Vaccine Component Reactions Explained

This solution analyzes potential adverse events linked to the active components of specific vaccines to determine which events are plausibly caused or precipitated by them.

Analysis of Vaccine Events

• 1. Anaphylaxis after measles vaccine: Anaphylaxis is a severe allergic reaction. While often triggered by trace substances, potent immune responses to vaccine antigens (the active component) can precipitate such reactions in susceptible individuals. This is a possible event.
• 2. Encephalopathy after DPT vaccine: The pertussis component of the DPT vaccine (especially older whole-cell formulations) has been historically associated with serious neurological events, including encephalopathy, although the exact causality and frequency are complex and debated. It is considered a potential risk linked to the active components.
• 3. Adenitis following BCG vaccine: Adenitis (swollen lymph nodes) is a common and expected local reaction to the live attenuated bacteria in the BCG vaccine. This reaction demonstrates the immune system responding to the active component. This is a plausible event.
• 4. Gastroenteritis following MMR vaccine: Gastroenteritis (inflammation of the stomach and intestines) is not typically considered a direct adverse effect caused by the active viral components (measles, mumps, rubella viruses) of the MMR vaccine. Such occurrences are usually coincidental rather than causally linked to the vaccine's active ingredients.

Conclusion on Vaccine Reactions

Based on the analysis, events 1, 2, and 3 are potentially caused or precipitated by the active components of the respective vaccines. Event 4 is unlikely to be directly caused by the active vaccine components.

Selecting the Correct Option

The correct combination representing events caused by active vaccine components is 1, 2, and 3.

Therefore, the correct option is 1, 2 and 3.