Parental perceptions of adverse events associated with the whole-cell pertussis vaccine in Brazil

To better understand parents/caregivers' perceptions of adverse events (AEs) associated with the whole-cell pertussis vaccine and the impact of family routine activities. This cross-sectional study was conducted in the city of São Paulo, Brazil, using a parent-reported outcomes approach to describe the perception of AEs following immunization with the whole-cell pertussis vaccine. A total of 1260 parents/caregivers of children who received a whole-cell pentavalent vaccine were enrolled in the study. The most frequently reported AE was tenderness/pain at the injection site (72.4%). Parents/caregivers also reported at least some grade (a little bit more, moderate, or significant/severe) of redness at the injection site (25.2%), swelling (32.4%), a fever ≥38 °C (41.9%), vomiting (7%), and changes in appetite (27.1%), sleeping (34%), and crying (43.7%) patterns. Overall, 86.8% of the parents/caregivers reported at least one AE or change in the child's behavior. A significant positive gradient was observed, i.e., the higher the income, the higher the frequency of AEs/behavior change perceived by the parents/caregivers. The analysis by dose did not show significant differences, except for local pain/tenderness (77.6% vs. 73.5% for D1 and 65.4% for D3, p = 0.001) and changes in child's appetite (34.3% vs. 22.9% for D1 and 26% for D3, p = 0.001) that were more frequent among children receiving the first booster, while changes in child's sleeping (39.1% vs. 26% for D3 and 34.3% for the first booster, p < 0.001) and crying (49% vs. 37.7% for D3 and 42.2% for the first booster, p = 0.003) patterns were more frequent among those receiving D1. Our study showed that the reported AEs following wP-pentavalent vaccine significantly impact Brazilian children and their families. The switch to less reactogenic vaccines, such as aP hexavalent vaccine, can diminish this impact and contribute to recovering high VCR rates, avoiding outbreaks of vaccine-preventable diseases (VPDs). • High Prevalence of Adverse Events (AEs): with the whole cell vaccine Over 86% of reported AE or behavioral change in children. • Most Common reported AEs: Pain/tenderness, fever ≥38°C and changes in crying and sleeping patterns were most frequently. • A significant positive association was found between household income and the frequency of perceived AEs • Parental lifestyle disruptions were the strongest predictor of satisfaction, with a positive gradient • The findings support transitioning to to less reactogenic vaccines (acellular pertussis vaccine (e.g. hexavalent vaccine).