LIVE POLIO IRUS VACCINES

18. PRELIMINARY REPORT OF EPIDEMIOLOGICAL SURVEILLANCE
IN A MASS FIELD TRIAL WITH ORAL POLIO VACCINE*
G. M. ERICKSON, M. E. FLIPSE, A. W. MENZIN, L. B. CLAYTON,
R. E. MARKUSH, AND A. V. HARDY
Dade County Department of Public Health; Section of Preventive Medicine and
Public Health, University of Miami School of Medicine; and the Florida State
Board of Health with the cooperation of the Dade County Medical Association
DR. ERICKSON (presenting the paper):
INTRODUCTION
In considering the possibility of studies of oral
polio vaccine in Dade County, it was recognized
that no one could predict how many residents of
this American community would be willing to
take a vaccine containing attenuated living poliovirus.
Wide acceptance was essential to make it
possible to conduct a mass field trial. The response
far exceeded the most optimistic expectation.
A total of 412,000 participated within a
period of three months. The recommendation
was that all residents of Dade County less than 49
years of age participate, and that older persons
and non-county residents would be discouraged.
but not refused. Pending final tabulations of
data, the proportions of the different population
groups taking the vaccine are not known, but it
is apparent that at least two thirds of the resident
population less than 40 years of age did so.
The major objectives of the study were to
measure the individual's immediate response to
the trivalent vaccine and to determine its longrange
efficacy in the prevention of polio in the
community. There was particular interest in
examining the possibility that oral vaccination,
through providing immunity to enteric poliovirus
infection, would effectively prevent spread in the
community and, through its wide use, virtually
eradicate the clinical disease. It was believed
essential to determine whether the response in
this country would be in line with the favorable
reports on mass field trials in other countries,
as presented to the First Conference one year ago.
* Supported in part by a grant from the Lederle
Laboratories Division of the American Cyanamid
Company, Pearl River, New York.
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The use of a placebo was neither considered
indicated nor practicable. Community acceptance
would be influenced unfavorably if the public
realized that only half were receiving vaccine.
Possible spread of live attenuated virus from vaccinated
to unvaccinated individuals would make
it difficult to delineate a control group. In addition,
withholding a presumably effective vaccine
from half of the eligible population implied that,
at the rate of incidence in recent years, about
15 cases per year of paralytic poliomyelitis
might needlessly occur. Indeed, the study was
accepted with enthusiasm by the medical society
and the county health department, since they
were impressed by the published reports and by
the recommendation of consultants, which indicated
that oral vaccine probably would provide
a particularly effective protection against polio.
The interest was to test a promising vaccination
program; this, rather than a placebo-controlled
field study, was acceptable.
For the evaluation of oral polio vaccine it was
concluded that a particularly exacting and prolonged
epidemiological surveillance in a mass
field trial was the urgent necessity. The multiple
and extensive field trials in Latin America
were done where available medical and public
health resources were not always adequate to
assure exacting surveillance. Published reports
from the USSR and elsewhere have recorded
progress in the administration of oral vaccine,
but have provided less than a satisfying amount
of detail on epidemiological surveillance. There
have been detailed clinical, laboratory, and
epidemiological observations in limited field
trials, such as in Minnesota, but the small number
of persons involved would not permit any defini-