A five-year prospective cohort study has just been completed. the study was designed to assess the association between supplemental vitamin a exposure and mortality and morbidity for measles. the rr for incidence of measles was 0.75 and the rr for measles mortality was 0.5. Assume these RR are significant. Regarding the RR reported above, which statement is correct? a. Exposure to vitamin A appears to protect against morbidity and mortality for measles.
b. Exposure to vitamin A appears to be a risk factor for morbidity and mortality for measles.
c. Exposure to vitamin A is not associated with morbidity and mortality for measles.
d. Exposure to vitamin A is a risk factor for morbidity and a protective factor for mortality for measles.