We don’t all react the same way to a COVID-19 vaccine.
Some people get headaches or spend the day in bed. Some people might be up all night with chills. And some people might just have a sore arm – or feel nothing at all.
Thankfully, vaccine side effects, or the lack thereof, aren’t much of an indicator of how well a vaccine protects you against COVID-19, experts say.
“We’re all a little different and all our immune responses are a little different,” said Dr. Joanne Langley, a professor of pediatrics and epidemiology at Dalhousie University. “And we all have different sensitivities to the response.”
Normal side effects that you might experience after getting vaccinated include pain and soreness or redness around the injection site, aches and pains, fatigue and lethargy, she said.
Headaches, chills, fever and even nausea and vomiting are also relatively common side effects, especially after a second mRNA vaccine dose, according to a Government of Ontario fact sheet.
But what if you got none of these?
That’s what had Amanda Ferguson worried. Ferguson, who works for Toronto’s Sinai Health Foundation, participated in a research study, measuring antibody levels after her vaccine.
“Symptom-wise, I didn’t really have much of anything at all,” she said.
“I was really, really hoping for symptoms. I know most people aren’t, but because I have a compromised immune system, I wanted that sign that my body and my immune system was working. And other than a little bit of fatigue, I didn’t really feel much.”
Because she has Crohn’s disease and was taking an immunosuppressant drug, she was concerned that vaccines wouldn’t be effective for her, she said. And when she read a U.K. study showing that Crohn’s patients like her who took the drug Remicade didn’t produce many antibodies after their first dose of vaccine, she was upset.
“I was sobbing, I was absolutely sobbing because I thought this thing that had become a beacon of hope that was getting me through 15 or 16 months of isolation was all of a sudden taken off the table,” she said.
Even after the second part of the study came out, showing that two doses were effective, she still wondered, she said.
But her antibody test results put her at ease – even though she didn’t have much of a reaction to the shot.
“I wanted that sign that my immune system is working and it was nothing,” she said. “So then I had to wait another month, submit more blood tests, and then the results came back loud and clear that not only I had a good amount after the first shot, but then I had a really good number after the second.”
It’s true that inflammation, which can cause these annoying symptoms, is necessary to build up your immunity, said Earl Brown, a professor emeritus of virology at the University of Ottawa.
But, it doesn’t take very much.
“You need that inflammation. You need a certain amount of it. You don’t need enough to make you sick,” he said. “And so you’re not necessarily more immune if you’re put in bed for a day with your reaction versus those people who are out walking around with a with a sore arm.”
Producing antibodies is one way that the body builds immunity to a virus, he said. And because they’re relatively easy to measure through tests, it’s one of the ways that vaccine effectiveness has been assessed.
“The fact of the matter is that you don’t have to feel a strong reaction from the vaccine to be immunized,” Brown said. “But in practical terms, the vaccine has to stimulate inflammation that your body responds to. So you don’t have to feel unwell, but you have to have an activated immune system from your vaccine.”
If you do experience side effects following your COVID-19 shot, you can address the symptoms by taking medication for muscle pain, or resting if you feel tired, Langley suggested.
There are some possible very rare adverse reactions for which you should seek medical attention, she said. Things like changes in your level of consciousness, chest pain or extremely high fever should be looked into, she said. The Ontario government also recommends calling a doctor if you develop hives, swelling of the face or mouth, trouble breathing or numbness within three days of getting vaccinated.
The AstraZeneca vaccine is also associated with a very rare risk of serious blood clots and a condition known as capillary leak syndrome. Health Canada recommends seeking medical attention if you develop symptoms like sudden swelling of the arms and legs, feeling faint, chest pain or bruising in other places than the vaccine site.
But bottom line, if the vaccine didn’t make you sick, you shouldn’t worry, Langley said.
“I don’t think that people who haven’t had this really robust reaction after vaccine need to be concerned at all. The efficacy rates across everyone who has got the vaccine in the clinical trials and in the vaccine programs that are rolling out are all high.”
– With files from Jamie Mauracher, Global News