Prospective Safety Cohort Study After VLA1553 Vaccination in Municipalities Selected for Participation in the VLA1553 Pilot Vaccination Strategy in Brazil

This is an observational study with primary data collection, which will combine a prospective safety cohort study and an SCRI study.

Inclusion Criteria: 1. Male or female participants who received a single dose of VLA1553 at a vaccination unit while participating in the pilot vaccination strategy. 2. Individuals that are target for the pilot vaccination strategy at the time of vaccination. 3. Individuals understanding and being able to comply with all scheduled follow-up calls/contacts and study procedures. 4. Have given informed consent/assent prior to entering the study. Exclusion Criteria: 1. Individuals who have received investigational products within the 30 days prior to VLA1553 vaccination, or individuals who have received VLA1553/IXCHIQ previously or any authorized or approved CHIKV vaccine. 2. Individuals who are not expected to remain available for the study follow-up for the next 24 weeks after vaccination. 3. Pregnant women: women exposed to VLA1553 anytime during their pregnancy or within 30 days preceding their last menstrual period will be invited to participate in a separate pregnancy surveillance study (study identifier VLA1553-403).