If you believe you were injured by any of the 16 vaccines covered under the National Vaccine Injury Compensation Program you must have symptoms of the claimed injury lasting at least six months to be able to file a claim for compensation in the program.
There are two exceptions which permit a vaccination injury claim to be filed without a person having met the residual six months of symptoms requirement, hospitalization with surgery to correct the claimed vaccination injury, and/or vaccination related death.
Never delay seeking out medical care if you think you were injured by a vaccine as some vaccine-related injuries can be life threatening and healthcare providers are trained to recognize and treat serious illnesses. From a vaccine injury claim perspective consulting with a healthcare provider soon after symptom onset can help provide objective verification of when symptoms started, and ongoing treatment encounters serve to show the extent and duration of the injury in question as well as the resolution of symptoms.