Abstract
Background and Aims:
The 13-valent pneumococcal conjugate vaccine (PCV13) is widely used to prevent invasive pneumococcal diseases in children. However, real-world safety data through active surveillance remain limited in many settings, including Eastern India. The aim of this study was to estimate the incidence, types, and risk factors of adverse events following immunization (AEFIs) with PCV13 among infants and young children in a tertiary care setting.

Methods:
A descriptive observational study was conducted at the Immunization Clinic of Calcutta National Medical College, Kolkata, from April to September 2024. Infants receiving any PCV13 dose were monitored for AEFIs using structured telephone follow-up at 24 hours, 48 hours, and 5–7 days post-vaccination. A standardized, pre-validated questionnaire was used for uniform data collection. Descriptive statistics, chi-square test, and reporting odds ratios were applied.

Results:
Out of 1,176 PCV13 doses given to 791 children, 569 AEFIs were reported in 435 children (48.38 per 100 doses). Fever (86.1%) was the most common reaction, followed by tenderness (16.87%), swelling (11.78%), and erythema (5.62%). Only one serious AEFI (0.09 per 100 doses) occurred. Younger age, preterm birth, and low birth weight were significant risk factors. AEFI incidence was highest after the first dose.

Conclusions:
PCV13 was generally safe and well tolerated. Most AEFIs were mild and self-limiting. The findings highlight the value of active surveillance and targeted caregiver education, especially for high-risk infants receiving their first dose.

Key words: Adverse Events, 13-Valent Pneumococcal Vaccination, India