According to recent study published in the journal CANCER, the rate of high-grade cervical lesions declined in young american women since the approval of HPV vaccines. However, there is a possibility that this decline may be related to reduced screening, since the recommended age for cervical cancer screening has been increased to 21 years in the previous decade.

Cervical adenocarcinoma in situ (CIN2+) lesions and cervical intraepithelial neoplasia grade 2, 3 (CIN), can be monitored as early markers of the impact of the human papillomavirus (HPV) vaccine. In the study, a team of researchers led by Susan Hariri, PhD, MPH, epidemiologist at the department of STD Prevention in the CDC, hypothesized that changes in screening methods could affect observed reductions in CIN2+ rates and complicate the interpretation of vaccine impact.

HPV-IMPACT, established in 2008 to monitor the impact of HPV vaccination on CIN2+ through population-based laboratory surveillance, was the source used by researchers to assess data from catchments areas in eight contiguous cities in California, Connecticut, New York and Oregon, The total population of women who were 18 years old or older ranged from 230,000 to 330,000 at each participating site according to the 2010 US Census data. The analysis included data from 9,119 women with CIN2+ lesions reported between 2008 and 2012.

Results revealed that from 2008 to 2012, CIN2+ incidences decreased among women aged between 18 and 20 years (New York, from 299 to 43 per 100,000 women, California, from 94 to 5; Connecticut, from 450 to 57; and Oregon, from 202 to 37) and among 21- to 29-year-olds in Connecticut (from 762 to 589) and New York (from 770 to 465).

There were no differences in the rates among women aged 30 and 39 years. Within this period of time there was also a decline in the screening rates. The results revealed the highest decreases occurred among women aged 18 and 20 years (from 67% in Oregon to 88% in California). The lowest decreases occurred among women aged 21 to 29 years (13%-27%) and among women aged 30 to 39 year (3%-21%).

“To our knowledge, this is the first examination of trends in CIN2+ diagnosis in multiple populations of U.S. women in the new era of cervical cancer prevention,” Hariri and colleagues concluded according to a recent news release. “Importantly, our data illustrate the challenges in assessing HPV vaccine impact on cervical precancers in the U.S. and emphasize the importance of additional information such as types of HPV detected in these lesions to assist in this determination.”

“Despite the confounding effect of changing cervical cancer screening guidelines, the findings cannot be completely ignored,” wrote Dr. Brar and Dr. Allan Covens, MD, both of the division of gynecological oncology at University of Toronto. “[Hariri et al] also highlight a significant confounder that future studies need to address. With wider acceptance and standardization of cervical cancer screening guidelines and with an increasing number of women entering the vaccinated cohort, the magnitude of vaccine effectiveness should become more obvious. Further studies are needed to assess the changes in high-grade histological abnormalities in the postvaccine era. More importantly, these histological changes need to be correlated with patient-level vaccination status and population-level vaccine uptake rates”.