A Missed Opportunity: Evaluating Immunization Status and Barriers in Hospitalized Children

We conducted a prospective study of children aged 2 months to 18 years admitted to the General Pediatric Medicine Clinical Teaching Units (CTU) over a 15-month period between July 08, 2021 and October 08, 2022. Participants were selected using convenience sampling because of limitations in availability of research team members. Participant recruitment occurred on weekdays and weekends, daytime, and evenings, depending on research team availability. Exclusion criteria included those transferred from pediatric CTU service to another service (for example, PICU or surgery and no longer under the care of CTU). As our hospital provides care to children from outside of the provincial boundaries, children were included in the study regardless of their postal code to ensure the results more closely represented the population we serve in our hospital. Availability of immunization records was not determined before enrollment.

Upon admission to the hospital, and after stabilization of the patient, caregivers and patients (if applicable) were briefed on the study and verbal consent was obtained for a research team member to discuss the study in more detail. A trained study team member (resident physician or medical student) then obtained written informed consent for participation from caregivers. Written assent was also obtained from children 6 years and older. Adolescents aged 15 to 17 years of age with decision making capacity provided their own written informed consent for their participation. Participant recruitment was limited to times during which a study team member was available.

Immunization and demographic data were collected from the patient’s electronic medical record. For those patients whose immunization records were not available through the electronic medical record, a member of the research team contacted individual public health units to verify records. Study data were collected and managed using REDCap¹⁶  electronic data capture tools. Immunization data collected was restricted to those vaccines included in the provincial routine immunization schedule and excluding seasonal vaccinations including influenza and COVID-19. Participants were divided into 4 age categories based on natural breaks in the immunization schedule, 0 to 2 years, 3 to 7 years, 8 to 13 years and 14 to 17 years.

The demographics collected included: age, sex, admission and discharge diagnosis, past medical history, length of stay in hospital, length of stay on CTU, and the first 3 digits of the child’s postal code. Canadian postal codes indicate whether the address is urban or rural based on the second character, thus the first 3 digits of the postal code were used to determine if participants resided in an urban or rural area. Relevant data from the course of admission, including admission to intensive care, surgical interventions, or procedures was also recorded. Outcomes and other medical treatments during hospital stay were not recorded.

The Searching for Hardships and Obstacles to Shots (SHOTS) survey^17,18  was used to assess barriers to immunization and was completed by caregivers on paper or tablet. The SHOTS survey has been previously validated and found to be reliable in multiple studies with over 1000 total participants. The survey consists of a list of items describing common barriers for caregivers seeking immunizations for their child, divided into 3 subscales: access to shots, 12 items focused on issues that may impact ability to obtain a vaccine; concerns about shots, 6 items that may cause apprehension about vaccination; and, importance of shots, 5 items related to “timing, advice, beliefs about how important immunizations are to a child’s health.” For each stated barrier, respondents were asked to rate the degree to which each barrier is considered a problem for having their child vaccinated on a 5-point Likert scale, ranging from 0 (“not a problem”) to 4 (“very big problem”) (Supplemental Table 2). For each subscale, scores from each question were added up to determine a total for each subscale (range for access to shots subscale 0–48; range for concerns about shots subscale 0–24; range for importance of shots subscale 0–20). A total score for each respondent survey was determined by adding the subscale scores (range 0–92). To compare the subscales, each subscale was divided by the number of items making up the scale.

Translation services were provided to any non-English speaking families through either video call or voice translation services.

Ethics approval was obtained from the university research ethics board (study identification number: Pro00107899).

Descriptive analysis of baseline characteristics was undertaken, with continuous variables reported as median and interquartile range as the data were non-normally distributed. Categorical variables were reported as total and relative frequencies.

Children were determined to be up-to-date for each vaccine if they received the scheduled number of doses by the specified age for assessment, and up-to-date for all vaccines if they had received all doses of all scheduled vaccines by the specified age. The number and timing of doses was based on the provincial recommended immunization schedule.¹⁹  Previous iterations of the vaccination schedule were referenced according to the age of the child to ensure status was determined based on the relevant provincial immunization schedule at that time. The vaccine coverage for each vaccine among our hospitalized sample was compared with population-level data for the entire province using publicly available immunization data published by the provincial government for the 2021 year.²⁰  The provincial data are reported as percent coverage for each birth cohort by the ages of 1, 2, 7, 13, or 17 and does not include a composite, province wide, up to date status for comparison. For both our sample and the provincial data, a child was considered immunized if they had received their age-appropriate dose(s) by their birthday. For each vaccine dose of the study sample, 95% confidence intervals of proportions were determined. This was then compared with the corresponding value in the provincial data set and if the 95% confidence interval for the sample did not overlap with the coverage value for the population, it was considered to be a difference in coverage. When individual vaccine records were not accessible, either because of lack of electronic or paper record, because a public health unit was not identifiable or the public health unit did not reply to our request, these participants were excluded from the statistical analysis of vaccine coverage.

The SHOTS survey’s subscales and composite scores were characterized using the median and interquartile range. Given the non-normal distribution of scores, the Mann Whitney U test was employed to compare these scores based on vaccination status. The significance level was adjusted for the outcomes of the 3 subscales and composite score, with a P value below .0125 alpha deemed as significant.

We enrolled 250 children admitted to CTU between July 2021 and October 2022. Vaccination records were available for 244 of these patients (Fig 1). The median age was 3.33 years. Of patients, 47.5% enrolled were female, and the majority (81.6%) lived in urban settings. The median length of stay in hospital was 3 days. There was no statistical difference in age, sex, or length of stay in hospital or urban versus rural postal codes between the up-to-date and not up-to-date groups (Table 1). Forty-eight percent (n = 117) of participants fell between ages 0 to 2 years, 24.2% (n = 59) were 3 to 7 years, 16.8% (n = 41) were 8 to 13 years, and 11.1% (n = 27) were 14 to 17 years.

Comparing individual vaccine coverage rates of hospitalized children with 2021 age-based vaccine coverage reported by the province, our population of hospitalized children were more likely to be missing the first 3 doses of the DTaP-IPV-Hib series, the second dose of the MMR vaccine, the first dose of the meningococcal conjugate vaccine, all 3 doses of the pneumococcal conjugate vaccine, the first dose of the varicella vaccine, and the first dose of the hepatitis B (HBV) vaccine (Fig 2).

Only 142 (58.2%) of 244 children were up-to-date on all their immunizations. The children in the youngest and oldest age groups were less likely to be completely immunized (46.2% of 0 to 2 year olds and 55.6% of 14 to 17 year olds) compared with the children between 3 to 13 years of age. Vaccination rates by age group are depicted in Fig 3.

Of the 250 children enrolled, 236 caregivers completed the SHOTS survey assessing potential barriers to childhood vaccination. Of these 236, the immunization status was known for 230 children.

The composite SHOTS survey scores, encompassing all 3 subscales, showed that caregivers of children whose immunizations were not up-to-date reported significantly more barriers (median composite score 8.0, interquartile range [IQR] 3.0–20.0) to immunization compared with caregivers of children whose vaccines were up-to-date (median composite score 3.0, IQR 1.0–9.5) (P < .001) (Fig 4). The differences in median values were also found to be significantly different when responses were broken down into each of the 3 subscales. Caregivers whose children were under immunized scored a median of 0.2 on the access to shots subscale, 0.8 on the concerns about shots subscale, and 0.0 on the importance of shots subscale compared with medians of 0.1, 0.3, and 0.0 for caregivers of children whose immunizations are up-to-date.

This is the first study highlighting the disparity of immunization status between children admitted to hospital and those of the general population in a Canadian context. Of the 244 patients whom we were able to access immunization records, 102 (41.8%) were not up-to-date on all their recommended vaccinations. Although composite immunization rates are not published in our jurisdiction, we were able to compare coverage rates for individual vaccines at ages 2, 7, 13, and 17 years. This revealed that hospitalized patients were missing more doses of DTaP-IPV-Hib, MMR, meningococcal, pneumococcal, varicella, and HBV vaccines. Provincially our immunization rates do not meet national targets, but rates among hospitalized children are concerningly even lower.

To improve immunization uptake, the Canadian Pediatric Society has offered specific recommendations.²¹  Many of these focus on community-based programming, such as offering school-based immunization programs, which are applicable only to school aged children, and notifying caregivers when children are due for immunizations. However, minimal focus has been placed on the hospital setting as an opportunity to increase immunization uptake. Yet, the Government of Canada identifies admission to hospital as well as visits to outpatient clinics or emergency departments as valuable opportunities to offer vaccinations to patients of all ages. They note that this could be especially beneficial for those without regular access to health care as visits to acute care may be their only interactions with the healthcare system.²²  This opportunity is exemplified by a pilot program at Children’s Mercy Hospital (Kansas City, MO), which demonstrated an increase in vaccination status from 73% to 80% in hospitalized patients simply by screening immunization status of patients at admission and developing an immunization plan before discharge.²³  Shingler et al in 2011 identified reduced immunization rates in hospitalized children in New Zealand and immunized 83% of eligible children during admission, in addition to re-engaging all children with primary care providers.²⁴  A systematic review of hospital-based strategies for improving childhood immunization rates found that opportunistic vaccination programs are more effective than patient education, patient reminders, and establishment of community connections.²⁵  An assessment of both parental and healthcare provider perspectives on opportunistic vaccination in the United Kingdom has also shown this approach is acceptable for both groups.²⁶  These prior studies, together with our data showing low vaccination coverage rates in the hospitalized population, suggest an opportunistic immunization strategy in hospital could make a sizeable impact.

Jurisdictional and institutional variations in vaccination processes will certainly lead to nuanced differences in what will be needed for the development of an effective immunization strategy. However, we demonstrate that families of hospitalized children who are underimmunized cite difficulties with access as a more troublesome barrier than caregivers of children who are fully vaccinated. As has been demonstrated previously, opportunistic immunization programs during hospitalization remove the “access barrier” and are effective at improving immunization rates.^23–25,27 

Although opportunistic immunization in hospital could help eliminate the barrier of “access to vaccines” for some families, it is also important to acknowledge that barriers to immunization are multifactorial. We conducted the SHOTS survey to better understand the complexities of these barriers for families admitted to our hospital. Through this, we showed that in addition to access, families of hospitalized children who are underimmunized also cite concerns about, and perceived importance of, vaccines as a barriers. Previous qualitative studies of inpatients have also cited multiple levels of barriers to vaccination, including system-based, physician-level, parent-physician interactional, and parent-and child-level factors.²⁸  Further emphasizing the complexities of implementing in-hospital initiatives to improve immunization uptake, a review of accuracy of practitioner documentation of immunization status found that despite practitioners documenting 92% of children had received all age-appropriate vaccines, only 23% were truly up to date based on local guidelines.²⁹  Previous use of the SHOTS survey to evaluate changes in parental barriers to immunization over time found that perceived barriers to access decreased over time, suggesting that barriers to immunization are not static.³⁰  It is interesting to note that in this study³⁰  and 2 other published applications of the SHOTS survey, the mean composite scores reported by families were considerably higher than those reported by even our underimmunized families (Supplemental Table 3). These 3 other studies were conducted in the United States among different cultural groups and found mean composite scores ranging from 11.2 to 24.97.^30–32  Future qualitative research to better characterize the nature of parental concerns and understand the beliefs around importance of vaccination and how these change will help to develop multifaceted strategies of breaking down barriers to immunization.

Participant recruitment was limited by study team member availability. As a result, it is possible that specific communities and populations of patients were not included in our results. Notably, children admitted for short stays, children whose caregivers were unable to be in hospital, and children who were more acutely unwell were less likely to be seen by our research team. We also acknowledge the historical acts that have impacted our Indigenous community’s trust in the medical and scientific community and recognize that their voice may be underrepresented in this study through decisions to not participate. Further, the results of this study, and particularly the results of the caregiver survey, may have been impacted by the heightened public discourse around vaccine safety that was occurring during our data collection period because of the ongoing COVID-19 pandemic.

Our study determined that a cohort of hospitalized children were significantly underimmunized compared with national targets and compared with the immunization rates of their community. Caregivers of the underimmunized hospitalized children cite significantly more barriers to immunization when compared with hospitalized children who are up-to-date. Pursuing a hospital based immunization strategy could lead to improved immunization status for hospitalized children.

Thank you to the staff at the Stollery Children’s Hospital and University of Alberta who contributed to the conceptualization of this project including: Dr Samina Ali, Dr Troy Turner and Dr Bonita Lee; and Jesse Batara, biostatistician for The Women and Children’s Health Research Institute.