Pfizer and Moderna: is there a difference?


Pfizer and Moderna: is there a difference? Is it ok to get 2 different mRNA vaccines for my COVID-19 series?


If you received an mRNA vaccine for your first dose, it is likely that you will receive the same vaccine for your second dose. However, BC receives the COVID-19 vaccines in quantities based on a nationally coordinated process, and you may be offered a different brand of vaccine that is the same ‘type’ (i.e., mRNA) as your first dose.

So, here is some information to consider. 

The Pfizer and Moderna COVID-19 vaccines are very similar – they are both very effective, very safe, and well studied.

They are both mRNA vaccines and so work the same way. They both provide instructions via messenger RNA to teach your body's immune system to recognize the COVID-19 virus so that you can fight off infection if the real virus enters your body in the future. Both vaccines generate antibodies against the spike protein of the SARS-CoV2 virus, which is the virus that causes COVID-19. The vaccines do not contain the virus itself.

Both vaccines are very effective in protecting against COVID-19 illness. In large scientific studies, both vaccines were found to be about 95% effective in preventing COVID-19 illness after 2 doses.

Both vaccines have similar side effects which are mild and temporary. The most common possible side effects include shoulder/arm pain at the site of injection, body and muscle pains, chills, feeling tired and feeling feverish. These side effects typically improve in about one to three days. Both vaccines are injected into the upper arm – very quickly and with very little discomfort. One vaccine is not more painful than the other.

There are lots of examples in medicine where we substitute one medicine for another because they work the same way. An example is Motrin and Advil.

Interchanging vaccines is not a new idea. Similar vaccines from different manufacturers  are  routinely  used  interchangeably,  including  vaccines  for  Hepatitis  A,  Hepatitis  B, and Measles, Mumps, Rubella (MMR).  General vaccine principles say that to be considered interchangeable,  vaccines should  be authorized with the same indications and with similar schedules, for the same population, contain or produce comparable type(s) of antigen, and be similar in terms of  safety, side effects, immunogenicity and effectiveness.  Having one Pfizer and one Moderna is safe and effective!

When comparing Moderna and Pfizer-BioNTech remember:
✔ They are the same type of vaccine.
✔ They have the same levels of safety and effectiveness.
✔ They both use mRNA as the active ingredient.

Canada's National Advisory Committee on Immunization says that when the same mRNA vaccine product is not readily available, or is unknown, another mRNA COVID-19  vaccine product recommended in that age group can be considered interchangeable and should be offered to complete the series. So, our advice is to take whichever one is offered to you, knowing that they will both protect you and the people you love from getting sick from COVID-19.

Date last reviewed: 
Saturday, Jul 10, 2021