In 1963, I moved to Houston with my wife Hiroko and my two children. One day, about three months later, a Japanese neighbour asked us to babysit his daughter. She was the same age as my three-year-old son and the two of them played together.
Later that evening, I noticed a blister-like rash on the girl’s head. I recognised it as chickenpox and feared she would have passed it on to my son. I knew the symptoms could be severe and that there were no effective treatments for chickenpox.
Two weeks after we had babysat the girl, my son developed a rash on his face that quickly spread across his body. His symptoms progressed quickly and severely. His temperature shot up and he began to have trouble breathing. He was in a terrible way and all my wife and I could do was to watch him day and night. We didn’t sleep. He seemed so ill that I remember worrying about what would happen to him.
But gradually the symptoms lessened and my son recovered. I realised then that I should use my knowledge of viruses to develop a chickenpox vaccine – at that point, I was in my early thirties and had spent most of my working life studying the measles and polio viruses. I had gone to Houston on a one-year fellowship with the Rockefeller Foundation to study the link between viruses and cancer at Baylor Medical College.
I moved back to Japan in 1965. At that time, there was a fear that the chickenpox virus might be linked to cancer so a vaccine could end up being carcinogenic. Some researchers also feared that while a vaccine might stop chickenpox, it could lead to the development of shingles later in life. If I was to develop the vaccine, I needed to prove that neither of these fears was true.
It took me four years, using cultured human embryo cells, to prove that there wasn’t a link between this family of viruses and cancer.
And then, because the vaccine would use a lab developed virus, I expected that symptoms of shingles caused by the vaccine would be far less severe than those caused by wild-type viruses.
I started to work on the chickenpox vaccine in 1970. At the time, live measles, rubella and mumps vaccines had been developed. The B-type hepatitis vaccine was in progress, using genetic engineering, and our field seemed to be ever‑expanding. It was an exciting time for vaccinologists.
By 1972, almost nine years after my son first developed chickenpox, I was ready to start clinical studies on the vaccine. Chickenpox usually spreads quickly through children’s hospitals but in the hospital where we conducted our trial, the spread of chickenpox was prevented. For me, it felt like a breakthrough moment.
I realised I had created an effective vaccine.
Today, the price of the chickenpox vaccine is high compared with other vaccines such as measles, rubella and polio. However, many countries, including Japan, the US and Germany, now have universal vaccination programmes. In 2009 the UK immunisation body decided against universal vaccination, first because of the cost and second because of a fear, still, that it could increase the likelihood of developing shingles later on in life. I think that fear is overstated because after the chickenpox vaccination there have only ever been very rare appearances of a mild rash. I believe that the vaccine will stop severe chickenpox symptoms in children and make it less likely that old people will get shingles. I am very proud of my and my colleagues’ work.