Central nervous system adverse events after ChAdOx1 vaccination

Post-ChAdOx1 vaccine (AZD1222) adverse events following immunization (AEFI) are uncommon. Recently described neurological events include thrombocytopenia with thrombosis syndrome (TTS) with cerebral venous thrombosis and Guillain-Barré syndrome. There are very few AEFI reports following COVID vaccination from India, because of underreporting or other factors. A few cases of acute transverse myelitis (ATM) and post-vaccinal encephalitis have also been reported.

Over 11 months, in 2 districts of Kerala, India, 8.19 million people were vaccinated with the ChAdOx1 vaccine.

During this period, we encountered five cases of autoimmune central nervous system (CNS) AEFI following ChAdOX1 (Oxford/AstraZeneca, Covishield™) vaccination. These included three cases of acute disseminated encephalomyelitis (ADEM), one case of opsoclonus myoclonus ataxia syndrome (OMAS), and one case of limbic encephalitis. The calculated crude incidence of post-ChAdOX1 autoimmune CNS AEFI was approximately 0.24 cases per million for encephalitis and 0.36 per million for ADEM. This was compared to the crude annual incidence of community-acquired ADEM worldwide (3.2-4 per million) and the crude annual incidence of community-acquired encephalitis in India (8.35-10 per million).

There was no increase in the incidence of post-vaccination CNS AEFI (ADEM or encephalitis) as compared to the community incidence of ADEM or encephalitis. While this emphasizes the safety of ChAdOX1 nCoV-19 vaccination for COVID-19, it is important to recognize these post-vaccination autoimmune syndromes early to initiate immunosuppressive therapy.