Safety and effectiveness of the booster dose of mRNA COVID-19 vaccines in people with multiple sclerosis: A monocentric experience.

The administration of the booster dose in pwMS showed an overall good safety profile and protected 79% of the patients from SARS-CoV-2 infection. The observed association between the risk of infection after the booster dose and both younger age at vaccination and shorter interval period to the booster dose suggest that unobserved confounders, possibly including behavioural and social factors, play a relevant role in determining the individual propensity to get infected with COVID-19.