A new study has an encouraging message for Americans who shy away from Covid shots because of worries about side effects: The chills, fatigue, headache and malaise that can follow vaccination may be signs of a vigorous immune response.
People who had those side effects after the second dose of a Covid vaccine had more antibodies against the coronavirus at one month and six months after the shot, compared with those who did not have symptoms, according to the new study. Increases in skin temperature and heart rate also signaled higher antibody levels.