What's Really Happening If You Get The Chills From The COVID-19 Vaccine

Getting a COVID-19 vaccine is meant to protect you against the disease and all the unpleasant and even life-threatening symptoms that come along with it. So what happens when you get vaccinated and you find yourself suffering from a fever and chills anyway? Experts say there's a reason for this type of reaction, and it's actually a good thing, according to Bustle

When you're injected with the COVID-19 vaccine, your body immediately recognizes that there's something floating around in there that doesn't belong. So your immune system gets busy producing antibodies that will help defend you from infection if you ever get exposed to the virus that causes COVID-19. The problem is, your body thinks it's defending you from an actual virus, not just harmless parts of a virus that the vaccine is teaching your body how to make. Because of this, your immune response may be strong as your body fights off what it thinks is a threat.

Your internal thermostat is to blame

One of the possible side effects of the COVID-19 vaccine is chills, says the Centers for Disease Control and Prevention (CDC). This uncomfortable shaking often accompanies the feeling that you're freezing, even if you actually have a fever. So why would your body shake and feel cold if you're really burning up? Think of your body's response to the vaccine as a heating system in a house. When your immune system wants to kill off a virus, one of the ways it does this is to tell your body to turn up the temperature. Your internal thermostat gets set higher. Now your body knows that it needs to get warmer, but it hasn't caught up yet to the new set temperature. So it "turns up the heat" by shivering, essentially small muscle contractions meant to produce more heat and increase your temperature. Your brain knows that your body temperature is supposed to be warmer, but also registers that its temperature isn't high enough yet, so you feel cold.

While it might not make you feel better in the moment to know that your chills are a good sign that your body's immune system is working hard, it's helpful to know that the side effect is normal. It's even possible these symptoms will be more intense after the second shot in a two-part vaccine series since your immune system is already primed. If your side effects don't disappear after a few days, contact a healthcare professional.