LIVE POLIO IRUS VACCINES

512
ol
o
c,-
4
3- 0
7
Efficacy-Field Evidence
512 Eficay-Fied Evdenc
7//
W3 vaccinated regions
jjj-~ non-vaccinated regions
0-
.· II11 . 1 . .. ......I·
0-2
3-9 10 + Total AGE
FIc. 3. Poliomyelitis case rates in orally vaccinated and non-vaccinated
(Czech regions in 1959).
only briefly to those results which bear any tration of a fourth dose of Salk's vaccine in the
impact on our own study.
Plzeni region), revealed that about 40 per cent
(a) Repeated seroimmunity studies were of the most threatened child population under
made in the general population prior to the 10 years of age lacked detectable antibodies
first mass administration of Salk's vaccine at against poliovirus Types 1 and 3, while in some
the beginning of 1957 (Zácek, 2 Pesek3), and areas antibodies against Type 2 were absent in
then about eight months and one year after the about 20 per cent of the children in these age
administration of three intradermal doses of groups.
vaccine, i.e., at the end of 1958 and the begin- (b) Investigations of paried sera of children
ning of 1959, respectively. Results revealed a vaccinated with a fourth dose of Salk's vaccine
certain increase in the proportion of higher (1 ml. subcutaneously) and live oral vaccine,
antibody titers against Type 1, which may be revealed significant differences in the antibody
accounted for by the natural spread of Type 1 response between the two types of vaccination,
polioviruses in the observation period, and a particularly as regards Type 1. In children
more marked increase of antibodies against lacking homologous antibodies against Type 1,
Type 2, which can be partially explained by the after the fourth dose of inactivated vaccine,
presence of these viruses in the population. conversion occurred in 50 per cent, while after
However, in view of the lower titers, mainly in the live vaccine conversion was recorded in 95
younger children, they can also be interpreted per cent. (Significant, though less marked difby
the effect of the antigen component of Type 2 ferences, were recorded also in the remaining
of Salk's vaccine. Besides the differences de- types). The main results of these investigations
scribed above, no substantial changes in the are summarized in Table 3, which corrects the
antibody level of sera taken before vaccination preliminary results presented in our paper last
with inactivated vaccine and eight to 12 months year.
after it, were found in children aged two to 10 (c) More detailed analyses of these results
years. Investigations made at the end of 1958 made by Zácek and Vonka, 4, 5 revealed further
(before the administration of the live vaccine) significant differences in the quality and amount
and in the spring of 1959 (before the adminis- of antibodies obtained by the two vaccination