Effects of Prior Vaccination on the Reduction of Cognitive Deficits Associated with COVID-19 Infection: A Mini-Review

Introduction: COVID-19 infection has been frequently associated with cognitive deficits that persist for months after infection, but the impact of vaccination on preventing these deficits remains uncertain. Evidence suggests that immunization reduces the incidence and severity of post-COVID symptoms overall, however, few studies have evaluated the influence of vaccination on cognition through objective measures. Methods: A systematic review was conducted following PRISMA guidelines and registered in PROSPERO (ID CRD42025636772). The search was performed in the PubMed/MEDLINE and Scopus databases. Studies that analyzed cognition as output through objective measures and compared vaccinated and unvaccinated individuals at the time of infection were included. Results: A total of 1796 records were identified, of which only five fully met the inclusion criteria. The included articles varied significantly in terms of the instrument used, study design, and sample size. Four out of the five studies found no associations between prior vaccination and cognitive deficits. However, the only study that identified a subtle difference among individuals with at least two doses of the vaccine had a substantially larger sample than all the others combined. Methodological inconsistencies in cognition assessment, variability in definitions regarding vaccination status, and the absence of deficit stratification by specific cognitive domains limit the interpretation of the findings. Conclusion: Although vaccination may play a role in protecting against cognitive deficits following COVID-19 infection, the evidence remains limited and inconclusive. Further studies with greater standardization in defining vaccination status, along with the use of comprehensive objective assessments, are needed for a better understanding of this relationship.