The COVID-19 vaccines have a series of typically mild side effects, including soreness at the injection site, swelling, fever, headache, fatigue and muscle aches.
If you’re experiencing these symptoms after getting a COVID-19 vaccination, does that mean the vaccine is working to protect you in the future?
According to Dr. Richard Kennedy, a professor of medicine at Mayo Clinic and the co-director of the Mayo Clinic Vaccine Research Group, the answer is yes — side effects mean your immune response is kicking in response to the vaccine. But the initial symptoms you feel are only half the story.
Here’s how it works: Your immune system has two different components — innate immunity and adaptive immunity. Innate immunity is your body’s first-line response to an outside invader.
“Innate immunity does the same thing every time it sees a microorganism in your system. It’s got to recognize that you’re infected, sound the alarm and start the adaptive immune response,” Kennedy said.
“Innate immunity does those first two things very well. It’s not very good at protecting you against viral infections,” he continued. “It’s more of a speed bump to slow it down.”
After your body’s innate response, which occurs at the first sign of an infection or virus, adaptive immunity takes over. This kind of immunity is responsible for the creation of B and T cells, which can blast away infection.
Though the current vaccines do not contain live viruses, they do trigger your immune responses to protect you. When you receive a vaccine, your innate immunity is stimulated first, which can lead to soreness, heat, fatigue, muscle aches and headaches, which should dissipate within a few days.
Within a week-and-a-half or so, your adaptive immunity starts firing, offering you actual protection from the virus.
“It’s like your immune system has a two-step approach,” Kennedy says. “The first one is all the side effects you’re getting from a vaccine, and the second one is making T cells and B cells and actually protecting you from the virus.”