Multiple experts recently explained why people feel symptoms after they get the second shot of the COVID-19 vaccine.

What’s going on?

The COVID-19 vaccine continues to roll out. But people have reported feeling symptoms of a cold — fever, fatigue and more — after getting a second shot. Experts want to calm fears over those symptoms, though.

NBC News medical contributor Dr. Kavita Patel told that the symptoms are expected.

  • “The second vaccine (dose) — think of it as having that hit to your immune system, and your immune system now recognizes the vaccine, so it does its job,” she said . “... I felt, for about 36 hours, like I had the flu.”
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Dr. Bill Moss, a pediatrician and professor of infectious disease epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, also explained to how the second dose impacts the body.

  • “The second dose is really like a booster dose,” he said. “The immune system is seeing the vaccine for the first time with the first dose and is reacting to that, and the cells of the immune system are recruited to kind of recognize that spike protein (the part of the coronavirus that the vaccine affects). So when the body’s immune system sees (the vaccine) a second time, there are more cells and there’s a more intense immune response, resulting in those side effects.”

What to expect

Dr. Amanda Cohn, a member of the CDC’s National Center for Immunization and Respiratory Diseases, recently explained what people can expect from the second dose.

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  • She said people may experience “pain, potentially fatigue and a low-grade fever” from the vaccine.
  • These side effects are “expected and should resolve after one or two days,” she said.
  • Cohn said the side effects are “not COVID. It’s your body building an immune response to the protein that is mimicking the disease.”

There are a lot of people who have also reported a rash on their arm after getting the Moderna COVID-19 vaccine, according to CBS Minnesota. That symptom has now been called “COVID arm,” which is also normal.

  • “We’ve seen reactions like this even with other vaccines,” Dr. George Morris told CBS Minnesota. “We know, when you get a flu vaccine, many people will have a local reaction in their arm. Tetanus vaccines. Shingles vaccines.”