Live vaccines are -a) TTb) BCGc) DPTd) OPVe) MMR
**Core Concept**
Live vaccines are composed of weakened or attenuated forms of a pathogen, which stimulate a mild immune response and provide long-lasting immunity. This type of vaccine is particularly effective against certain infectious diseases, such as tuberculosis and measles.
**Why the Correct Answer is Right**
The correct answer options are live vaccines that are commonly used in pediatric and adult vaccinations. **BCG (Bacillus Calmette-Guérin)** is a live attenuated vaccine used against tuberculosis, while **MMR (Measles, Mumps, and Rubella)** is a combination vaccine that contains live attenuated strains of the measles, mumps, and rubella viruses. These vaccines are effective because they stimulate a strong immune response without causing the full-blown disease.
**Why Each Wrong Option is Incorrect**
* **Option A:** TT (Tetanus Toxoid) is a killed vaccine, not a live vaccine. It contains inactivated tetanus toxin that stimulates an immune response.
* **Option C:** DPT (Diphtheria, Pertussis, and Tetanus) is a combination vaccine that may contain either killed or live pertussis components, but it is not a live vaccine as a whole.
* **Option D:** OPV (Oral Poliovirus Vaccine) is a live attenuated vaccine, but it is not among the options listed in the question.
**Clinical Pearl / High-Yield Fact**
Live vaccines should be handled with care and stored in a way that prevents them from coming into contact with other vaccines or substances that may inactivate them.
**Correct Answer:** B. BCG.