21 per cent of cancers worldwide are due to infections, and 60 per cent of them are caused by viruses
Nobel laureate Harald zur Hausen favoured vaccination of girls and boys as a means to prevent certain cancers, which have been linked to human papilloma viruses (HPV).
Talking to The Hindu here on Monday, Prof. Hausen, who won the Nobel Prize in Medicine in 2008 for his discovery of HPV causing cervical cancer, said 21 per cent of cancers worldwide were due to infections and 60 per cent of them were caused by viruses. The rest were due to bacteria and parasites.
He was in the city to attend the 11 edition of BioAsia and to deliver a lecture at the Centre for Cellular and Molecular Biology (CCMB).
Asked about the controversy over HPV vaccine and reports of the side effects, he said the side effects were extremely low -- one in 100,000. He said the vaccine was first introduced in 2006, and that it showed “very high efficiency”. It prevented precursor lesions of cervical cancers caused by HPV. He also discounted the claim that the vaccine would act only for five years, saying it would be effective for 10 years and more.
Prof. Hausen said prevention of lesions would drastically reduce the need for surgical interventions later, as normally such lesions would be removed through surgery. Screening would be important, especially for those who developed HPV infection, as the lesions that cause cervical cancer could be removed surgically.
He said the vaccine was also being recommended for boys because they were the transmitters of the virus. It was found that boys in 15-30 years age group have more sexual partners than girls/ women. Apart from cervical cancer, HPV is also linked to cancers of the pharynx and anus. There are almost 200 types in HPV, and 13-15 of them are linked to cancers.
He said there was suspicion that viruses caused some other cancers, too – colon cancer, childhood leukaemia and neuroblastoma in children.
Prof. Hausen said lack of sufficient screening was one of the main reasons for the high incidence of cervical cancer in India and other developing countries. Pap smear test reduces the rate by identifying the lesions that could be surgically removed. Australia has done very well in containing cervical cancer, and there has been a decline globally, barring few exceptions.
On anti-viral drugs, he said currently they were available for Hepatitis B and C viruses, besides HIV. The results in relation to HPV have been disappointing. But, condoms have been found to have prevented 40 per cent of HPV infections, he added.