Between June 2015 and February 2018, our program recruited 2,380 eligible participants. Only one individual per family was included in the data analysis. The total sample size was 1,787 unique participants. The Tiempo de Vacunarte program had an overall initiation rate of 67.1% and a completion rate of 39.8% [11]. Table 1 shows the demographic characteristics of our participants. The mean age of the children/adolescents group (9-17 years old) was 12.2 years (SD=2.653). The majority of the children/adolescents were Hispanic (96.02%), female (53.75%), and born in the U.S. (73.19%). The mean age of the young adults (18-26 years) was 22.2 years (SD=2.745). The majority were also Hispanic (96.57%), female (72.45%), had a greater than high school education (85.53%), married (68.27%), and were born in the U.S. (64.84%). When comparing children/adolescents to young adults, the young adult age group had a higher proportion of females (72.45% vs. 53.75% P<.0001) and more non-Hispanic whites (3.11% vs. 1.64% P<.0001). Children were more likely to be born in the U.S. compared to adults (73.15% vs. 64.84%, P<.0001) and have resided in the US for less than or equal to 10 years (55.15% vs. 34.62% P<.0001).

The unadjusted logistic regression exploring the covariates of HPV vaccine completion showed that young adults were less likely to complete the vaccination series (OR: 0.98, 95%CI: 0.96-0.99, P=0.012) compared to children/adolescents. However, in both age groups, we found that those born in Mexico were more likely to complete the vaccination series (young adults: OR: 1.40, 95% CI: 1.03-1.89, P=0.030 and children/adolescents: OR: 1.51, 95% CI: 1.03-1.89, P=0.013). Details of vaccine uptake covariates have been published previously (Molokwu et al., 2019). See Table 2.

We examined the navigation notes from calls for n=1,047 participants with 2,084 navigation notes. The five barrier themes that emerged were failure to contact, scheduling concerns, ineligibility, completed series outside of the program, medical concerns, and miscellaneous (see Fig. 1). The average number of barriers identified per participant, regardless of age group, was 1.49.

Frequency and percentage of barriers categories for Tiempo 1 participants, El Paso County, TX, 2015-2018 (n=2,084)

The inability to contact participants for follow-up was the most significant barrier our project staff faced in navigating participants to completion of the HPV vaccination series (n=1,801, 86.42%). As part of the program development, we identified the transient nature of our population as a possible barrier. We tried to ensure we had accurate contact information, such as collecting multiple contacts for each participant. Despite these efforts, we still had difficulty contacting many of our participants. The typical navigation comments documented included “Phone number of participant and contact person both out of service” or when a response was received. “Person that answered phone stated that the phone number was not ‘participant name’. Participant’s contact provided the ‘correct’ phone number. However, when I called, there was no answer, and we were unable to leave a message”. While also coded as failure to contact, there were several participants who chose to no longer engage with the program and hung the phone up when called “Called to try to schedule the participant’s children’s last vaccine. Participant answered then hung up without talking to me” and “Patient hung up on me mid-sentence when I called again there was no answer. We were, therefore, unable to identify any additional barriers in these participants.

Approximately 5% of contacts had difficulty scheduling follow-up appointments. The navigators identified scheduling difficulties, including conflicts with work schedules, school schedules, and being out of town on vacations, as well as other miscellaneous scheduling conflicts. Common scheduling comments identified in navigation notes include; “ The Participant said that she has Tuesday and Wednesday off from work; however, it would be better if we scheduled in two weeks”; “Spoke with participant and she stated that she works late every day and that they will call us back to try to schedule an appointment for next week”; “The participant is interested in the vaccine, but she is now working out of town; she will call back when she is back”; “The child, ‘participant name,’ has many activities these days and is unavailable to keep an appointment. The mother then refused the vaccine for the child.” These scheduling conflicts were sometimes overcome by scheduling home visits for vaccination, which is not always possible in real-world applications.

A total of 3.55% (n=74) were marked as ineligible at some point in the program. Again, it highlighted the difficulty in providing vaccines or other preventive services to a mobile and hard-to-reach population. Common reasons noted on navigation were no longer being uninsured or underinsured or moving out of town with such reports as “The participant moved to New Mexico.” Since funding for the program required participants to have a self-identified Texas address, they became ineligible if they moved to neighboring states.

A small number of participants, about 2% (n=36), cited medical issues for not receiving the HPV vaccine. The most common medical concerns were participants who reported being pregnant following intake into the program. Navigation notes were documented; “Participant name” is pregnant, will call back after she had the baby. “spoke with pt stated she is pregnant and cannot continue to vaccinate she will call us back after her baby is born to continue doses. “

We did have a minimal number of participants who verbalized concerns about vaccine side effects they had heard from others or acute illness at the time of scheduling. While this was noted in navigation notes during scheduling, it was not identified as a barrier to receiving the vaccine.

The final 2% (n=34) of barriers were aggregated into a miscellaneous group that did not fit clearly into some of the other obstacles encountered by our navigators. These miscellaneous barriers were variable, such as “I spoke with the mother, and she told me that her daughter is in jail and she doesn’t know when she will be out” or another participant who reported, “Participant withdrew from the program and said she would no longer sign anything. She indicated that someone stole her identity and had privacy concerns”.

This was not considered a proper barrier as we had participants in the program report completion or intention to continue the vaccine series with other providers (Approximately 2%). “The mother said she will bring in ‘participant name’ to receive the third dose today. However, the mother later called back to say that she took the child to the pediatrician, and they administered the vaccine there.” However, some indicated that they were discouraged by their provider and told only to get vaccines from a doctor’s office. “Participant was called and denied our program due to her doctor advising her to only get vaccines at the doctor’s office.”