Seasonality of Guillain-Barré Syndrome During Vaccination Against Sars-Cov-2: A Country-Wide Analysis of Vaccines in Mexico

Introduction: Mass vaccination against SARS-CoV-2 was a critical step to curb COVID-19. However, hesitancy remains, partly due to actual or putative adverse events following immunization (AEFI). With 10 vaccines approved and seven widely used, Mexico has one of the broadest vaccine spectrums. Guillain-Barré syndrome (GBS) has been linked to some adenoviral vaccines; however, the seasonality of the disease during the vaccination period is unknown.Objective: To evaluate the seasonal variability of GBS cases reported through the national epidemiological surveillance system such as ESAVI during the vaccination season against SARS-CoV-2.Methods: We performed a retrospective, observational study of a national GBS registry among adults receiving SARS-CoV-2 vaccines in Mexico. The study period was from December 24, 2020, to December 31, 2022. All cases were mandatorily notified to the Health Ministry through an epidemiological surveillance system. Data was collected on a database using a standardized case report form.Results: During the study period, 139 cases were reported, 61 women and 78 men; in that period, 225,063,079 vaccine doses were administered, for an observed incidence of 0.62 cases per million doses. The median age was 46 (IQR 33–60) years. A seasonal peak was observed in spring (49.6% of the cases). Recipients of adenovirus vaccines were at greater risk of developing GBS than those receiving non-adenoviral vaccines, irrespective of seasonality. In the electrophysiological variants, the axonal patterns predominated.Conclusions: In our study, GBS occurring as AEFI was more frequent in the spring, a pattern that is compatible with sporadic, non-vaccine-associated GBS; with a predominance of axonal variants; the observed incidence is similar to the expected incidence of sporadic GBS. This should help mitigate vaccine hesitancy in a Country where still 21% of the population has not been immunized against SAR-CoV-2.