LIVE POLIO IRUS VACCINES

400 Efficacy-Laboratory Evidence
TABLE 19. INCIDENCE OF EACH OF THE 3 TYPES OF POLIOVIRUS AMONG CASES OF PARALYTIC POLIO-
MYELITIS IN NON-VACCINATED CHILDREN IN THE CITY OF GUADALAJARA AT DIFFERENT TIMES AFTER
INITIATION OF VACCINATION PROGRAM
Administration of vaccine in this city was carried out on the following dates:
Type 1 from April 27 to May 30
Type 3 from June 1 to July 4
Type 2 from July 6 to August 8
weeks after onset, and in two of them six weeks
after onset of disease. Unfortunately, proper
serologic evidence is not available to discard in
a definite way the diagnosis of poliomyelitis.
The results of virus isolations from the stools of
non-vaccinated patients with the clinical diagnosis
of paralytic poliomyelitis in Mexico City
and in the city of Guadalajara are presented in
Tables 18 and 19. Table 18 shows the data for
Mexico City. It can be seen that Type 1 poliovirus
was responsible for the majority of the nonvaccinated
cases throughout the year; there were
only four cases due to Type 2 virus, but these
cases were reported before the feeding of Type
2 vaccine. It is most interesting to note the high
incidence of isolation of non-polioviruses (23 out
of 80 cases tested). Although no serologic evidence
and detailed clinical observations are available,
these results may suggest that a certain
proportion of the non-vaccinated children and
also of the vaccinated children, may actually have
not been poliomyelitis cases, but rather cases of
transitory paralysis due to other enteroviruses.
Table 19 shows the data for the City of
Guadalajara. As in Mexico City, Type 1 poliovirus
was responsible for the vast majority of the
cases among non-vaccinated children. It may be
noted that in the City of Guadalajara a high incidence
(seven out of 29 cases tested) of non-polio
enteroviruses was found in the stool of these
patients diagnosed clinically as paralytic poliomyelitis.
SUMMARY AND CONCLUSIONS
The results of the present studies indicate, first
of all, the safety of Sabin's live poliovirus vaccine.
No untoward reactions related to the feeding
of the various strains were noted among the
vaccinated children of lour different Mexican
cities and no evidence of association with vaccinated
children was found among non-vaccinated
cases.
The results of serological tests on paired sera
collected from a randomly selected group of
children before and after vaccination, show that
Sabin's attenuated strains were highly immunogenic.
The over-all antibody conversion rates
were as follows: for Type 1, 84 per cent, for
Type 2, 81 per cent, and for Type 3, 73 per cent.
The results obtained in Mexico City and in the
City of Guadalajara point out the special problems
created by the interference phenomenon
and indicate that future vaccination programs
should include at least 80 per cent of the susceptible
population in the shortest possible period of