LIVE POLIO IRUS VACCINES

14. THE CAPACITY OF LIVE ATTENUATED POLIOVIRUSES
TO CAUSE HUMAN INFECTION AND TO
SPREAD WITHIN FAMILIES*
JOHN R. PAUL, DOROTHY M. HORSTMANN, JOHN T. RIORDAN,
E. M. OPTON, AND R. H. GREEN
Section of Epidemiology and Preventive Medicine, Yale University School of
Medicine, and the WHO Regional Poliomyelitis Laboratory for the Americas
DR. PAUL (presenting the paper): The purpose
of this report is to document the capacity of three
attenuated polioviruses to take and to spread
within families when given as a trivalent vaccine,
according to the outline of the field trial described
earlier today in the paper by Dr. Horstmann
and her colleagues.l
This work is essentially a study by the Yale
Poliomyelitis Study Unit, in which I am only a
spokesman. Others who did most of the work are
listed on the title page.
Mention has already been made of the degree
to which alimentary infection by these strains
was induced in this particular field trial, involving
as it did approximately 50 families, about the
size of Dr. Verlinde's study, although the environment
was different. The setting was in a village
in Costa Rica.
For the privilege of carrying out this study
there, we are much indebted to the Minister of
Health, Dr. Quirce, and to the Director General
of Health, Dr. Vargas-Méndez.
The strains of the attenuated poliovirus used
were kindly supplied by Dr. Cox, and are known
as the Lederle attenuated poliovirus strains.
I want to mention again that the design of the
trial called for the feeding of an index child
under the age of two years in each of 48 separate
families in which the siblings, who were all under
the age of five, were left unfed, so they could be
included in the study as susceptibles.
In other words, an object of the trial was to
see how far these polioviruses got in this particular
setting, why they got where they did, or why
* Representing studies planned and carried out by
the Yale Poliomyelitis Study Unit under the auspices
of the Pan American Sanitary Bureau and in close
cooperation with the Ministry of Health of Costa Rica.
174
not. And again may I emphasize that the objective
of this study was not to compare the
capacities of individual attenuated poliovirus
strains, but rather to consider the problem as
one of experimental epidemiology.
A special framework has been established here,
and it should be recognized from the start that the
findings reflect the effectiveness of this vaccine
when administered within this particular environment.
This is a point which Professor Stuart-Harris
made yesterday, and Professor Zhdanov has emphasized
it in his use of the term "ecology." In
other words, our study is more academic than
practical, and could be said to recall Topley and
Webster's observations of a generation ago on
experimental epidemiology in mice. Their results
were wholly dependent upon the age and
immune status of their mice, the size of the box
in which their mice were placed, its environment,
and the presence of extraneous infections.' Our
results are dependent upon similar factors.
RESULTS
A theoretical schema for depicting the in/fectability
of an attenuated poliovirus strain when
given as a vaccine is presented first in a series of
diagrams.
Figure 1 is a schematic diagram to illustrate
hypothetically the results in a group of 48 potential
vaccinees (designated by 48 horizontal
lines) who have been given two doses of triple,
live poliovirus vaccine one month apart, on 30
July and 30 August. The blank background
would indicate that the vaccine did not give rise
to antibodies in any of this group.
Figure 2 is a continuation of the diagram in
Fig. 1 to illustrate hypothetically, complete suc-