AstraZeneca admits Covishield's rare side effect TTS, causing blood clots with low platelets. TTS symptoms include severe headaches, abdominal pain. Treatment involves anticoagulation therapy, IVIG. "TTS is a serious and life-threatening adverse event. WHO has issued this interim emergency guidance to increase awareness about TTS in the context of COVID-19 vaccination and help healthcare providers in the assessment and management of potential TTS cases," the 2023 statement by WHO read.