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Although the rotavirus vaccine has been withdrawn as of October, 1999,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.
The rotavirus vaccine doesn't confer full immunity, but protects
against severe illness (this is also the case with natural immunity
from prior rotavirus infections). Trials by the manufacturer, used for
FDA approval, showed the following results:
Trial 1: None of the infants receiving the vaccine got dehydrated,
compared to 3% in the placebo group. 11% fewer in vaccine group needed
a visit to the doctor. 88% showed elevated IgA titers.
Trial 2: 9% of infants in placebo group saw a doctor for diarrhea and
vomiting, compared with 2% in vaccine group. None in the vaccine group
Both trials were by the manufacturer, and not published in the medical
literature at the time of approval.
A third trial, in Finland, showed similar results.