All the following are true about measles vaccine except –
**Core Concept**
Measles vaccine is a live attenuated vaccine that induces immunity against measles virus by stimulating the production of antibodies and activating cell-mediated immunity. The vaccine is typically administered in two doses, first at 9-12 months of age and a second dose at 16-18 years of age.
**Why the Correct Answer is Right**
Measles vaccine contains the Edmonston-Zagreb strain of the measles virus, which is a highly attenuated but still infectious strain. The vaccine is produced by growing the virus in chick embryo cell culture and then inactivating it with beta-propiolactone. The vaccine induces a strong immune response, with the production of IgG and IgM antibodies against the measles virus. The vaccine is also effective in preventing measles-related complications such as pneumonia and encephalitis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because measles vaccine does not contain a preservative such as thimerosal. The vaccine is produced in a preservative-free formulation to minimize the risk of adverse reactions.
**Option B:** This option is incorrect because measles vaccine does not require a booster dose in individuals who have previously received the vaccine. However, a second dose is recommended to ensure long-term immunity against measles.
**Option C:** This option is incorrect because measles vaccine does not contain a live attenuated strain of the mumps virus. The vaccine contains only the measles virus and does not provide immunity against mumps.
**Clinical Pearl / High-Yield Fact**
Measles vaccine is a safe and effective vaccine that has been widely used to prevent measles outbreaks. However, it is essential to note that the vaccine can cause a mild rash and fever in some individuals, which can be mistaken for the actual measles infection.
**Correct Answer:** D.