Ask Your Pharmacist

May 07, 2021

What are some of the common questions you get asked regarding COVID-19 immunizations?


New Brunswickers are asking lots of questions about the vaccines available against COVID-19. It takes quite a bit of time for pharmacists to answer your questions, but please keep asking us! Pharmacists understand, now more than ever, that immunization is a very personal decision, and your comfort with getting the jab is based on our ability to answer your questions to your satisfaction. We promise to continue to provide accurate and evidence-based information, in a way that is easy to understand, as it becomes available to us.  

When vaccines first became available, many patients asked us whether or not they should get vaccinated and whether they could be confident the vaccine is safe given its newness. Now that more information is available on those questions, people are better able to quantify the benefits and risks of immunization, and their questions have moved away from whether or not to get the vaccine to specific questions about the vaccines themselves. I have included answers to a few below:

1. If I receive my first COVID-19 dose with the Oxford – Astra Zeneca Vaccine, does this mean I must receive the second dose with the same vaccine?

Presently, the answer to this question is, yes. New Brunswick Public Health currently states that New Brunswickers will be offered a second dose of the same vaccine they received for their first dose. That said, Health Canada is evaluating ongoing clinical trials in the UK and Canada which may provide insight into the possibility of mixing first and second doses of COVID-19 vaccine. The ability to mix and match vaccines has definite advantages, including flexibility, especially given the challenges with vaccine supply we’ve experienced in Canada. There are theoretical benefits to administering a second dose of vaccine that works by a different mechanism than that of the first dose. Also, this may allow for an alternative for younger people that received a first dose of Astra Zeneca vaccine that, with the knowledge now known about clot risk, may not be appropriate to receive this second dose. Based on Health Canada’s evaluation of ongoing studies, NB Public Health will make an informed decision about second immunization doses. 

2. If the original studies were done giving the second dose at 21 or 28 days, how is it okay for New Brunswick to give the second dose 14 weeks after the first?

NB Public Health made this decision to ensure that as many New Brunswickers as possible receive their first dose of COVID-19 immunization as quickly as possible. The best way to protect each New Brunswicker, is to have as many of us as possible in the population receive the vaccine; it’s a “Where we go one, we go all” mentality. Preliminary studies show that the level of protection against COVID-19 stays high for at least two months following immunization. Based on science and experience with other vaccines we know that vaccine effectiveness gradually wanes with time. Given that all COVID-19 vaccines currently on the market are highly effective, even if their effectiveness wanes somewhat by 14 weeks, they are still likely to provide a high degree of protection against COVID-19 until the second dose is administered.

3. How soon after the COVID-19 immunization will I begin to have protection against the virus and will the vaccines protect against the variants?

A significant degree of protection will occur approximately three weeks after immunization of the first dose, regardless of vaccine used. Vaccine effectiveness will be strengthened with the second dose, as will the duration of protection. It is important to remember that even when fully immunized against COVID-19, we can still get infected with the virus and we can still spread the virus.

All vaccines on the Canadian market are highly effective. Scientists believe that even in cases in which effectiveness is reduced by variant strains, existing vaccines will still be highly effective at preventing hospitalization, serious illness, and death from COVID-19.

By immunizing as many members of the population as possible we do our best to control the spread of the virus. It is important to continue to follow Public Health’s guidance to continue to clean our hands frequently, wear protective face masks when in public, and to maintain physical distance.

 Dr Kevin Duplisea (PharmD BSc. Pharm, BSc. ACPR) is a pharmacist at Sharp’s Corner Drugstore in Sussex, New Brunswick. His opinions expressed in this newspaper are published for educational and informational purposes only, and are not intended as a diagnosis, treatment or as a substitute for professional medical advice, diagnosis or treatment. Send your questions to