evidence: Mild-to-moderate constitutional symptoms such as fever, fatigue, headache, or muscle aches are common in the first 24 to 48 hours following vaccination and are not suggestive of VITT. Patients with severe, recurrent, or persistent symptoms from 4 to 42 days following COVID-19 vaccination, including intense headache, abdominal pain, back pain, nausea and vomiting, vision changes, change in mental status, shortness of breath, leg pain and swelling, and/or bleeding/petechiae, should be evaluated urgently by a medical provider, and consideration given to underlying VITT. The peak time period for initial symptoms is days 6 to 14. [...] - See I et al. US Case Reports of Cerebral Venous Sinus Thrombosis With Thrombocytopenia After Ad26.COV2.S Vaccination, March 2 to April 21, 2021. JAMA. 2021 Jun 22;325(24):2448-2456. doi: 10.1001/jama.2021.7517. PMID: 33929487; PMCID: PMC8087975. [...] - Schultz NH et al. Thrombosis and thrombocytopenia after ChAdOx1 nCoV-19 vaccination. DOI: 10.1056/NEJMoa2104882.