Obituary: Dr Jonas Salk

Jonas Salk will be remembered as the man who first showed that the dreaded poliomyelitis, or infantile paralysis, could be prevented.

Salk seized the opportunity provided by the discovery by Enders, Weller and Robbins that the polio virus could be grown in the laboratory on readily available human and monkey cells, and did not require, as had previously been thought, cells from the nervous system. This breakthrough occurred in 1949 and the discoverers won the Nobel Prize in 1954, a prize that was to elude both Salk and his great rival in polio vaccine research, Dr Albert Sabin.

Salk decided to grow the virus on monkey kidney cells in tissue culture and to treat the virus so produced with formalin; a technique he had already perfected for making influenza vaccines. The conditions of treatment were devised which destroyed the ability of the virus to grow and produce disease, but retained its ability to stimulate antibodies and protection against disease. His work was supported by the March of Dimes, part of the US National Foundation for Infantile Paralysis, which was set up in 1938 to counteract the growing concern about the increasing toll the disease was taking each summer in the United States.

President Roosevelt was the most high-profile sufferer from the disease, which greatly aided fund-raising. The National Foundation supported Salk's work and with a concentrated effort he satisfied, in a remarkably short time, the requirements for a large-scale human trial, detailed by a committee of experts under the chairmanship of Dr Tom Rivers, then the leading virologist in the US. He then set about making sufficient vaccine for a properly controlled trial in children, conducted by Dr Thomas Francis of Michigan State University Department of Public Health, and an early mentor of Salk.

In order to make the vaccine for the trial, Salk arranged to get help from the Connaught Laboratories in Toronto, then part of the University School of Hygiene. They grew much of the virus in monkey kidney tissue culture using the synthetic medium 199, which was then transported to Salk's laboratory in Pittsburgh for treatment with formalin and testing for safety and potency. The basement facilities were commonly known as the "Salk mines". The vaccine and the uninfected medium 199 was then sent to Francis for the trial. The results of the trial, announced at a press conference on 12 April 1955, showed the vaccine to be better than 90 per cent effective and catapulted Salk to fame.

Salk was rather a short man, slimly built with even then - he was 40 at the time of the trial - receding hair. He was rather a shy scholarly type, more the backroom scientist than a great public communicator. He was, however, well aware of the importance of his work and confident in the results of his careful studies. This confidence was much needed when disaster struck soon after Salk vaccine was licensed for general use in the US.

A defective batch from one manufacturer was distributed and caused 260 causes of poliomyelitis. The cause of the manufacturing problem was soon rectified, and Salk-type polio vaccine - which he liked to call non-infectious polio vaccine, but is now generally referred to as IPV (Injected Polio Vaccine) - has proved safe in practice ever since. The steps taken to ensure the safety of the vaccine led to some lowering of potency which was rectified later by workers in the Netherlands who developed improved culture technique to produce enhanced potency or e-IPV.

The use of Salk's vaccine produced a dramatic reduction in the cases of poliomyelitis in the United States, but in the 1961 the US authorities switched to Sabin's living vaccine, or OPV, because it was thought to be more effective and was easier to give by mouth to disadvantaged members of the community. Salk never gave up his advocacy of the merits of his vaccine, stressing its safety compared with OPV, which now in most Western countries causes most of the few cases of poliomyelitis that still occur.

Salk vaccine is used to control the disease in many countries in the world, especially Scandinavia, the Netherlands and France, as well as many provinces of Canada. It was a great boost to Salk when e-IPV was recognised as valuable in the US in 1981. The global eradication of poliomyelitis is now in sight, and it owes much to the efforts of Salk and Sabin, although it is the use of mass campaigns with Sabin's OPV that the final possibility has come. It is striking that neither man sought to patent his invention.

Salk was the son of Polish immigrants to New York, where they were garment makers. Like Sabin he tried law before switching to science and medicine, which he studied in New York, before moving to the University of Michigan to receive training in virology, especially work on the influenza virus in Thomas Francis's laboratory. He then took up a Research Professorship at Pittsburgh School of Medicine, where he did his pioneering work on polio vaccine. Subsequently he moved to La Jolla and became the first Director of the Salk Institute for Biological Studies, where a magnificent set of laboratories were built. He worked there to the end of his life.

Salk switched his attention to vaccine approaches for multiple sclerosis and for Aids, but his efforts in these fields had little success. He was much honoured, especially in the US, and also in France where he was awarded the Legion d'Honneur. He was a great man as well as a great medical scientist.

John Beale

It is a strange and sad truism that one is never a prophet in one's own country and this applied in recent years to Jonas Salk, writes Professor J. S. Oxford.

At the height of his career he achieved what was thought by many scientists to be the unachievable: the conquest of polio in the United States. Even Salk had his doubts and only months before the first vaccine trial he had voiced them in a meeting in Italy. But he pressed on and within the year had tested his polio vaccine in volunteers. There were serious setbacks in the years following but he had the personal courage to press ahead, to take risks.

In recent years, at least in the US and Europe, polio is rare but HIV- 1 infection is not. Ten years ago Salk applied his chemical inactivated vaccine technology (known as killed virus technology, such as he had used against polio) to HIV. In the 1950s the March of Dimes had thrown money at the polio problem and supported Salk. But this time around the situation was more difficult. The scientific world had changed and was now more molecular.

The general consensus was that it would be the biotechnologists who would provide a new vaccine against Aids, not old-fashioned "steam virologists". But then Salk would not have achieved his polio success if he had followed consensus. I understood this when we dined together a few months ago at an Aids Meeting in the United States.

It was notable how reticent his fellow American scientists were with him and his idea of a killed virus against Aids. I admired him because in spite of his "name" he was not chairing a principal session but was tucked away in a corner with a poster covered in data and patiently explaining his work to scientific virologists. But a quick meal with him in the hotel showed what a hero he was to the public at large. Salk hosted the dinner for six people to bring together scientists from around the world interested in preparing killed vaccines against Aids. It seemed a very small group of scientists for such a big topic and emphasised to me what a struggle it was now to apply classic virology rather than recombinant DNA technology to new vaccines.

Salk was his usual combative self, not at all octogenarian. He and his son were full of ideas. We proposed a toast at the end of the dinner to "the conquest of Aids". But he would have none of it. "Let's hurry," he said, "or we'll miss the evening scientific session."

Jonas Edward Salk, virologist: born New York City 28 October 1914 ; Director, Salk Institute for Biological Studies 1963-75, Resident Fellow 1963-84, Founding Director 1975-95; co-founder, Immune Response Corp 1986; married 1939 Donna Lindsay (three sons; marriage dissolved 1968), 1970 Francoise Gilot; died La Jolla, California 23 June 1995.