Gong Gong says

This is a posthumous blog of our father's (Lim Kok Ann) life. When our father passed away on 8 March 2003, he left behind an unpublished autobiography. We'd like to celebrate his life by sharing his autobiography through this blog.

"I have dredged these anecdotes from memory just to pass the time; if they amuse my grandchildren their purpose will have been served; if they provide any instruction, it will be a happy coincidence; that they are disjointed is probably to be expected.

Aurora was the name of my grandfather’s house in Kulangsu.   Amoy, where I spent the first five or six years of my life.   I still have vivid memories of events that took place when I was barely three years old.

Lim Kok Ann
October 1996"

Sunday, December 21, 2008

4:3 Sabin Vaccine

WHO appointed me a member of the International Panel of Experts on Virus Diseases, and designated our department a Regional Enterovirus Centre. In 1962, the Minister of Health appointed me a member of its Poliomyelitis Committee that was tasked with the problem of preventing a recurrence of the polio outbreak of 1958 when there were more than 400 cases. The possible use of the Salk vaccine was soon ruled out; apart from the cost of the vaccine, the prospect of organizing an immunization programme involving the injection of over 300,000 children, our target population, was forbidding. We could be causing more cases of hepatitis through faulty sterilization of syringes (disposable syringes were not yet available then) than the polio cases we were hoping to prevent.

Note: Salk vaccine, pioneered by Jonas Salk, was made by treating poliovirus with heat and formalin until it was not able to cause disease. Because the inactivated virus did not grow in the body, a large amount of virus had to be inoculated to stimulate antibody production. Sabin vaccine was a live virus unable to cause paralysis, but because it grew in the intestines of vaccinees, a much smaller amount of virus needed be used to give protection.

The use of the Sabin oral vaccine had to be considered. This was made of polioviruses; one of each of the three types, that had been passaged many times in tissue culture and had lost their ability to cause paralysis in monkeys when inoculated by the most sensitive route. WHO had not yet declared the vaccine “safe”; although hundreds of thousands of children had been given the oral vaccine in field trials without getting polio, there lingered a suspicion that the vaccine virus could revert to pathogenicity as it was propagated to make vaccine, and actually cause poliomyelitis in the children it was meant to protect Many of the field trials had been done in the Soviet Union and the Soviets were waiting for the blessing of the WHO Poliomyelitis Committee of which I was a member (representing Asian countries!) before recommending to their government the general use of the vaccine.

“So far the vaccine has caused no polio cases,” complained the senior Russian at one meeting, “how many more trials do you want me to do before saying the vaccine is safe?” He was not going to take the blame if the child of a Party cadre got polio from the vaccine he was going to dish out. In Singapore, similar doubts of vaccine safety were raised and as mentioned earlier, it was suggested that we should wait until the vaccine was shown to be safe, rather than use Singapore children as guinea pigs in the first “mass use” of oral polio vaccine.

I relayed to our Committee the advice that Melnick had given me and which was mentioned above. There was no question in my mind that if we did not start soon to immunise the children that had been born since the 1958 outbreak, another polio outbreak would take place, engendered in the same way as the previous outbreak had been. I gave as the “considered opinion” of the Professor of Bacteriology that the Sabin vaccine should be used, and said that our department would monitor all children who developed polio-like symptoms to determine whether it was possible the oral vaccine had caused these symptoms, taking into consideration the time factors. It was a necessary spur to get theMinistry of Health going, and I believed that putting my head on the chopping block if anything went seriously wrong in the use of the vaccine was part of my job.

The vaccine was obtained through WHO initially and later from commercial sources under licence by Dr. Sabin who oversaw by correspondence the early use of oral poliovaccinc. Lee Liang Hin diluted the concentrated vaccine stocks which we mixed and dispensed in eye-dropper bottles so that one drop was the required dose for each administration of vaccine. The government polioimmunization programme was earned out in two phases. In phase 1, children between six months and two years of age were given two doses of polio vaccine at one month’s interval, reaching about 70%of the target population. In the second phase, the “routine programme”, children three months old would be given three doses of polio vaccine at monthly intervals, then two doses at four years of age and finally two doses 7 to 8 years of age on entering primary school. We joined the teams of Ministry of Health nurses who visited Maternity and Infant Welfare clinics to immunise young for the purpose, and took careful notes of the names and ages of children to whom the vaccine was given, and other useful details.

This vaccination regime so effectively reduced the incidence of polio in Singapore that the surgeons whose specialty was tendon transplantation to remedy muscle weakness had to turn their hands to other skills and hospital swimming pools for treatment and rehabilitation of polio patients were closed. Meanwhile, all cases of suspected polio were closely followed by Ministry of Health doctors who took stool specimens and blood samples for us. If we isolated a poliovirus, we tried to find out if it was a vaccine virus or not (very often it was) though the technique was difficult. From the date of onset of symptoms we back-tracked and determined if it was likely that the symptoms were vaccine-related, supposing the child had been given oral poliovaccine. Our fmding was that every child that actually developed polio had not been givenpoliovaccine recently, and as a corollary, we found that children who had received the full course of three doses of poliovaccine never developed poliomyelitis. This result eminently justified the great effort and expense the Ministry of Health invested in the polio immunization programme. In my Diploma of Public Health class, the doctors from neighbouring countries would ask when their country should start to use oral poliovaccine. My advice to them was to find out what their government was spending on treatment and rehabilitation of polio patients. I said, “When the cost of treating polio becomes greater than the estimated cost of buying and distributing the vaccine it will be time for you to adopt a polio immunization programme.”


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