Neurological Immune-Related Adverse Events After COVID-19 Vaccination: A Systematic Review

The coronavirus disease 2019 (COVID-19) pandemic has affected millions of individuals worldwide. The global scientific effort to design an effective vaccine against this virus has led to the development of several vaccine candidates. The expedited rollout of these vaccines has created some public distrust regarding the safety of these new vaccines. This review compiles clinical data from reports of diagnosed immune-related neurological events that have occurred after COVID-19 vaccine administration with the exception of those secondary to hematological abnormalities. A systematic literature search was performed, using several databases, to identify reports of postvaccination adverse neurological events. The search resulted in 18 studies that met our criteria. These studies included 61 patients who had received COVID-19 vaccines and experienced at least 1 neurological adverse effect. The most common neurological event was facial nerve palsy (50% of all events). Other less frequently reported events included the reactivation of herpes zoster, Guillain-Barre syndrome, other demyelinating diseases, and neuropathy. The underlying mechanism was hypothesized to be related to vaccine-induced type 1 interferon production leading to decreased tolerance of the myelin sheath antigens. Other hypotheses include vaccine-induced transient lymphopenia and immune dysregulation. Most of the reported events were time limited and resolved spontaneously. Given the rarity of reported neurological events compared to the total number of vaccines administered, and the similarity in the incidence of events between COVID-19 vaccines and other more common vaccines, there is little evidence to support a causal relationship between COVID-19 vaccines and adverse neurological events.