This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax firstname.lastname@example.org with numerous contributions by others.
Although the rotavirus vaccine has been withdrawn as of October, 1999,
I am retaining the answer to this question, in case it should be later
reintroduced in some form.
Efficacy persisted for two years in US and Finnish trials. Since
followup has only been done for two years, it is not known whether
efficacy persists beyond that time.