A new study reveals that the quadrivalent HPV catch-up vaccine was most effective against cancer risk in women who received the first dose between the ages of 14 and 20 years.
The US Centers for Disease Control and Prevention (CDC) recommends that children between 11 and 12 years of age receive the human papillomavirus (HPV) vaccine to prevent against certain cancers. If vaccination is not administered at that time, catch-up vaccination is recommended for females between 13 and 26 years.
In a new study assessing the effectiveness of HPV catch-up vaccination, investigators found that 3 doses of the quadrivalent catch-up vaccine was most effective in women who received the first dose between the ages of 14 and 20 years.
“The current guidelines recommend 3 doses for girls who start the vaccine series after their 15th birthday up until the age 26,” Michael J. Silverberg, PhD, MPH, research scientist in the division of Research at Kaiser Permanente, Oakland, California, told Contagion®. “Our results provide new information that this practice may not work as well for women who start between the ages of 21 and 26.
For their study, published in The Lancet Child & Adolescent Health journal, investigators aimed to determine the risk of cervical intraepithelial neoplasia (CIN), CIN3, adenocarcinoma in situ, or cancer (CIN2+ or CIN3+) by looking at prior HPV vaccination status, age at first dose, and number of doses received.
The team of investigators utilized data collected from women enrolled in Kaiser Permenente Northern California, an integrated health care delivery system. The study compared 4357 individuals who were confirmed to have CIN2+ of CIN3+ with 21,773 age-matched controls who did not have any form of CIN. For each case, 5 controls were randomly selected. The individuals were categorized by age at the time of first HPV quadrivalent vaccine dose: 14 to 17 years, 18 to 20 years, and >20 years.
The investigators found that 1 or more doses of the HPV vaccine provided protection against CIN2+ (adjusted rate ratio [RR], 0.82; 95% confidence interval [CI], 0.73-0.93) and CIN3+ (RR 0.77; 95% CI, 0.64-0.94).
When analyzing risk for CIN2+, investigators noted a decreased risk in women of all ages when at least 1 dose of the HPV vaccine had been received (RR, 0.82; 95% CI, 0.73-0.93). Women who had received at least 3 vaccine doses and had received their first dose between the ages of 14 and 17 (RR, 0.52; 95% CI, 0.36-0.74) or 18 to 20 (RR 0.65; 95% CI, 0.49-0.88) were found to have the strongest protection against CIN2+.
Girls who received their first HPV dose between the ages of 14 and 17 years were found to have a decreased risk for CIN3+ (RR, 0.44; 95% CI, 0.26-0.74). The investigators did not observe a decreased risk for CIN3+ in any of the populations when less than 3 doses of the vaccine had been administered. However, decreased risk for CIN3+ was observed for the populations aged 14 to 17 (RR, 0.27; 95% CI, 0.13-0.56) and 18 to 20 years who had received 3 or more doses of the vaccine (RR, 0.59; 95% CI, 0.36-0.97).
Neither analysis noted a statistically significant decrease in risk of CIN in women who were older than 21 years of age who had received the vaccine when stratified by age.
Out of the total number of study participants, only 23 women were diagnosed with cervical cancer and only 3 had received prior HPV vaccination; all were over the age of 21 at time of first dose.
The investigators conclude that catch-up quadrivalent HPV vaccination with 3 doses proved to provide effective protection against CIN2+ and CIN3 in participants between the ages of 14 and 20 at time of first dose, but not for women 21 and older. However, more research is needed to determine the effectiveness for individuals between the ages of 21 and 26, according to the investigators. Additionally, because this study was conducted in a single health care setting, the results may not represent all populations.
“Before a change in practice is recommended it will be important to replicate these findings in other settings,” Dr. Silverberg stressed. “In particular, it is unknown if the same results would hold for women vaccinated with the new nonavalent HPV vaccine.”