LIVE POLIO IRUS VACCINES

8
General Considerations
from accepting the product. The idea of disqualifying
a live vaccine because it contains an
extraneous virus not known to be a human pathogen
immediately suggests the following considerations:
1. Almost every attempt to isolate a viral agent
from the living tissues of any organism has
succeeded, and we see no end to this interminable
path.
2. Smallpox vaccine has been used successfully
for almost 200 years. Yet extraneous viral
agents could doubtless be found if searched for
in calf lymph. Do we call a halt to vaccination
on this account?
3. Live vaccines prepared from chick-embryo
tissue could very well contain a chicken-cancer
virus. The existence of an agent of this type has
already been demonstrated by Rubin 31 in cultures
of presumably normal fertile hen's eggs.
How, therefore, does the question of the injectable
17D vaccine or chick embryo smallpox virus
enter into this picture?
The polio vaccine is administered orally, and
many viruses find their way into the human body
through the mouth. If one wishes to be a purist
in this entire matter, then the Food and Drug
Administration should be requiring that all food
items which are eaten uncooked be tested for the
presence of viral agents.
As a scientist, I support continued investigations
into the meaning of the viral agents that lie
dormant in the cells of all living organisms and
which can emerge when such cells are cultivated
under conditions freeing them from the restraining
influence exerted by the organism as a whole.
If anyone is looking for a self-perpetuating project,
here is a good one for the next thousand
years. Moreover, the particular non-polio viral
agents that may have been uncovered from live
polio vaccine have perhaps undergone more
rigorous safety tests than any other biological
agent through its extensive use in millions of
individuals throughout the world. If an adequate
number of persons exposed to these agents has
been shown to develop specific antibodies without
any clinical disease, the evidence should be
regarded as overwhelmingly in favor of the harmlessness
of these agents.
Interference. Early in our studies, we observed
that the simultaneous administration of two types
of attenuated virus led to interference between
the types.32
These observations indicated that simultaneous
immunization with all three types of poliovirus
might not be feasible. Cox and his associates 33
later reported that the difficulty presented by
simultaneous feedings had been overcome by the
use of larger doses of virus. However, our recent
observations and the large-scale observations of
Smorodintsev with other strains 34 support the
earlier findings that strains of virus administered
simultaneously interfere with each other. The
phenomenon of interference between strains also
TABLE 1.
SUBJECT
2
5
7
8
9
13
14
PERSISTENCE OF ANTIBODIES TO POLIO
10 YRS. AFTER VACCINATION
TYPE 2 TITER POST-VACC.
8 yrs. 10 yrs.
128 256
32 16
64 >1024
64 256
128 256
16 64
16 16
foreshadowed one of the problems of immunization
with attenuated virus, namely, interference
against poliovirus caused by pre-existing infection
of the intestinal tract with other enteric
viruses. 3 5 , 36 37 Whether the adverse action of
interference can be changed into a beneficial one
through the use of homotypic attenuated virus
during a polio epidemic remains to be seen, although
those who would approach such a project
with enthusiasm should be warned that the antagonists
of live virus vaccination have two pat
comments on any outcome of such a trial: If the
epidemic is substantially abated, the vaccine
failed to stop it completely; if the epidemic ends
following vaccination, it would have stopped anyway,
even without the use of vaccine. Tertiurn
non datur.
Perseverance or Obstinacy. Table 1 should
bear the caption provided 200 years ago by
Laurence Sterne: "'Tis known by the name of
perseverance in a good cause, and obstinacy in
a bad one." Here you see the Type 2 antibody
levels in the sera of children who were fed the
TN virus 10 years ago. Does the remarkable
persistence of immunity classify this as "perseverance"?