There are two types of polio
immunizations available in the United States. Both of these vaccines
take advantage of the fact that infection with polio leads to an
immune reaction, which will give the person permanent, lifelong
immunity from re-infection with the form of poliovirus for which the
person was vaccinated.
The Sabin vaccine (also called the
oral polio vaccine or OPV) is given to infants by mouth at the same
intervals as the DPT (three doses). It contains the live, but
weakened, poliovirus, which make the recipient immune to future
infections with poliovirus. Because OPV uses live virus, it has the
potential to cause infection in individuals with weak immune
defenses (both in the person who receives the vaccine and in close
contacts). This is a rare complication, however, occurring in only
one in 6.8 million doses administered and one in every 6.4 million
doses from having close contact with someone who received the
vaccine.
The Salk vaccine (also called the
killed polio vaccine or inactivated polio vaccine) consists of a
series of three shots that are given just under the skin. This
immunization contains no live virus, just the components of the
virus that provoke the recipient's immune system to react as if the
recipient were actually infected with the poliovirus. The recipient
thus becomes immune to infection with the poliovirus in the future.
In the 13 years following the
launching of the Global Polio Eradication Initiative, the number of
cases has fallen 99% from an estimated 350,000 cases to less than
3,500 cases worldwide in 2000. At the end of 2000, the number of
polio-infected countries was approximately 20, down from 125. The
goal of the World Health Organization (WHO) is to have polio
eliminated from the planet by the year 2005. The virus has still
been identified in Africa and parts of Asia, so travelers to those
areas may want to check with their physicians concerning booster
vaccinations.
