LIVE POLIO IRUS VACCINES

Large-Scale Field Trial with Oral Cox-Lederle Vaccine in Dade County 439
immunization, as well as other medical and
social items. More reliable data than previously
have been available concerning the immune
status to poliomyelitis of a large metropolitan
area will also be provided. The uncorrected
interview survey data (Table 4) suggest that the
percentage of the population that has received
three or more injections of the Salk-type vaccine
is about 83 per cent of the five-19-year-old-age
group, 45 to 55 per cent in the 0-4 and 20-39-
year-age group, and less than 20 per cent in the
40-and-over-age group. The serologic results required
to complete Table 5 are not yet available.
Related Research. In addition to the actual
field trial, we have undertaken or are cooperating
in a series of related projects. These include
the following:
1. A study of polioviruses and other enteroviruses
from sewage samples collected from
representative points at weekly intervals before,
during, and after the oral immunization program.
2. An enterovirus surveillance program by
Dr. A. Gelfand of the U. S. Public Health Service,
based on rectal swabs submitted monthly
from 100 Dade County infants and children.
3. Studies by Dr. R. Murray and associates
at the National Institutes of Health on polioviruses
excreted by humans during the field
trial and of vaccine potency.
4. A prospective and retrospective multidisciplinary
evaluation of the health education
and other social factors, which contributed to
the high degree of community acceptance and
participation.
ANTIBODY RESPONSE AND
EFFECTIVENESS
Although the final proof of the effectiveness
of this and other polio vaccines depends on
careful and prolonged epidemiologic surveillance
for paralytic disease, it can be reasonably assumed
that field effectiveness will parallel the
antibody response to the vaccine.
In order to determine the antigenic potency
of the vaccine used, blood specimens were collected
immediately prior to, and three to four
weeks after, oral vaccination from approximately
2,300 elementary school students and 850 infants
and young adults. The elementary school students,
aged six to 12 years, were volunteers,
consisting of approximately 50 per cent of the
student body of six representative elementary
schools and a rather highly Salk-immunized
group. The infants and young adults included
university students, military personnel and their
dependents, and Health Department clinic clientele,
most of whom had received no prior Salktype
polio vaccine.
The poliovirus neutralizing antibody levels are
being determined on paired sera in one of three
laboratories: Variety Children's Research Foundation,
directed by Dr. M. M. Sigel, Professor
of Microbiology, University of Miami School of
Medicine; Florida State Board of Health Laboratory,
directed by Dr. N. J. Schneider; and by
Microbiological Associates, Bethesda, a commercial
laboratory with vast experience in this
field. Microbiological Associates is using the
metabolic inhibition (pH) test; the other laboratories
are using the cytopathogenic effect (CPE)
test. Specimens tested by the pH method which
show absent or low titers by this technique
and approximately 5 per cent of all other paired
specimens, are being re-tested by one or more
of the other laboratories by the different technique.
All specimens are effectively coded, but
by a system of unit packaging it is insured that
all specimens from a given individual will be run
simultaneously. Since this is not primarily a
paper on laboratory technique and since the
complete laboratory data are not yet available,
the results here reported are those obtained from
one laboratory using the pH test.
As of this date, we have received the reports
on the results of tests from approximately 2,500
individuals. In this group there were 594 individuals
who lacked measurable poliovirus
neutralizing antibodies to one or more of the
three types of poliovirus. The numbers of individuals,
both by total and by broad age group,
in each of the seven possible combinations of
antibody gap to one or more types of poliovirus,
are shown in Table 6. In this highly biased sample,
the majority, 61 per cent, were in the age
group of five through 14 years. Table 7 gives
the Salk status of these 594 individuals. It will
be noted that relatively few individuals lacking
Type 2 antibodies had received three or more