Covid-19 vaccines may cause mild side effects, experts say, stressing need for education, not alarm

While the world awaits the results of large clinical trials of Covid-19 vaccines, experts say the data so far suggest one important possibility: The vaccines may carry a bit of a kick. In vaccine parlance, they appear to be “reactogenic,” meaning they have induced short-term discomfort in a percentage of the people who have received them in clinical trials. This kind of discomfort includes headache, sore arms, fatigue, chills, and fever. As long as the side effects of eventual Covid-19 vaccines are transient and not severe, these would not be sources of alarm — in fact, they may be signals of an immune system lurching into gear. It’s a simple fact that some vaccines are more unpleasant to take than others. Think about the pain of a tetanus shot, for instance.