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.