Participant-reported neurological events following immunization in the Canadian National Vaccine Safety Network-COVID-19 vaccine (CANVAS-COVID) study

Abstract

Introduction

The Canadian National Vaccine Safety Network (CANVAS) conducted active participant-based surveillance for adverse events following immunization during the COVID-19 vaccine campaign. This study evaluated the association between COVID-19 vaccination and neurological adverse events.

Methods

Participants were invited to complete online surveys to report health events that prevented daily activities and/or required medical attention within 7 days after COVID-19 vaccination or 7 days prior to the survey (unvaccinated controls); follow-up surveys were sent 7 months later. Neurological events were health events where the most severe symptom reported was ≥1 of: numbness/tingling, loss of taste or smell, vision loss, facial weakness/paralysis, seizure, weakness/paralysis of arms or legs, confusion, change in personality or behavior, or difficulty with urination or defecation. Data were extracted from the CANVAS-COVID database for analysis.

Results

Completed survey responses were received from 15,273 unvaccinated controls, 758,619 dose 1 recipients, 406,884 dose 2 recipients, and 126,586 dose 3 recipients. Rates of neurological events ranged from 15.9 (95 % CI 13.6–18.4) per 10,000 dose 1 ChAdOx1 recipients to 8.4 (6.5–10.8) and 7.9 (5.7–11.0) per 10,000 dose 3 mRNA-1273 and BNT162b2 recipients, respectively. Multivariable regression adjusted for age, sex, previous SARS-CoV-2 infection, and baseline health status showed an increased risk of neurological event among ChAdOx1 dose 1 recipients versus controls (adjusted OR 2.3, 95 % CI 1.2–4.3), but not among mRNA vaccine recipients after any dose. Risk of anaesthesia/paresthesia were increased following ChAdOx1 dose 1 (aOR 4.7, 1.7–13.1), and consistently but not statistically significantly higher following any dose of either mRNA vaccine. Risk of loss of smell/taste was decreased among recipients of any dose of either mRNA vaccine versus controls.

Conclusions

The results support the safety of COVID-19 vaccines while confirming reported associations between ChAdOx1 dose 1 and neurological events. Participant-based AEFI surveillance is a useful component of post-market surveillance programs.