## Epidemiological Features of MMR ### Measles **Key Point:** Measles has an exceptionally high R₀ of 12–18, meaning one infected person infects 12–18 others in a susceptible population. It spreads via respiratory droplets and is highly contagious even before the rash appears. ### Mumps **High-Yield:** Mumps causes parotitis (swelling of salivary glands) but is NOT a highly fatal disease. The case fatality rate in developed countries is <0.1%, not >5%. While orchitis (testicular inflammation) occurs in 20–30% of post-pubertal males and can rarely lead to infertility, mumps is generally self-limited and non-fatal. ### Rubella **Key Point:** Rubella infection in the first trimester carries an 85–90% risk of congenital rubella syndrome (CRS), characterized by: - Cardiac defects (patent ductus arteriosus, pulmonary stenosis) - Ocular defects (cataracts, retinopathy, glaucoma) - Auditory defects (sensorineural hearing loss) - Intellectual disability ### MMR Vaccine **Clinical Pearl:** The MMR vaccine is a live attenuated vaccine that provides excellent protection (>95% after two doses) and confers lifelong immunity in the vast majority of recipients. | Feature | Measles | Mumps | Rubella | | --- | --- | --- | --- | | R₀ | 12–18 | 4–7 | 5–7 | | Primary manifestation | Rash, fever, cough | Parotitis | Rash, arthralgia | | CFR (developed countries) | 0.1–0.2% | <0.1% | <0.1% | | CRS risk (1st trimester) | — | — | 85–90% | | Vaccine efficacy (2 doses) | >95% | >95% | >95% | **Warning:** The distractor claims mumps CFR >5%, which is grossly inflated and incorrect.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.