LIVE POLIO IRUS VACCINES

Epidemiological Surveillance in Mass Trial with Oral Polio Vaccine 453
the interval between vaccination and onset was
less than 28 days. One was a mumps encephalitis,
with diagnosis established by more than a fourfold
rise in titer and with known contact with
mumps. The patient with an interval of 15 days
had a titer of 1:256 for mumps, without a demonstrated
change. Two fecal examinations in MKT
were negative. The clinicians and the epidemiologist
agree that findings this year concerning nonbacterial
non-paralytic infections of the central
nervous system, are in line with usual experience.
During the period under review (January-May
1960) seven cases of paralytic poliomyelitis
were reported. (See Table 3.) (Individual case
notes are included in the appendix.) In all cases,
the clinical diagnosis was confirmed by consultants.
One suspect "abortive polio," is being carried
at present, classified as diagnosis undetermined.
Two additional cases of central nervous
system disease were carried as polio suspects, but
were proved on study not to be poliomyelitis.
Others were reported in which poliomyelitis was
considered but in which different diagnoses were
established.
It was presumed that if there should be any
hitherto unreported clinical reaction to the oral
vaccine, the clinical manifestation might well be
mild and possibly atypical. However, the five
cases observed in vaccinees were a sampling of the
usual clinical picture of polio, varying from a
minor paralysis to serious disability. Certainly,
clinically these cases could not be differentiated
from disease caused by wild polio viruses.
As previously indicated polio is not limited by
season in Dade County. In the four months, February
through May, the number of resident paralytic
polio cases with onsets in these months
were 14, 1, 3, and 16, respectively for the years
1956 through 1959. Thus in recent years, an
average of 8.5 cases had onset during this interval.
In 1960, during the same time, there were
seven paralytic cases. On the basis of frequency
alone, the occurrence of less than the average
number of cases encourages the opinion that
these may be coincidental infections, particularly
since they had the usual range of clinical manifestations.
These paralytic cases, however, had unusual
features demanding considerations. Of the seven
cases, five (71 per cent) were more than 20 years
of age. During the four years since Salk vaccine
became generally available, there have been 103
cases in Dade County, of which only 24 (23 per
cent) were in this adult age group.
The incidence of paralytic poliomyelitis in
Florida in 1960 (February-May) has been low.
Elsewhere in the State there were three cases in
these four months. During the same period in
the past four years, 37 per cent of all cases of
paralytic polio occurred in Dade County. In
1960, in contrast, 70 per cent of the 10 cases in
the State occurred in Dade County.
In the interval under study, the population of
Dade County could be divided into three groups
with respect to oral polio vaccination: (1) the
unvaccinated; (2) the recently vaccinated
(within 28 days); and (3) the vaccinated (28
days or more previously). Very preliminary figures
pertaining to these are given in Table 4.
TABLE 4.
PARALYTIC POLIO IN DADE COUNTY, FEBRUARY-MAY, 1960, IN RELATION TO VACCINATION
STATUS
ORAL VACCINATION STATUS
*Unvaccinated less than 40 years old
tRecently vaccinated less than 40
WVaccinated less than 40
Unvaccinated more than 40
PERSON
YEARS
100,000
32,000
55,000
119,000
PARALYTIC
CASES PER
POLIO 100,000
CASES PERSON YEARS
1
1
5
15.6
O 1
0.8
* Did not take vaccine.
t Had taken vaccine within 28 days.
t Had taken vaccine more than 28 days previously.