LIVE POLIO IRUS VACCINES

Epidemiological, Virological Survey Following Oral Administration 137
m
ZO
4
1 1
1 1 PERIOD OF VACCINATIONS
- 4 REGION I
_ . - I
REGION II
28
24
20
16
12
8
4
REGION
III
24
REGION IV
32
REGION V
1957 r 1958 1 1959 J
FIG. 3.
Number of reported cases of poliomyelitis (irrespective of virological confirmation)
during 3-month periods.
the incidence in the Leiden region has usually
been lower than elsewhere, with the exception
of the two cases of non-paralytic Type 2 poliomyelitis
in 1959, which have already been discussed.
Several poliovirus strains isolated from patients
and several strains excreted by vaccinated individuals
during the same period have been examined
for T marker and neurovirulence in
Cynomolgus monkeys following intracerebral inoculation
into the right thalamic region of 1 ml.
of fluid of the first or second monkey-kidney culture
passage.
The T marker has been examined by inoculation
of ten-fold dilutions of monkey-kidney culture
virus into eight monolayers of trypsinized