LIVE POLIO IRUS VACCINES

Studies on Live Poliovirus Vaccine in Japan
197
and of those, nine were single negative and two
triple positive. Three of them became infected
one week after the vaccine trial started. In
another experiment, 18 infants were divided into
two groups of nine each, one being one to four
months old and the other six to 18 months old.
Three of each group were fed with the Cox
monovalent vaccine and the remaining six served
as contacts. Virus isolation was undertaken from
the stools in order to follow up the spread of
virus to contacts. The contact babies who were
older than six months were easily infected with
poliovirus, while those younger than four months,
who could not move by themselves, did not become
infected as easily within four weeks as the
older babies (Table 8). The maternal antibody
was found not to be capable of inhibiting multiplication
of such an attenuated virus in the intestines.
The stimulation of antibody formation
for Type 2 poliovirus was seen in the contact
group after Type 1 vaccine was fed to the vaccine
group and viceversa. All of them except
two showed positive immune response after feeding.
However, the immune response for Type
3 poliovirus was poor in the vaccine group after
feeding of any type of vaccine.
Fifteen strains of Type 1, two strains of Type
2, and 26 strains of Type 3 poliovirus were isolated
from the stools. They were isolated sooner
or later within three weeks and sometimes persisted
for eight weeks in the contact group after the
vaccine was fed. The type of poliovirus recovered
from the contact group was related to the
immune status in a manner similar to that of the
vaccine group.
As for the genetic stability of poliovirus excreted
by the vaccinees and the contacts, 20 new
isolates of Type 1 poliovirus did not show any
change in MS marker. On the other hand, out
of 24 strains of Type 3 poliovirus, three were
found to change from MS to MS+ marker; two
of them came directly from two vaccinees one
and three weeks after feeding, respectively, and
another one from a contact presumably infected
from the vaccinees four weeks later. Such an
experiment is still in progress together with those
of d+ and T+ markers on new isolates. At any
rate, the genetic properties of Type 3 proved not
always to be stable.
Dr. Nishizawa had an opportunity to observe
the degree of neurovirulence of the Cox monovalent
vaccine in a girl nine months old who had
been fed successively four weeks apart with the
Cox Types 1, 2, and 3 monovalent vaccines, respectively.
During the course of vaccination, she
got severe diphtheria and died 13 weeks after the
initial feeding; at that moment she had positive
antibody against Type 1 poliovirus. The autopsy
findings confirmed diphtheria and bronchopneumonia.
Pathological-morphological changes
caused by poliovirus were not recognized in the
section of the spinal cord. The virus isolation
results from the brain, spinal cord, tonsils, heart,
lung, liver, kidney, large and small intestines,
and stool in the intestines, were all negative.
From the foregoing, any type of the Cox mono-
TABLE 8.
SPREAD OF VIRUS FROM THE VACCINEES TO THEIR CONTACTS IN BOTH GROUPS, 1-4 MONTHS
OLD AND 6-18 MONTHS OLD
Age group
(month old)
No. of infants
Weeks after Leeding
1 2 5 4 5 7 7 8 10
Type 1 Type 3 Type 2
fed fed fed
6 - 18 3 vaccinees 2/3' 2/3 2/3 3/3 1/3 1/3 1/3
6 contacts 2/6 3/6 3/6 3/5 0/5 0/5 1/5
1 - 4 3 vaccinees 2/3 1 1/3 2/3 0/3 2/3 1/3
6 contacts 0/6 0/6 0/6
* Numerator: No. of virus isolations.
Denominator: No. of test samples.