Salk, Jonas WORLD OF MICROBIOLOGY AND IMMUNOLOGY502•
sketching in his spare time. He and his wife, Dora Press,
encouraged their son’s academic talents, sending him to
Townsend Harris High School for the gifted. There, young
Salk was both highly motivated and high achieving, graduat-
ing at the age of fifteen and enrolling in the legal faculty of the
City College of New York. Ever curious, he attended some sci-
ence courses and quickly decided to switch fields. Salk grad-
uated with a bachelor’s degree in science in 1933, at the age of
nineteen, and went on to New York University’s School of
Medicine. Initially he scraped by on money his parents had
borrowed for him; after the first year, however, scholarships
and fellowships paid his way. In his senior year, Salk met the
man with whom he would collaborate on some of the most
important work of his career, Dr. Thomas Francis, Jr.
On June 7, 1939, Salk was awarded his M.D. The next
day, he married Donna Lindsay, a psychology major who
was employed as a social worker. The couple eventually had
three sons. After graduation, Salk continued working with
Francis, and concurrently began a two-year internship at
Mount Sinai Hospital in New York. Upon completing his
internship, Salk accepted a National Research Council fel-
lowship and moved to The University of Michigan to join Dr.
Francis, who had been heading up Michigan’s department of
epidemiologysince the previous year. Working on behalf of
the U.S. Army, the team strove to develop a flu vaccine.
Their goal was a “killed-virus” vaccine—able to kill the live
flu viruses in the body, while simultaneously producing anti-
bodies that could fight off future invaders of the same type,
thus producing immunity. By 1943, Salk and Francis had
developed a formalin-killed-virus vaccine, effective against
both type A and B influenzaviruses, and were in a position
to begin clinical trials.
In 1946, Salk was appointed assistant professor of epi-
demiology at Michigan. Around this time he extended his
research to cover not only viruses and the body’s reaction to
them, but also their epidemic effects in populations. The fol-
lowing year he accepted an invitation to move to the
University of Pittsburgh School of Medicine’s Virus Research
Laboratory as an associate research professor of bacteriology.
When Salk arrived at the Pittsburgh laboratory, what he
encountered was not encouraging. The laboratory had no
experience with the kind of basic research he was accustomed
to, and it took considerable effort on his part to bring the lab
up to par. However, Salk was not shy about seeking financial
support for the laboratory from outside benefactors, and soon
his laboratory represented the cutting edge of viral research.
In addition to building a respectable laboratory, Salk
also devoted a considerable amount of his energies to writing
scientific papers on a number of topics, including the polio
virus. Some of these came to the attention of Daniel Basil
O’Connor, the director of the National Foundation for
Infantile Paralysis—an organization that had long been
involved with the treatment and rehabilitation of polio victims.
O’Connor eyed Salk as a possible recruit for the polio vaccine
research his organization sponsored. When the two finally
met, O’Connor was much taken by Salk—so much so, in fact,
that he put almost all of the National Foundation’s money
behind Salk’s vaccine research efforts.Poliomyelitis, traceable back to ancient Egypt, causes
permanent paralysis in those it strikes, or chronic shortness of
breath often leading to death. Children, in particular, are espe-
cially vulnerable to the polio virus. The University of
Pittsburgh was one of four universities engaged in trying to
sort and classify the more than one hundred known varieties of
polio virus. By 1951, Salk was able to assert with certainty
that all polio viruses fell into one of three types, each having
various strains; some of these were highly infectious, others
barely so. Once he had established this, Salk was in a position
to start work on developing a vaccine.
Salk’s first challenge was to obtain enough of the virus
to be able to develop a vaccine in doses large enough to have
an impact; this was particularly difficult since viruses, unlike
culture-grown bacteria, need living cells to grow. The break-
through came when the team of John F. Enders, Thomas
Weller, and Frederick Robbins found that the polio virus could
be grown in embryonic tissue—a discovery that earned them
a Nobel Prize in 1954.
Salk subsequently grew samples of all three varieties of
polio virus in cultures of monkey kidney tissue, then killed the
virus with formaldehyde. Salk believed that it was essential to
use a killed polio virus (rather than a live virus) in the vaccine,
as the live-virus vaccine would have a much higher chance of
accidentally inducing polio in inoculated children. He there-
fore, exposed the viruses to formaldehyde for nearly 13 days.
Though after only three days he could detect no virulence in
the sample, Salk wanted to establish a wide safety margin;
after an additional ten days of exposure to the formaldehyde,
he reasoned that there was only a one-in-a-trillion chance of
there being a live virus particle in a single dose of his vaccine.
Salk tested it on monkeys with positive results before pro-
ceeding to human clinical trials.
Despite Salk’s confidence, many of his colleagues were
skeptical, believing that a killed-virus vaccine could not pos-
sibly be effective. His dubious standing was further com-
pounded by the fact that he was relatively new to polio vaccine
research; some of his chief competitors in the race to develop
the vaccine—most notably Albert Sabin, the chief proponent
for a live-virus vaccine—had been at it for years.
As the field narrowed, the division between the killed-
virus and the live-virus camps widened, and what had once
been a polite difference of opinion became a serious ideologi-
cal conflict. Salk and his chief backer, the National Foundation
for Infantile Paralysis, were lonely in their corner. Salk failed
to let his position in the scientific wilderness dissuade him and
he continued, undeterred, with his research. To test his vac-
cine’s strength, in early 1952, Salk administered a type I vac-
cine to children who had already been infected with the polio
virus. Afterwards, he measured their antibodylevels. His
results clearly indicated that the vaccine produced large
amounts of antibodies. Buoyed by this success, the clinical trial
was then extended to include children who had never had polio.
In May 1952, Salk initiated preparations for a massive
field trial in which over four hundred thousand children would
be vaccinated. The largest medical experiment that had ever
been carried out in the United States, the test finally got under-
way in April 1954, under the direction of Dr. Francis and spon-womi_S 5/7/03 8:20 AM Page 502