the results of clinical trials.

A clinical trial is research in which people freely agree to participate.

Participants in the study must meet all the following criteria:

• Be between 65 and 89 years of age

• Have already received 3 doses of the COVID-19 vaccine, the last of which was more than 3 months ago

• Have not contracted COVID-19 in the past three months

• Live in Quebec

If you wish to participate in our study, other criteria will be validated with you during a telephone call with a member of our team.

• You will contribute to improvement of the knowledge of vaccination and immunity to COVID-19

• You may benefit personally from participating in this research project (such as increasing your immune response to COVID-19), but we cannot guarantee it at this moment.

The disadvantages of the project are mainly related to the collection of samples (possible discomfort, embarrassment, time commitment, slight pain on your fingertip for blood samples), but they are generally well accepted. In order to ensure safe sampling, clear and detailed instructions will be given to participants.

According to the WHO, “live microorganisms which when administered in adequate amounts confer a health benefit on the host.”

There are no Health Canada warnings about taking probiotics and several studies suggest that their use is beneficial to the immune system.

Taking probiotics has very few undesirable side effects, unless you take more than the recommended dosage (bloating, intestinal irritation, constipation). However, there could be currently unknown risks related to taking the product under study.

A placebo is a substance with no active ingredient. Therefore, it has no pharmacological effect on the pathology it is supposed to treat. That said, a placebo can have beneficial effects on the patient, but rather through psychological or physiological mechanisms.

The placebo used in our study will look the same as the probiotic product and will contain the same non-medicinal ingredients (sugar-like substance).

Whatever product you receive will be determined randomly. Neither you nor the research team will know if you have received the placebo or the probiotics before the end of the trial.

This is called a double-blind study. At the end of the trial, this will allow us to objectively compare the results of the two groups. If the results of the "probiotics" group are better than those of the "placebo" group, we will be able to conclude that the probiotics tested have a greater effect than the placebo.

Taking a dried blood sample involves pricking your finger with a small needle, putting a drop of blood on a provided piece of cardboard, and letting it dry for a few hours. The prick may be uncomfortable, but it is usually not painful.

The study entails for 5 dried blood samples to be taken and returned by mail. All collection instructions are provided in the PIRATES-COV kit.

A stool sample is simply a small amount of stool (about a teaspoon) transferred to a sterile container.

For the study, only one stool sample is required. It is to be self collected at home and sent to us by mail. All collection instructions are provided in the PIRATES-COV kit.

Yes, participants will receive financial compensation. This compensation is conditional on the completion of all the steps and samples related to the study. All the details will be communicated to you during the first phone call with our team.

If you agree to travel to the CHUS for blood sampling (optional), you will also receive compensation for your travel and parking expenses.

To protect your identity, all data collected (including personal information and samples) will be kept confidential to the extent permitted by law.

Specifically, you will be identified by a code number (not your name), and the key linking your name to your research file will be in the sole possession of the researcher assigned to that research project. In addition, your samples will be destroyed after the retention period determined in the study framework.

You have the right to request the deletion of this data at any time.