The CDC says people who received the Moderna coronavirus vaccine were more likely to experience mild side effects than those who received Pfizer’s.
The study documented episodes of injection site pain, fatigue, itching, and headaches, but it did not include serious allergic reactions.
About 74% of Moderna recipients reported episodes after the first shot, while just over 65% of Pfizer recipients reported side effects.
After the second dose, 82% of Moderna recipients reported an adverse reaction and over 68% of Pfizer recipients also saw a reaction.

Side Effects from Moderna:
In the arm where you got the shot:
Pain
Redness
Swelling

Throughout the rest of your body:
Tiredness
Headache
Muscle pain
Chills
Fever
Nausea

These side effects usually start within a day or two of getting the vaccine. They might feel like flu symptoms and might even affect your ability to do daily activities, but they should go away in a few days.
Also, side effects could also vary depending on whether or not you’ve had coronavirus. According to the health department, it’s called “the booster effect.” People who have already had COVID will report some side effects because the vaccine is acting a little bit like a booster dose to their immune system. Basically, the immune system has already learned how to protect itself from the virus.

Younger People Are More Likely to Experience Side Effect
Chicago’s top doctor, Chicago Department of Public Health Commissioner Dr. Allison Arwady, broke it down Thursday, saying in Facebook Live that younger people are more likely to experience side effects “because younger people have more robust immune system broadly.”

And, according to Loafman, the body’s immune system is what creates the symptoms.

“That’s simply a reflection of the immune response, just the way we have when we get ill,” he said.

Women Are More Likely to Report Side Effects
Arwady noted that women are more likely to report side effects than men.

“Some of this is because women may just be better reporters… but there probably is something real to this too because something else interesting for those who may not know as much about immunity is that autoimmune diseases? Much, more likely in women, too,” Arwady said. “And even the, like, more serious like the allergic reactions, the more serious allergic reactions? More likely in women.”