Merck's HPV vaccine is most effective among youths

An experimental vaccine developed by Merck to prevent the sexually transmitted human papillomavirus, which has been linked with virtually all cases of cervical cancer, is slightly more effective in young people than in older recipients, The Wall Street Journal reports. Merck officials said the vaccine, called Gardasil, produced a higher anti-HPV immune response on boys and girls ages 10-15 than in a group of women ages 16-23. The younger group had a 100% antibody response rate to three common strains of HPV after being vaccinated, and a 99.9% rate to a fourth strain; the older women had a 100% response rate to the first three strains, and a 99.1% response rate to the fourth. A previous study showed Gardasil reduced the incidence of HPV infections by 90% in a study of more than 500 women. In addition to being linked with cervical cancer, HPV infections can cause genital and anal warts in both men and women, and has been shown in some studies to boost the risk of anal cancer. Merck officials say they will seek Food and Drug Administration approval of the vaccine later this year.