A report in yesterday’s New York Times shows a dramatic drop in the prevalence of human papilloma viruses amongst teenage American girls over the past decade. HPV causes cervical cancer and genital warts. Experts ascribe the drop to the use of the HPV vaccine. In fact, the drop is steeper than predicted because the minority of girls using the vaccine seem to have made their peers less likely to contract HPV as well — an effect known as herd immunity. Readers will remember that we have often reported on legal challenges to block poor girls from having access to these vaccines in India (they are used very widely throughout the private sector so the debate centres on use by governments). In twenty years’ time will girls in India ask why their parents left them at the highest risk in the world of contracting cervical cancer or will girls in the US ask their parents why they were pushed to have a shot at age thirteen? The verdict of history will be interesting