Pain Response and Associated Factors During Bacillus Calmette-Guérin Vaccination in Newborns: A Cross-Sectional Study

Bacillus Calmette-Guérin (BCG) vaccination is routinely administered shortly after birth in many countries, including Vietnam. Although brief, this procedure may induce substantial pain during a critical period of neonatal neurodevelopment. Evidence on pain responses during BCG vaccination and modifiable procedural factors remains limited. This study aimed to assess neonatal pain during BCG vaccination and identify factors associated with severe pain.

We conducted a cross-sectional observational study involving 172 newborns aged less than 48 hours who received intradermal BCG vaccination at a tertiary hospital in Ho Chi Minh City, Vietnam. Pain was assessed immediately before vaccination and immediately after needle withdrawal using the Neonatal Infant Pain Scale (NIPS). Severe pain was defined as a NIPS score of 5 or higher. Infant characteristics and procedural variables, including sex, mode of delivery, infant feeding prior to vaccination, and vaccination order (BCG first vs. BCG injected after hepatitis B vaccination), were recorded. Associations with severe pain were examined using Poisson regression with robust variance.

The mean NIPS score after BCG vaccination was 3.83 ± 1.72. Overall, 64/172 newborns (37.2%) experienced severe pain (NIPS score ≥ 5). Feeding before vaccination was associated with a lower prevalence of severe pain (aPR = 0.35; 95% CI: 0.19-0.65), whereas receiving BCG after hepatitis B vaccination (aPR = 1.87; 95% CI: 1.27-2.77) and assisted delivery (aPR = 1.93; 95% CI: 1.01-3.66) were associated with a higher prevalence of severe pain.

Procedural pain during BCG vaccination was common among newborns. Feeding before vaccination, vaccination order, and assisted delivery were associated with neonatal pain response and may represent clinically relevant procedural factors. Given the single-center observational design, these findings should be interpreted cautiously and require confirmation in a controlled intervention. Simple, feasible pain-reduction strategies should be considered during routine neonatal vaccination.