Author: Michelle Taylor, Editor-in-Chief
More than a decade after the introduction of a vaccine that has been proven to stave off 90 percent of human papillomavirus-caused cancers, only half of U.S. adolescents have completed the 3-shot series. While part of that can be attributed to adolescents and adults who question the validity of the vaccine, the majority is due to unawareness of or forgetting the need for additional doses, lack of insurance and non-frequent contact with the medical system.
But, a new study from researchers at the University of Texas Health Science Center at Houston, has revealed a single-dose regimen may be equally as effective as the current 2- to 3-dose system.
“Ensuring boys and girls receive their first dose is a big challenge in several countries and a majority of adolescents are not able to complete the recommended series due to a lack of intensive infrastructure needed to administer two or three doses,” said the paper’s senior author Ashish Deshmukh, assistant professor at UTHealth School of Public Health. “If ongoing clinical trials provide evidence regarding sustained benefits of a one-dose regimen, then implications of single-dose strategy could be substantial for reducing the burden of these cancers globally.”
Deshmukh’s study examined the difference in the prevalence of HPV infection in a total of 1620 women aged 18 to 26 of whom 1,004 were unvaccinated, 616 received at least 1 dose of HPV vaccine 106 received just 1 dose, 126 received 2 doses and 384 received 3 doses.
Compared with unvaccinated women who had a HPV infection (4-valent vaccine types [6,11,16 and 18]) prevalence of 12.5%, women who received at least one dose showed significantly less prevalence—2.4% for women with 1 dose, 5.1% for those with 2 doses and 3.1% for those who received all 3 doses.
According to the paper recently published in JAMA Network Open, there was no significant difference in prevalence for 1 dose versus 2 doses or 1 dose versus 3 doses. Additionally, differences were not statistically significant for cross protection (HPV types 31, 33, and 45), and other high-risk HPV types (HPV types 35, 39, 51, 52, 56, 58, 59, and 68).
Using a multivariable logistic regression model, the authors predicted the probability of HPV infection (types 6, 11, 16, 18) to be higher in unvaccinated women (7.4%) compared with women who received 1 dose (2.3%), 2 doses (5.7), or 3 doses (3.1%).
According to the CDC, 34,800 new cancer diagnoses are linked to human papillomavirus (HPV) annually. The virus is thought to account for more than 90% of all cervical and anal cancers, more than 60% of all penile cancers, and approximately 70% of all oral cancers. While the study authors stressed it is too early for people to rely on a single dose for protection against these cancers, they are encouraged by the results of their research.
“The current HPV vaccine dosing regimen can be cumbersome for people to understand. If one dose is proven effective in trials, the vaccine regimen will be simplified,” said lead author Kalyani Sonawane, also an assistant professor at UTHealth School of Public Health. “This will help improve the coverage rate among adolescents that are currently below the Healthy People 2020 goal and possibly will also increase the momentum of uptake in the newly approved age group.”