Measles is a common viral infection. Babies gain passive immunity to measles. 

a Explain:

i. The term passive immunity

ii. How babies gain passive immunity.

A vaccine for measles has been available since the 1960s. Global vaccination programmes include providing vaccination for measles, but it is important that the vaccine is not given to babies too early.

b. Explain why:

i. The vaccine for measles should not be given too early [3]

ii. Measles has not been eradicated, even though a vaccine has existed since the 1960s.

c. Smallpox was an infectious disease that was finally eradicated in the late 1970s. Explain how vaccination was used in the eradication of smallpox.