LIVE POLIO IRUS VACCINES

342
Efficacy-Laboratory Evidence
342 EfiayLbraoyEiec
behavior in the human body. In particular, it
was thought that efforts to demonstrate the fed
viruses in the blood and the pharynx would not
be too burdensome to the participating population.
Accordingly, procedures designed to implement
these efforts were built into the over-all
plan of the experiment. These special efforts
were limited to children in this study but were
tried elsewhere in a group of adults in a study
which will be reported.?
1. A Comparison of Monovalent and Trivalent Vaccines
MATERIALS AND METHODS
The attenuated strains of poliovirus used in
this study were derived from the same seed that
was used to produce the vaccine for the 1958
Como Village study that was reported in 1959.
They were also essentially the same strains that
were used by Martins da Silva et al. in an earlier
study which included only newborns and infants
under six months of age. 4 From the same seed
also came the strains that were and are continuing
to be used in the various large scale vaccination
operations in South and Central America.Y 6
However, the dosage form and the dose were
different. The vaccine used in the 1958 Como
Village study was adsorbed on granular gelatin
and dispensed in hard gelatin capsules. The
virus dosage for this preparation was 4.8 logs for
Type 1, 5.1 logs for Type 2, and 5.3 logs for Type
3. For the present study, the vaccine viruses
were suspended in a liquid, sweetened and
pleasantly flavored with cherry. The dose for
each virus type was 6.1 logs whether used as a
monovalent vaccine or a trivalent vaccine. The
drinking dose for both the monovalent and the
trivalent types was 2 cc. The liquid dosage form
has the obvious advantages of such preparations
especially for children. In addition, the stabilizer
used has been found to insure a good "shelf life".
And finally, it is easier, in a liquid preparation,
to regulate the repeatability of the same virus
quantity from dose to dose. 7
Population Characteristics and Location. The
population chosen for this study consisted of
married University of Minnesota students and
their children, living in Grove East, a housing
village maintained by the University for student
use. The village was in the city of St. Paul.
There were residential areas on two sides and on
the other two there were the grounds of the St.
Paul Campus of the University of Minnesota.
The dwelling units were duplex back-to-back
structures of the metal barracks type. The water
supply and sewage facilities were those of the city
itself. This area, which was not quite as congested
as the Como Village area of the 1958 study 1 also
offered much less communal activity. There
was no cooperative store; there was no local
student's union; and the meager meeting place
was so inadequate as to be generally shunned.
Although there was some visiting and exchange
of baby sitters, families, in general, tended to
keep to themselves. It was difficult to set up a
community meeting of any kind.
The characteristics of the volunteering population
with respect to age and vaccinal status
with Salk vaccine are shown in Table 1. The
mean age of the fathers was 27, and the mean age
of the mothers, 26. This is comparable to the
adult group in the Como Village study. The
children in this study were a little older with a
mean age of 3.3 years. This is almost a year
older than the Como Village children, on the
average. Coverage with Salk vaccine was better
over-all than it had been in Como Village, and
in addition, fourth doses now appeared. Twothirds
of the children, 41.5 per cent of the fathers.
and 69 per cent of the mothers had received three
or more doses of Salk vaccine. Only a bare
10 per cent had received no Salk vaccine at all.
The total of 219 participants represented a little
more than 40 per cent of the village's population.
Design. The operating plan for the study is
displayed in Table 2. It is obvious that there
are two groups of participants; one destined to
receive monovalent vaccine sequentially in the
order of Types 2, 1, and 3, and the other to receive
a trivalent vaccine preceded by two doses
of placebo. The members of these two groups
were chosen in a purely random manner. The
scheduling of the blood and stool samples in
relation to the feedings can be appreciated by
consulting the table. Throat swabs for pharyngeal
virus recovery and capillary blood for