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BART ROMBAUT AN. R. ACAD. NAC. FARM.

factors involved in limiting the infection to a systemic, inapparent
one, primarily involving the oropharynx and the intestinal tract;
(2) what interactions spell progression to disease of the central
nervous system and paralysis; and (3) why is there a difference in
frequency of paralytic disease when infection occurs between
younger and older children?

THE AGE OF VACCINATION

In 1916, the worst polioepidemic known in history was spreading
throughout the U.S.A., afflicting more than 27,000 persons with a fatal
progress in 6,000 cases, in New York alone. Little was known at this
time about the pathogenicity of poliomyelitis. This 1916 U.S.A.
epidemic gave great impetus to polio research, particularly in the
U.S.A. Additional psychological backing for polio research came from
an episode, which started in 1921, when the great Franklin D.
Roosevelt contracted poliomyelitis. Roosevelt supported all measures
that had hope of leading to a healing or prevention of the disease. Yet
even in the twenties and thirties of the 20th century, promising results
from polio research were very meager. The early therapeutic
approaches using drugs were the cause of much frustration. This in
contrast to the enormous success in the therapy of bacterial infections
with antibiotics, following the discovery of penicillin by A. Flemming
in 1928. Many drugs or chemicals were tested in the laboratories,
none proved to be of any therapeutic value. Finally, it became clear
that the only hopeful method to conquer the threat of poliomyelitis
would be the development of an efficient vaccine (7). However, one
has to realise that vaccinology was even in the mid fifties of the 20th
century a very young discipline, and that at that time the knowledge
on poliovirus and poliomyelitis was mainly clinical.

One of the main problems in developing a vaccine against
poliomyelitis was the necessity to have a susceptible tissue, in which
sufficiently large quantities of virus could be grown. At the end of
the fourties of the 20th century, a landmark in the development of a
vaccine came when Enders, Weller and Robbins (9) showed that
poliovirus could be isolated and readily propagated in cell cultures
of non-neuronal human or monkey tissue.

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