HPV Vaccine Completion Rates Lagged, Especially for Females, Study Finds

Completion of the recommended 3 doses of the cancer-preventing human papillomavirus (HPV) vaccine showed differences between sexes, with fewer girls and women finishing the series within 1 year as compared to boys and men, according to a new study published in the American Journal of Public Health.

Overall completion rates declined sharply over time in the analysis of patients with private insurance, and the authors of the study said the findings suggest that series completion deserves a renewed focus by vaccination programs.

“A lot of the focus has been on getting people to start the vaccine,” said Jennifer C. Spencer, MSPH, the lead author of the paper. This study is different because it is one of the largest to track completion rates over a long period of time, she said, questioning if starting the vaccine is enough of a push to get patients to finish it. "This study suggests that it is not," she said.

The study examined data between 2006 to 2014, when the vaccine was given in a 3-dose series. The study was conducted by using the MarketScan commercial claims database, identifying 1.3 million privately insured individuals ages 9 to 26 years who initiated the bivalent or quadrivalent HPV vaccine series, with follow-up data extending through 2015.

The 2-dose version, which became available in 2016, is only recommended for children ages 9 to 15. Current CDC guidelines call for vaccinating children between ages 11 and 12, although catch-up doses can be given as late as age 26 for women and age 21 for men.

The study's outcome measure was getting the third HPV dose within 12 months of the first, compared by year of initiation. The US Advisory Committee on Immunization Practices (ACIP) first recommended the vaccine to girls in 2006 and expanded this recommendation to boys in 2011. This study tracked those years, analyzing claims data of girls post 2006 on and of boys post 2011.

Uptake has been lower than expected, with the 2016 National Immunization Survey Teen (NIS—Teen) estimating only 32% of boys and 43% of girls aged 13 to 17 years have received the full 3-dose series.

Adjusting for age, region, insurance type, administering physician, and prior flu vaccine only increased the magnitude of these differences, the authors wrote.

The database captures people with insurance at least a year before the first dose and a year after the second dose, said Spencer, who is a doctoral candidate in health policy and management at the University of North Carolina.

Race and income were not captured as a variable in the study; private insurance was used as a surrogate for socioeconomic status.

“This ends up being a fairly well-off group of individuals, as far as they have insurance coverage,” Spencer said in an interview with The American Journal of Managed Care^® (AJMC^®). She said that suggests that low uptake in this group might hint at even lower rates in groups without insurance.

While 67% of females finished the series in 2006, only 38% did so in 2014. In between, rates fell sharply in 2007 (59%), 2008 (50.8%), and 2009 (42.1%), as did rate of completion for boys, but not as sharply: 36% finished in 2011 versus 33% in 2014.

Positive predictors of receiving all 3 doses in the first year included also receiving a timely follow-through, receiving the flu vaccine in the prior year, and receiving the first HPV vaccine dose from an obstetrician/gynecologist (OB/GYN).

Geography came into play, too—living in the South or West was associated with lower completion rates.

Which provider gave the first dose mattered, too. Females who received their &#64257;rst HPV vaccine dose from OB/GYNs were more likely to receive 3 doses within 1 year than were those seeing a pediatrician (54.7% vs 44.3%, respectively; P <.001).

Females getting their first dose from midlevel providers (such as a nurse practitioner or physician assistant) were least likely to follow through (41.4%).

Similarly, males who received their &#64257;rst HPV vaccine dose from a midlevel provider were less likely to receive the full series than were males who saw a pediatrician (31.3% vs 36.1%, respectively; P <.001).

Patients in health maintenance organization plans were less likely to follow through all 3 doses than were those in preferred provider organization plans (females, 42.4% vs 46.2%, respectively and males, 31.7% vs 36.3%, respectively; P <.001).

Females in high-deductible health plans were less likely to follow through than were those in preferred provider organizations (44.2% vs 46.2%, respectively; P <.001).

While HPV vaccine initiation has been increasing, researchers have paid little attention to changes in vaccine series completion.

In addition, uptake of the HPV vaccine has never come close to reaching the Healthy People 2020 goal of 80% completion in both boys and girls by age 15, even though HPV causes virtually all cervical and the majority of anal, penile, and oropharyngeal cancers.

Spencer elaborated on the paper’s 2 hypotheses attempting to explain the declining follow-through in HPV vaccination. Patient characteristics may have started changing in ways not captured in the study, she said, calling the providers who were giving the vaccine in 2006, and the people who were getting it, “early adopters.”

If one assumes that the population getting the vaccine became more diverse over time in terms of race, ethnicity, and socioeconomic status, it is possible that since other evidence suggests that those groups are also less likely to follow through on all 3 doses, it could be another source of the decline seen in this study, she said. (Race and income were not captured in the study).

“It’s not so surprising to see in the first few years that the people who start the series are much more activated about completing it and that you see this big drop off between 2006 and 2009, which is where we see the largest nosedive in completion rates,” she said.

Reference

Spencer JC, Brewer NT, Trogdon JG, et al; Predictors of human papillomavirus vaccine follow-through among privately insured US patients [published online May 17, 2018]. Am J Public Health. doi: 10.2105/AJPH.2018.304408.