You may experience temporary side effects — injection-site reactions, fatigue, fever, headache, swollen lymph nodes, and muscle aches and pain — from the COVID-19 vaccines currently authorized for emergency use in the US. We know people tend to report more intense side effects from the second dose of the mRNA-based Pfizer and Moderna vaccines. This is because the body is already primed and building an immune response after the first dose of these shots. Similarly, people who have been sick with COVID-19 could exhibit stronger side effects from their vaccine dose because their immune systems were previously introduced to the virus and have some form of immunity (one study found immunity lasted for up to eight months postvirus, though research varies).
Sabrina Assoumou, MD, MPH, an infectious-diseases physician at the Boston Medical Centre and an assistant professor at Boston University's School of Medicine, reiterated to POPSUGAR that if people had COVID-19, they may exhibit more symptoms to the vaccine since "they've already had that prime" with the virus. As for the side effects, the body is doing what it's supposed to be doing: "It's learning, it's making those antibodies that are going to protect you."
Antonio Crespo, MD, an infectious-disease expert at Orlando Health, agreed. "Your body already has been exposed," he told POPSUGAR, speaking about people who previously had COVID-19. "And now it's reacting a little bit more violently to the exposure."
How you react to the vaccine may depend on age as well, and experts note that side effects exhibited are short-lived; contact your doctor if your symptoms do last longer than a few days or if they become severe. Remember, the symptoms experienced are not contagious, and you are not considered fully vaccinated by the CDC until two weeks have passed since a single-shot vaccine or second dose of a two-dose vaccine.
POPSUGAR aims to give you the most accurate and up-to-date information about the coronavirus, but details and recommendations about this pandemic may have changed since publication. For the latest information on COVID-19, please check out resources from the WHO, the CDC, and local public health departments.