BI-1450
Vaccines
Biology · Secondary 4 · Hard · Vaccines
A graph shows the number of measles cases in a country from 1950 to 1970. A measles vaccine was introduced in 1958. After 1958, the number of cases drops sharply but small outbreaks still occur. Which conclusion about the vaccine is best supported by this pattern?
- The vaccine greatly reduced measles cases but did not eliminate the disease
- The vaccine had no effect because some cases still occurred
- The vaccine completely prevented measles in all vaccinated people
- The vaccine increased measles cases by weakening immunity
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