(353) Serious Neurological Adverse Reactions to SARS-CoV-2 Vaccines in Chile

Background: SARS-CoV-2 vaccines could cause adverse reactions. The frequency, seriousness and temporality of these side effects may differ between type of vaccine and patient characteristics. Nervous system is the most commonly affected organ. Neurological side effects as cause of SARS-CoV-2 vaccines are limited known in Chile.

Objectives: To estimate the reporting rates of serious neurological adverse reactions associated with SARS-CoV-2 vaccines in Chile.

Methods: A retrospective cohort study was conducted in the database of the national center of pharmacovigilance of Chile between December 24th, 2020 (first SARS-CoV-2 vaccination in Chile) and July 2nd, 2022. The sample included spontaneous notifications of myelitis, Guillain-Barre syndrome (GBS), encephalitis, acute disseminated encephalomyelitis (ADEM), meningoencephalitis and meningitis associated with SARS-CoV-2 vaccines. All notifications were provided by health professionals. The main outcome was the reporting rate of mentioned serious neurological adverse reactions associated with SARS-CoV-2 vaccines. The secondary outcome was the causality of the adverse events. Each spontaneous notification was assessed by the national expert committee on pharmacovigilance according to the Brighton Collaboration case definition and the WHO causality algorithm. Data analyses were performed using STATA 15.1.

Results: A total of 115 clinical manifestations were described in 94 reported cases of serious neurological adverse events. The mean age was 41.1 ± 20.9 years, mainly women (54.3%). Of 115 clinical manifestations described, 38 (33.0%) included the term “encephalitis”; 37 (32.2%) “GBS”; 13 (11.3%) “myelitis”; 13 (11.3%) “meningoencephalitis”; 7 (6.1%) “ADEM” and 6 (5.2%) “meningitis.”
Finally, 52.1% (49) of reported cases met a case definition. A total of 59.6 million of doses were administered during the study period. The reporting rate of cases per 100.000 doses administered varied by type of vaccine between 0.008-0.015 myelitis; 0.008-0.218 GBS; 0.062-0.008 encephalitis; 0.062 meningoencephalitis; and 0.004 meningitis. Incomplete data were recorded for ADEM. A 65.3% of cases were “indeterminate” causality. Most of reported cases (54.3%) occurred after the first booster of vaccination.

Conclusions: The reporting rate of the studied neurological adverse reactions associated with SARS-CoV-2 vaccines in Chile were rare and very rare and varied by type of vaccine. GBS was de neurological complication with highest reporting rate among conditions studied. This study contributed to a better understanding of the safety of SARS-CoV-2 vaccines.