Poliomyelitis (shortened to polio) has been around for thousands of
years, and there is still no cure, but at the peak of its devastation in the United
States, Dr. Jonas Salk introduced a way to prevent it. Polio attacks the nerve
cells and sometimes the central nervous system, causing muscle wasting,
paralysis, and even death. The disease, whose symptoms are flu like, stuck
mostly children, and in the first half of the 20th century the epidemics of polio
were becoming more devastating. Salk, while working at the Virus Research
Lab at the University of Pittsburgh, developed a polio vaccine, and the
medical trials to prove its effectiveness and safety are still being analyzed.
Fifty years ago the largest medical experiment in history took place to
test Salks poliomyelitis vaccine. Close to two million children across the
United States and Canada were involved in the trial, which was administered
by the National Foundation for Infantile Paralysis (NFIP), also known as the
March of Dimes. The foundation, created in 1938 by President Franklin D.
Roosevelt (a polio victim) and his law partner Basil OConnor. Across the
United States, 623,972 school children were injected with the vaccine or a
placebo, using a double blind technique in which neither recipient nor
administrator knew which one there were getting. The results, announced in
1955, showed good statistical evidence that Jonas Salks killed virus
preparation was 80-90% effective in preventing paralytic poliomyelitis.
The statistical design used in the experiment was singular, prompting
criticism. Eighty four test areas in eleven states used a textbook model: in a
randomized, blinded design all participating children in the first three grades
of school (ages 6-9) received injections of either vaccine for placebo and
were observed. At the same time though, 127 test areas in 33 states used an
observed control design: where the participating children in the second
grade received injections of vaccine, no placebo was given, and children in all
three grades were then observed for the duration of the polio season. The use
of the dual protocol illustrates both the power and the limitations of
randomized clinical trials. The control trials with the placebo were important
to define the vaccine as the product of scientific medicine, while the observed
trials were done to maintain public support for the vaccine.
In 1953, Salk presented his tests of a polio vaccine to the Immunization
Committee, the scientific advisory committee for the NFIP. The test results
seemed promising to Basil OConnor, as the children had shown no ill effects
and the levels of polio antibodies in their blood had risen. However, several
of the senior virologist on the committee questioned the relation of antibodies
to permanent immunity. Despite the virologists critique, OConnor believed
that his organization owed it to the volunteers and donors to proceed and
called for the planning of a major field study.
OConnor, in November of 1953, announced that the field trials would
begin in the spring and the observed plan would be used. Within a month,
health departments in 38 states had responded, enthusiastic about the
prospect of a vaccine. A few state officials however, questioned the
impartiality of the evaluation run by the foundation, and not by scientists.
Responding to the criticism OConnor called an meeting of an advisory
group to review the statistical design. When the group convened, it had
decided to go strictly with the placebo controlled studies.
This change lessened slightly the criticism of the field trials, and the
National Foundation for Infantile Paralysis tried to reconcile it scientific and
political problems by working through state health departments. The critics
still denounced the trials as flawed, and the debates of the scientific validity
of the experiment continue to this day.Words
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