We evaluated the efficacy of a hepatitis care coordination intervention to improve linkage to hepatitis A virus (HAV) and hepatitis B virus (HBV) vaccination and clinical evaluation of hepatitis C virus (HCV) infection among methadone maintenance patients. Methods. We conducted a randomized controlled trial of 489 participants from methadone maintenance treatment programs in San Francisco, California, and New York City from February 2008 through June 2011. We randomized participants to a control arm (n = 245) and an intervention arm (n = 244), which included on-site screening, motivational-enhanced education and counseling, on-site vaccination, and case management services. Of the 150 participants in the intervention group who needed the combined HAV--- HBV vaccine, 115 received the vaccine within 30 days of the vaccine being recommended. Of the 150 participants in the control group who needed the combined HAV-HBV vaccine,18 received the vaccine within 30 days of the vaccine being recommended.

- Interpret the risk difference estimate from question25in a sentence.

a. The absolute difference in proportions (probabiity) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is 0.65.

b. The absolute difference in proportions (probability) of getting vaccinated within 30 days for subjects in the intervention group compared to subjects in the control group is -0.65.

c. An individual who receives the intervention has 65 times the risk (probability) of being vaccinated within 30 days compared to if this individual was in the control group.

d. An individual who receives the intervention has a 65% lower risk (probability) of being vaccinated within 30 days compared to if this individual was in the control group.

e. An individual who receives the intervention has a 65% greater odds of being vaccinated within 30 days compared to if this individual was in the control group.

f. An individual who receives the intervention has a 65% lower odds of being vaccinated within 30 days compared to if this individual was in the control group.