Why do some vaccines require more than one dose?

Why get vaccinated?

The discovery of vaccination revolutionized the medical world. Since then, several deadly diseases have even disappeared from the face of the earth.

Vaccines are a safe way to build immunity to certain diseases. The principle is to introduce an inactivated or attenuated pathogen to allow the immune system to recognize the disease and prepare for a future invasion. The antibodies produced will allow the host to eventually defend itself.

One of the main principles surrounding vaccination is herd immunity. This concept refers to the fact that the more people who are vaccinated, the lower the risk of an epidemic. In other words, by getting vaccinated, we protect ourselves, but we also protect others.

One dose or multiple doses?

Some vaccines require more than one dose according to their vaccination schedule. Why do they require more than one dose? The number of doses is established according to the studies made during the development of the vaccine. Indeed, it is possible that one dose does not create sufficient immunity or does not last long enough. It is therefore recommended that more than one dose be administered. The interval between doses will also be determined during these studies.

Among the vaccines that require more than one dose, we can think of vaccines against:

• Hepatitis A 
• Hepatitis B
• Shingles
• HPV
• Meningitis
• Diphtheria, Pertussis and Tetanus

What about booster shots?

Sometimes the immune system needs a booster in order to respond adequately to a potential threat. Certain vaccines require booster doses after a certain period of time to maintain their effectiveness. Usually, one booster dose is sufficient, but the situation may vary from one vaccine to another. Your healthcare provider can advise you on the number of doses you should receive by consulting the medical literature and expert opinions.

Influenza is an example of a vaccine that requires an annual booster. In this case, the vaccine composition will differ depending on the predictions of the strains that are likely to be circulating that year.

How do I know if my vaccination is up to date?

Your healthcare professional (doctor, pharmacist or nurse) can analyze your vaccination status. In Québec, there is a registry that records everyone's vaccination information. By consulting it, your healthcare provider can determine which vaccines would benefit you and validate that all recommended doses have been received.

What if I haven't received all the doses I need?

Your healthcare provider will analyze your situation and can determine a vaccination schedule that will give you the best protection. Usually, there is no need to repeat the vaccination. You can simply continue where you left off.

The reference in vaccination in Québec: the QIP

The Québec Immunization Protocol is the reference on vaccination for health professionals in Québec. It covers recommendations, precautions and coverage criteria. Many vaccines are part of the Québec Immunization Program and are, therefore, free of charge for the patient under certain conditions. Your healthcare professional can tell you if you meet the coverage criteria for your booster doses.

Vaccines need to be planned

Before getting vaccinated at a Familiprix store, it is necessary to make an appointment. This way, your healthcare provider can validate your vaccination status in the Québec Vaccination Registry, order the necessary vaccines and plan the time needed for the appointment.

If you have any questions about vaccination or want to validate your vaccination status, don't hesitate to consult your healthcare professional.