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As recently as the 1950's, polio was a fairly common disease,
much feared by parents of small children. With the development of the first inactivated
polio vaccine, in 1954 which was given by injection, this picture began to change. Over
the next several years, as this vaccine gained acceptance and as the newer oral vaccine
(first licensed in 1961) came into use, the number of cases of paralytic polio plummeted,
from more than 20,000 in 1952 until today when only a few cases occur each year in the
United States.
Poliomyelitis is a contagious viral disease that, in its
severe form, can cause permanent paralysis, and occasionally death. Polio is an extremely
dangerous disease, and every parent should know about it.
Polio is caused by a virus that lives in the nose, throat
and, especially, in the intestinal tract of a person infected with it.
Many people who are infected by the polio virus have no
symptoms but may still spread the infection to others.
The milder forms of polio usually begin abruptly and last, at
most, a few days. When symptoms are present, they include fever, sore throat, nausea,
headache, and stomach ache. Sometimes, the patient will feel pain and stiffness in the
neck, back, and legs.
Paralytic polio begins with these same symptoms, but severe
muscle pain is usually present, and if paralysis occurs, it does so within the first week.
There is no specific treatment for polio, and the degree of recovery varies from patient
to patient. About half of all patients who recover have mild disabilities or none at all.
The rest may suffer permanent paralysis.
Our success in preventing the spread of wild polio virus has
been so great that most of the recent cases have resulted from the rare side effects of
oral polio vaccine. Because of this fact, some people have asked why we should continue to
use oral polio vaccine. The reason is that, even though we may not have much wild polio
virus spreading here now, there are thousands of cases in the rest of the world;
therefore, there is a risk of polio being reestablished here if our children are not
immunized. Oral polio vaccine is thought to establish a more effective community barrier
to polio infection than inactivated polio vaccines.
Polio Immunization
Immunizations with "live" oral polio vaccine (OPV)
is one of the best ways to prevent polio. It is given by mouth starting in early infancy.
Several doses are needed to provide good protection. Young children should get two or more
doses in the first year of life and another dose at 15 months of age. An additional dose
is important for children when they enter school or when there is a high risk of polio,
such as during an epidemic or when travelling to a place where polio is common.
The vaccine is easy to take and is effective in preventing
the spread of polio. A primary series of OPV gives protection in over 90 percent of those
who receive the vaccine, probably for life. Because OPV viruses live for a time in the
intestinal tract of the person who is immunized, some of the viruses pass in the stool and
can spread from the immunized person to those in close contact (usually household
members). This may help to immunize these persons and is one of the advantages of
OPV.
Besides the "live" oral polio vaccine (OPV), there
is also an inactivated (killed) polio vaccine (IPV) given by injection which protects
against polio after several shots. Because OPV seems to provide stronger immunity in the
intestinal tract (where infection first occurs), is simpler to administer, and is more
effective in preventing the spread of polio virus than IPV; most polio experts feel that
the oral vaccine is more effective for controlling polio in the United States.
Both the Immunization Practices Advisory Committee of the
Public Health Service an the American Academy of Pediatrics recommend oral polio vaccine
as the preferred polio vaccine for people up to the 18th birthday.
Inactivated polio vaccine is recommended for persons needing
polio immunization who have low resistance to serious infections or who live with persons
with low resistance to serious infections. It may also be recommended for previously
unimmunized adults who plan to travel to a place where polio is common or for previously
unimmunized adults whose children are to be immunized with OPV. It is not widely used in
this country at the present time, but it is available.
Possible Side Effects and Adverse
Reactions to Polio Immunization
Very rarely (about 1 in every 7.8 million doses distributed),
oral polio vaccine (OPV) causes paralytic polio in the person who is immunized. The risk
is higher following receipt of the first dose of OPV and in persons with abnormally low
resistance to infection and may be higher in adults being immunized. Also, on rare
occasions (about 1 in every 5.5 million doses of OPV distributed), paralytic polio may
develop in a close contact of a person recently immunized with OPV. This risk also is
somewhat higher to contacts of persons receiving their first dose of OPV. These risks are
very low, but they should be recognized and balanced against the risk of disease.
Inactivated polio vaccine (IPV) is not known to produce any side effects other than minor
local pain and redness.
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