Get on it quick and all will be well, if there's any serious damage, you have a limited amount of time to make a vaccine injury claim.
A mycoplasma infection from the vaccine. Sometimes "dead" bacteria used to make the vaccine have a still alive mycoplasma deep inside them. Once the dead bacteria are injected, they are rehydrated and opened up by the immune system, releasing the mycoplasma to start an infection. Up to 5% of vaccines are still contaminated with these pests that are very hard to keep out of cultures. You won't find many standard labs that can test for it. Google Dr. Garth Nicholson, his lab does testing.