The analysis adds to a growing body of evidence demonstrating vaccine-associated changes in cervical cancer incidence and mortality.
Previous data from the United Kingdom, published earlier in November, showed that cervical cancer rates were 87% lower among girls who received the HPV vaccine compared to previously unvaccinated generations. Based on the analysis, the authors concluded that the UK’s HPV immunization program “almost eliminated cervical cancer” in women born since September 1995.
The latest study, published Nov. 29 in JAMA Pediatrics , reports a 38% drop in cervical cancer incidence and a 43% decline in mortality among young women and girls after HPV vaccination was introduced in the United States.
“These results are encouraging,” Peter Sasieni, MD, of King’s College London, and senior author on the U.K. study, told this news organization in an email.
The difference in incidence rates between the U.K. and U.S. studies, Dr. Sasieni explained, is likely due to HPV vaccine coverage not expanding as significantly in the United States as it has in the United Kingdom, and “thus one would anticipate a lower impact on the population in the U.S.”
In the U.S. analysis, Justin Barnes, MD, a radiation oncology resident at Washington University, St. Louis, and colleagues examined cervical cancer incidence between January 2001 and December 2017 using Surveillance, Epidemiology, and End Results and National Program of Cancer Registries data as well as mortality data from the National Center for Health Statistics.
Dr. Barnes and colleagues then compared changes in cervical cancer incidence and mortality between prevaccination years (January 2001 to December 2005) and postvaccination years (January 2010 to December 2017) among three age cohorts – 15-24 years, 25-29 years, and 30-39 years.
“The older 2 groups were included as comparison, given their low vaccination rates,” Dr. Barnes and colleagues explained.
Results show that between the prevaccination and postvaccination periods, the incidence of cervical cancer dropped by 38% in the youngest cohort and by only 16% in the middle-aged group and 8% in the oldest cohort.
Women and girls in the youngest group saw a striking drop in mortality: a 43% decline, which translated to a mortality rate of 0.6 per 100,000.
On the other hand, the authors report a 4.7% decline in mortality in the oldest group and a 4.3% increase in mortality in the middle-aged group – translating to a mortality rate of 1.89 per 100,000 and 0.57 per 100,000, respectively.
Overall, “these nationwide data showed decreased cervical cancer incidence and mortality among women and girls aged 15-24 years after HPV vaccine introduction,” Dr. Barnes and colleagues wrote. The changes in cervical cancer incidence and mortality observed in the youngest age group “were greater than changes in those aged 25 to 29 years and 30 to 39 years, suggesting possible associations with HPV vaccination.”
This analysis lines up with previous evidence from U.S. epidemiologic data, which “have shown decreased cervical cancer incidence after vaccine implementation in women and girls aged 15 to 24 years but not older women.”
Although “the number of deaths and hence the number of potentially averted deaths in young women and girls was small,” the study adds to the current literature by “providing suggestive evidence for vaccine-associated decreases in cervical cancer mortality,” investigators concluded.
The authors have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.