a) Administration of the second dose of measles-containing vaccine should be administered only at 4 to 6 years of age.
b) Between 2% and 5% of people do not develop measles immunity after the first dose of MMR.
c) In 1954, Enders and Peebles isolated a measles virus from the blood of a 13-year-old boy named David Edmonston during a measles outbreak in Boston, and the isolate was transformed into the vaccine strain.
d) Some people have a memory of measles vaccination but no longer have written documentation, and this can be accepted as evidence of measles immunity.
Answer: b and c are true