LIVE POLIO IRUS VACCINES

114
Safety-Field Evidence of Safety
the number of participating families had been
reduced to 42.
TABLE 1. AGE OF STUDY POPULATION: 48
FAMILIES IN WHICH TRIVALENT VACCINE WAS
GIVEN TO ONE CHILD IN EACH FAMILY
TOTAL
NUMBER AGE NUMBER
NUMBER
VACCINEES 48 6-12 MOS 27
13-18 , 19
19-22 , 2
CONTACTS 77 2-12 MOS. 6
13-23 .Y 6
2-'4 YEARS 65
Vaccine dosage. Trivalent vaccine, kindly supplied
by Dr. H. Cox, was used. The titer for
each of the three types was approximately 105
to 1055 ' TCD 50 , and this amount was contained in
2 ml. of cherry flavored syrup. The placebo
given to contacts consisted of cherry syrup only.
A second similar dose of the same lot of vaccine
was administered to the index children one
month after the first dose.
Collection of specimens. Pre-vaccinal rectal
swabs and blood specimens were obtained from
the index children and their contacts. Following
vaccine (or placebo) administration, rectal swabs
were collected twice weekly from the entire study
group. A second blood collection was made one
month after the first dose of vaccine and immediately
before the second dose. Rectal swab collections
continued for another two weeks, and
final, third blood specimens were obtained after
one month from the index children but not from
the contacts.
Laboratory tests. Virus isolation was carried
out in monkey kidney (MK) tissue cultures. All
rectal swabs were tested in MK bottle cultures,
and in addition, the pre-vaccinal specimens were
tested in Hep.-2 cells. Identification of isolates
was carried out in MK tube cultures, using appropriate
antisera, singly or in combination, as
indicated.
Neutralization tests on the blood specimens of
vaccinees were performed by the CPE (cytopathogenic
effect) method in tubes; on sera from
contacts, the colorimetric method in plastic
panels was used, but some specimens were tested
by both methods.
RESULTS
In the course of the study, 1703 rectal swabs
were examined, 691 from the index children, and
1012 from their contacts (Table 2). A total of
892 virus strains was isolated, 637 of them being
polioviruses. Surprisingly few of the vaccinees
were found to be excreting mixtures of different
types of polioviruses: only 45 specimens contained
more than one type, and in only three
were all three types present.
TABLE 2.
ISOLATION OF VIRUSES FROM RECTAL SWABS, INDEX CHILDREN AND CONTACTS
NUMBER
NUMBER RECTAL SWABS NO. STRAINS ISOLATED
OF
CHILDREN NO. TESTED POSITIVE POLIOVIRUSES OTHERS
VACCINEES 48 691 427 (62%) 378 98
CONTACTS 77 1012 408 (41 %) 259 157
TOTAL 125 1703 835 (49%) 637 255
892