LIVE POLIO IRUS VACCINES

25. VACCINATION AND CHALLENGE-POLIOMYELITIS IN
NICARAGUA, 1959-1960
JUAN JosÉ ALCOCER, M.D., ROBERTO ARMIJO, M.D., AND
MAURICIO MARTINS DA SILVA, M.D.*
Dr. ALCOCER (presenting the paper): In a
report presented at the First International Conference
on Live Poliovirus Vaccines in Washington,
D. C., 22-26 June 1959,1 we gave an
account of the history of poliomyelitis in Nicaragua,
and described in detail the oral vaccination
program in the City of Managua, carried
out during an epidemic of poliomyelitis in
1958. The epidemic started in Managua in May
and extended to 14 of the 16 departments of
the country. It lasted five months, during which
time 237 cases were reported, 98 of which were
from Managua. The attack rate in Nicaragua
in 1958 was 18.4 per 100,000 population with a
case fatality rate of 7.1 per cent. It was established
that the epidemic was due to poliovirus
Type 2.
The vaccination program started in September
1958 and included children between two months
and 10 years of age in the City and the Department
of Managua. Mass vaccination was followed
by a maintenance program, which was
intended to immunize newborn infants in maternity
hospitals and health centers in the City
of Managua with a liquid trivalent vaccine. Up
to 15 May 1959, a total of 59,855 children had
received the Type 2 virus, 54,732 the Type 3
virus, and 49,585 all three types. On the basis
of information available at the time of the vaccination
campaign it was estimated that 98, 91,
and 82 per cent of the eligible population under
10 years of age, in Managua, had received vaccine
for Types 2, 3, and 1 respectively. However,
using the revised population and age distribution
data for the Department of Managua
in 1959,2 the actual coverage was 67, 61, and
56 per cent for Types 2, 3, and 1, respectively.
* Dr. Alcocer and Dr. Martins da Silva (Pan
American Health Organization/World Health Organization);
and Dr. Armijo (Ministry of Public Health,
Managua, Nicaragua).
547
The serologic studies showed that of those children
who were seronegative at the time of vaccination,
74 per cent responded to Type 1, 58
per cent to Type 2, and 80 per cent to Type 3
polioviruses. No illness attributable to the vaccine
was observed and it was gratifying that
during the eight months following the vaccination
program, no cases of paralytic poliomyelitis
were reported in Managua.
POLIOMYELITIS OUTBREAK IN 1960
The maintenance program continued throughout
1959 and 1960 using the trivalent vaccine
which contained approximately 106.1 TCD,,o
of each of the three types of poliovirus in a 2
ml. dose. By 15 April 1960 a total of 73,533
children under 10 years of age, including 5,344
newborns, had received the oral vaccine (Table
1) on page 48. In mid-1959, in anticaption of the
seasonal epidemic exacerbation of the disease,
which has been experienced in Managua since
1938, the health authorities of Nicaragua expanded
their surveillance activities, in the course
of which three unreported paralytic cases of poliomyelitis
in 1959 were uncovered in Managua;
one had onset in January, one in May, and one
in June (Fig. 1) on page 47. This finding requires
correction of the previous statement that
no cases occurred in Managua between 15 October
1958 and 15 June 1959. From 23 August to
10 October 1959, seven additional cases were
notified in the City of Managua. After a quiet
period of 10 weeks a new upsurge in notified
cases prompted the health authorities to request
the cooperation of the Pan American Sanitary
Bureau for diagnostic assistance and additional
supplies of vaccine. Reports of cases continued
to increase in Managua and epidemic outbreaks
appeared successively in the departments of
Granada, Masaya, Chinandega, León, and Rivas,