answersLogoWhite

0

Because the vaccine contains the virus that your body will react to and that immune response is exactly what the vaccine is for...but at the same time it can make a local reaction at the site of injection as the immune system starts attacking the virus in the vaccine there. Your body thinks that spot is infected and so, like with any infection, the area gets red, sometimes hot, swollen, and painful, but it should only last a day or two. Use your arm as usual, that will help it get better faster. Some people don't have any soreness at all and others get so sore they don't want to move the arm...moving it is what will make it better quicker, though.

User Avatar

Wiki User

14y ago

What else can I help you with?