Post exposure vaccination for measles should be done in: September 2009
**Core Concept**
Measles post-exposure vaccination is a strategy to prevent measles infection in individuals who have been exposed to the virus. The timing of post-exposure vaccination is critical to ensure its effectiveness.
**Why the Correct Answer is Right**
Post-exposure vaccination for measles is recommended 72 hours after exposure. This allows time for the immune system to respond to the vaccine and prevent the development of measles infection. The measles vaccine is a live, attenuated vaccine that works by stimulating the body's immune system to produce antibodies against the measles virus.
**Why Each Wrong Option is Incorrect**
**Option A:** Vaccination within 48 hours of exposure may not be effective as the immune system may not have time to respond to the vaccine. This can lead to breakthrough infections.
**Option B:** Vaccination more than 10 days after exposure is generally ineffective as the individual may have already developed immunity to the measles virus.
**Option C:** Immediate vaccination upon exposure is not recommended as it may not allow sufficient time for the immune system to respond to the vaccine.
**Clinical Pearl / High-Yield Fact**
Measles post-exposure vaccination is most effective when administered 72 hours after exposure, and a second dose is recommended for individuals who are not immune to measles.
**Correct Answer: C. Immediately upon exposure is not recommended.**