According to the National Immunisation Schedule (NIS) of India, which vaccine is the most common cause of adverse events reported in the immediate post-immunisation period in infants?

Explanation

## Most Common Adverse Event in NIS **Key Point:** The DPT (Diphtheria, Pertussis, Tetanus) vaccine, particularly the whole-cell pertussis component, is the most commonly reported vaccine causing adverse events in the immediate post-immunisation period in Indian infants. ### Adverse Events Profile by Vaccine | Vaccine | Common Adverse Events | Timing | Severity | |---------|----------------------|--------|----------| | DPT (whole-cell) | Fever, local swelling, crying, drowsiness, convulsions | 0–48 hours | Mild to moderate; rare severe | | OPV | Vaccine-derived poliovirus (VDPV) in immunocompromised, mild GI upset | Days 4–30 | Usually mild | | Hepatitis B | Local pain, mild fever | 0–24 hours | Mild | | BCG | Local ulceration, regional lymphadenitis (BCG-itis) | Weeks 2–12 | Usually self-limiting | **High-Yield:** DPT vaccine accounts for the majority of reported adverse events in the NIS because: 1. It is administered to all infants (universal coverage) 2. The whole-cell pertussis component is more reactogenic than acellular formulations 3. Fever and local reactions occur in 10–50% of vaccinees 4. Convulsions (febrile or afebrile) are rare but notable ### Clinical Pearl While serious adverse events (encephalopathy, anaphylaxis) are rare, the DPT vaccine's reactogenicity is well-documented. Most adverse events are self-limiting and managed with supportive care (antipyretics, reassurance). The benefits of DPT vaccination far outweigh the risks of the diseases it prevents (diphtheria, pertussis, tetanus). **Warning:** Do not confuse "most common adverse event" with "most serious adverse event." Serious events like anaphylaxis are rare across all vaccines; DPT's frequency of mild-to-moderate events makes it the most commonly reported. [cite:Park 26e Ch 6]