LIVE POLIO IRUS VACCINES

Epidemiological, Virological Survey Following Oral Administration 141
TABLE 2c. T MARKER AND INTRACEREBRAL NEUROVIRULENCE OF TYPE 3 STRAINS EXCRETED BY
VACCINATED INDIVIDUALS
MONKEY
NEUROVIRULENCE
VACCINEE
NUMBER
DAY AFTER
VACCINE
FEEDING
TCDo0 LOG 10
INOCULATED
DIFFERENCE
LOG TITER AT
40 ° C. AND 37 0 C
T MARKER
6
10
14
5
14
15
+-
8.0
8.2
7.9
3.0
0
4.2
I
23
26
28
29/1
29/2
114
185/1
8
8
29
36
44
19
9
+
7.6
8.4
8.0
7.8
7.2
7.1
6.3
2.3
4.8
4.4
1.0
1.2
5.5
1.0
T
T
T
I
185/2
23
+
7.0
3.5
I
188/1
188/2
191
196/1
196/2
196/3
9
29
13
12
21
27
+
+
+-
+
7.2
6.2
6.2
6.3
5.5
6.0
1.0
1.5
3.2
1.0
1.0
1.0
202/1
12
7.4
3.0
I
202/2
202/3
19
26
+
+-
6.5
6.7
3.3
0.2
I1
of one strain. Three strains excreted by vaccinee
202 possessed the T character, which was correlated
with absence of neurovirulence in those
excreted on the 12th and 18th day, whereas that
excreted on the 25th day exhibited intracerebral
activity following inoculation of 106s8 TCD,,.
Twelve of 16 Type 2 strains excreted by
vaccinated individuals possessed the T character
and four were intermediate, as recorded in Table
2B. None of them showed evidence of neurovirulence
following intracerebral inoculation of
amounts of virus as high as 104.0 to 108.4 TCD 5 0 .
A less regular pattern shows the Type 3
strains (Table 2C). Ten of 20 strains excreted
by vaccinated individuals possess the T+ character,
and six of them exhibited intracerebral activity.
Three of six intermediate strains showed
evidence of increased neurovirulence. Moreover,
one of four T strains produced paralysis after
intracerebral inoculation of 107.9 TCD 50 .
When summarizing these observations, regardless
of the types, intracerebral activity has been
shown in 2 of 33 (6 per cent) of the T strains,
in 3 of 11 (27 per cent) of the intermediate
strains and in 6 of 10 (60 per cent) of the T+
strains excreted by vaccinated individuals.
In conclusion, the genetic stability of the Type
3 vaccine strain is less than that of Types 1 and
2. Nevertheless, there has been no evidence of
any harmful effect either to the vaccinated individuals
or to the community in which all three