Neurological Conditions Following COVID-19 Vaccinations: Chance or Association?

Coronavirus disease 2019 (COVID-19) has been labeled a global pandemic with the first reported case of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurring in Wuhan, China in December 2019. To combat the alarming, increasing rate of those affected by the virus, vaccine development ensued. As mass vaccination initiatives against COVID-19 ensued, adverse reactions began emerging. This non-consecutive, population-based case series focuses on four vaccine-associated neurological adverse events across the central and peripheral nervous system detailing the diagnosis, treatment and subsequent follow-up management. These four patients presented to public and private hospitals in Trinidad and Tobago with new-onset neurological diseases soon after their first doses of a COVID-19 vaccine: two after the Pfizer-BioNTech vaccine (one case of new-onset seizures and one case of longitudinally extensive transverse myelitis) and two after the ChAdOx1 nCoV-19 vaccine (one case of Guillain-Barre syndrome and one case of meningitis-retention syndrome). The background incidence rates of neurological conditions in the population and the large numbers of persons being vaccinated means that some of these conditions will appear in the post-vaccination window by chance. Hence, establishing causal links is difficult. The close temporal relationship between vaccination and the presenting symptoms, the biological plausibility, and the extensive diagnostic workup to exclude other causes fulfill criteria provided by the World Health Organization for causality assessment of an adverse event following immunization on an individual level. On this basis, it was determined that these adverse events were likely due to the vaccines. However, establishing causal links on a population level requires large epidemiological studies and cannot be done on individual case reports alone. While physicians should be cognizant of even these rare adverse events of vaccines, it should be reiterated that the overall safety profile of vaccines is well established.