LIVE POLIO IRUS VACCINES

Epidemiological, Virological Survey Following Oral Administration 135
539 586 353 368
200
190
180
170
160
150
140
130
120 1I
110 I /
100 t
90 -
80 1'
60 I V
11 1
40 ¡ 195 6-
1: ~ * 1955 .. ..
50 1
1 po
1
1955
30
11 III IV V VI VII VIIl IX X Xl XII MONTH
Fic. 1. Number of reported cases of poliomyelitis in The Netherlands, 1955.1959.
tion trials, neither in Region I, nor in the other been reported in Region I, which are reflected in
regions.
a relatively high morbidity rate in an area with
This is also evident from the morbidity rates a population of only 150,000. Poliovirus Type 2
as recorded in Fig. 4, with the exception, how- has been isolated from two of these cases, but
ever, of the fourth three-month period of 1959 the other two were probably not due to polioin
Region I. During this period, four cases have virus infection, since we failed to isolate virus