A framework for the post-authorisation safety monitoring and evaluation of vaccines in the EU: Study protocol for the occurrence of flares of Graves´ disease, Hashimoto´s thyroiditis, polyarteritis nodosa, autoimmune hepatitis, rheumatoid arthritis, psoriatic arthritis, multiple sclerosis, erythema nodosum, systemic lupus erythematosus, and ulcerative colitis using electronic healthcare data sources.