This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax email@example.com with numerous contributions by others.
The Merck Manual and the Physician's Desk Reference give its
effectiveness as 95%. An article in a WHO publication (Hull and Ward)
estimates effectiveness at 80%. (As with other WHO estimates, the
lower effectiveness rating reflects an estimate of effectiveness in
the field in a variety of countries, including countries in the Third
World. Polio vaccine effectiveness can deteriorate if it is exposed to
too much heat, which can happen in vaccination programs in some