COVID-19 Vaccine Hot Topics: Your second dose and adverse reactions



A message from Dr. Helena Swinkels, Office of the Chief Medical Officer; and Marion Guenther, Community Nursing Service - Immunization


With the arrival of COVID-19 vaccines, we're seeing the light at the end of the tunnel. We still have steps to take before we're all clear, however – starting with actually getting vaccinated! Happily, many First Nations people in BC, including First Nations physicians, have already taken this step. See Taking a shot at COVID-19 – an FNHA Doctor’s vaccine account.

As part of the FNHA's commitment to keep you informed about vaccines, this week we are answering two of the questions we receive most often.

Q: How far apart should I get my two doses?

A: The second dose can be delayed up to six weeks with no concern.

The COVID-19 vaccines from Pfizer-BioNTech and Moderna are recommended to be given in two shots at around three and four weeks apart. However, the vaccines will sometimes need to be given a little further apart if there are shipment delays, or to make sure as many people as possible can get a first shot. This would happen when vaccines are in short supply and transmission of the virus is high.

The World Health Organization (WHO) allows for the second shot to be given up to six weeks (42 days) after the first in these situations. We know from experience with other vaccines that the body produces a strong, long-term immune response after a second shot, even if this is delayed. The Pfizer and Moderna vaccines are up to 92 per cent effective after one dose (as found in recent studies done in BC) and 94–95 per cent effective one to two weeks after both doses.

We will endeavour to provide the second dose as close to the six-weeks / 42-days mark as possible, as we don't know yet how long protection lasts after only one shot. It is very important to get both shots to ensure a high level of protection that lasts. 

Q: What do I do if I experience an adverse reaction?

A: Serious reactions are rare, but it's best to know what to do if you have one. 

The first kind of reaction that we are concerned about from any vaccine or medicine is an allergic reaction. Symptoms of an allergic reaction include: 

• hives (bumps on the skin that are often very itchy);

• swelling of the face, tongue or throat;

• difficulty breathing.​

While these occur very rarely, they can be very serious; this is why you must wait at least 15 minutes before you leave the clinic or pharmacy after receiving the COVID-19 vaccine and longer if you have a history of allergies. Our staff have the training and medications required to respond to a serious allergic reaction. 

Other reactions that can happen after a vaccine occur because your immune system is working to respond to the vaccine. These kinds of minor side effects are observed with both the Pfizer-BioNTech and Moderna vaccines, similar to ones you might get from any shots. People can experience pain in the arm where they had the injection, tiredness, headache, muscle pain, chills, joint pain and low-grade fever. These reactions are usually mild and last a few days, and they can be worse after the second dose. 

Let your health care provider know right away about serious or unusual symptoms, such as fever over 40 Celcius (104 Fahrenheit). They will let you know what to do to feel better and whether further investigation is needed. 

All serious or unusual reactions are also monitored across Canada to make sure vaccines are safe. For more information on adverse events following immunization, see Side Effects​ on ImmunizeBC.​

For all questions pertaining to the COVID-19 vaccines, our FAQ is updated regularly, while our COVID-19 portal provides resources for BC First Nations individuals, community leaders and health professionals.

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