In an August 2013 article published in American Journal of Public Health, researchers report the results of a two-site (San Francisco and NYC) randomized trial: here is a description of the trial and itsstudy sample from the article abstract:

Objectives. 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.

- Suppose you were to misinterpret the odds ratio as the relative risk. (i.e. report the value of the estimated odds ratio, but mislabel it as a relative risk estimate) What would this do to the reported efficacy of the intervention program with regard to the vaccination outcome (underestimate or over-estimate the efficacy)?-

a. Under estimate the reported efficacy in terms of individual risk of getting the vaccine

b. Over estimate the reported efficacy in terms of individual risk of getting the vaccine

c. This would have little to no impact