New York, April 22 : While the current standard for the human papillomavirus (HPV) vaccine in women is a three-dose regimen, even a single dose is highly effective and provides up to 98 per cent protection, according to a study. In a randomised controlled trial of 2,275 women in Kenya, the researchers found that even after 18 months, the bivalent vaccine was 97.5 per cent effective against two strains of HPV, and the nonavalent vaccine was 97.5 per cent effective against two strains of HPV. The nonavalent vaccine was also 89 per cent effective against seven strains of HPV. Even if women tested positive for one strain of HPV, the vaccine protected them from other strains of the virus. "The single-dose efficacy was the same as multiple doses, said Ruanne Barnabas, chief of the Division of Infectious Diseases at Massachusetts General Hospital in Boston. Barnabas was a professor of global health at the University of Washington School of Medicine in Seattle at the time of the study. The results were published in the journal NEJM Evidence and also presented at the 35th International Papillomavirus Conference in Washington, DC, this week. "These findings are a game-changer that may substantially reduce the incidence of HPV-attributable cervical cancer and positions single-dose HPV vaccination as a high-value and high-impact public health intervention that is within reach for us," said Professor Sam Kariuki, acting director general at the Kenya Medical Research Institute, where the study was conducted. However, the researchers said more studies are needed to test how long the vaccine lasts. HPV vaccines are a powerful tool to reduce cervical cancer that kills a woman every two minutes worldwide. Currently, just 15 per cent of women worldwide are vaccinated against HPV, the most common sexually transmitted infection (STI). The World Health Organization aims to vaccinate 90 per cent of 15-year-old girls against HPV by 2030. /IANS