HPV vaccine eff ect: is the glass half full or half empty?

1report a decrease in precancerous cervical lesions in girls younger than 18 years after population-wide human papillomavirus (HPV) vaccination in Victoria, Australia, in 2007. The study reports a 0·38% absolute decrease in the rates of histologically confi rmed high-grade cervical lesions in these girls during the 2 years after HPV vaccine introduction compared with the 3 years before vaccine introduction. 1 This ecological fi nding might be an early sentinel of the potential real-life eff ect of the vaccine on the main outcome in the clinical trials: cervical intraepithelial neoplasia of grade 2 or worse (CIN2+). However, these results should be viewed with caution, in view of the well-known limitations of ecological studies. For example, guidelines that emphasise less aggressive management of low-grade cytology, which were published 9 months before HPV vaccine introduction, could have contributed to the reported CIN2+ decrease. 2 Health-care providers might also have screened and managed vaccinated patients less aggressively, especially girls younger than the recommended screening age of 18 years. With the 47·5% relative decrease in the incidence of high-grade cervical abnormalities recorded in girls younger than 18 years, a similar though smaller decrease would be expected in girls in the next oldest age group (those aged 18–20 years), who were likely to benefi t from the vaccine and in whom vaccine coverage was high. However, no decrease was observed in this age group. Australia was the fi rst country to launch a national HPV vaccination programme with a predominantly school-based strategy. The three-dose vaccine coverage for girls aged 14–15 years in 2007 was about 72%. 3