LIVE POLIO IRUS VACCINES

Use of Sabin's Live Poliovirus Vaccine in Mexico 399
TABLE 18. INCIDENCE OF EACH OF THE 3 TYPES OF POLIOVIRUS AMONG CASES OF PARALYTIC
POLIOMYELITIS IN NON-VACCINATED CHILDREN IN MEXICO CITY AT DIFFERENT TIMES AFTER INITIA-
TION OF VACCINATION PROGRAM
Administration of vaccine in this city was carried out on the following dates:
Type 1 from February 23 to April 4
Type 3 from April 6 to May 14
Type 2 from May 15 to June 20
Month
Number of
Number of isolations of indicated type of virus
oases
Tested Type 1 Type 2 Type 3 Non polio Negativo
Maroh 9 6 3 0 0 0
April 14 10 0 0 3 1
MaJ 23 9 1 2 11 0
June 13 7 0 0 6 0
July 6 4 O 0 2 Go
August 3 3 0 0 0 0
September 5 3 0 0 1 1
October 3 3 0 0 0 0
November 3 3 O 0 0 O
December 1 1 0 0 0 0
Total 80 49 4 2 23 2
was recovered from the stool of all 16 patients
from whom specimens could be obtained; one
case developed the disease 16 days after vaccination.
Unfortunately, studies in this case are
incomplete and do not permit any conclusion as
to whether or not the child was actually infected
with a wild Type 1 poliovirus at the time of vaccination
or a few days thereafter. Studies on the
isolated strain, using the various genetic markers,
could help to clarify this point. The interval between
vaccination and onset of illness in the other
16 children was 35 to 80 days in nine cases and
more than 80 days in seven cases. On the basis
of available data, it is difficult to explain these
failures of immunization. Nevertheless, the high
incidence of infection with different enteroviruses,
which has been demonstrated in this type
of a population in Mexico (25 per cent as shown
by the tests in a small group of 12 children
studied two weeks before vaccination in Mexico
City), strongly suggests that the phenomenon of
interference played an important part in the unsucessful
implantation of the Type 1 poliovirus
vaccine.
Studies on 16 of the 17 cases reported in the
City of Guadalajara showed the following results:
Type 1 poliovirus was recovered from the
stool of six cases, in all of which, the interval
between administration of Type 1 vaccine and
onset of illness was more than 30 days; in 10
patients, a non-poliovirus was recovered from the
stools; in seven of these 10 patients, the nonpoliovirus
was isolated within the first or second
week after onset of disease, in one case three