Association Between Human Papillomavirus Vaccination School-Entry Requirements and Vaccination Initiation

Key Points

Question

Are human papillomavirus vaccination requirements for school entry associated with vaccination initiation in select regions of the US?

Findings

In this cross-sectional study, 3 US jurisdictions with human papillomavirus immunization school-entry requirements in 2017 had higher levels of vaccination initiation than jurisdictions without such policies within the same region. Compared with nonpolicy jurisdictions in the same region, all policy jurisdictions except Virginia experienced greater differential changes in prepolicy and postpolicy vaccination initiation among girls and boys.

Meaning

The findings of this study suggest that human papillomavirus vaccination school-entry requirements are associated with increased vaccination initiation.

Abstract

Importance

Human papillomavirus (HPV) vaccination coverage is suboptimal in the US. The association between HPV vaccination requirements for school entry and HPV vaccination coverage remains to be studied.

Objective

To examine the association between HPV vaccination school-entry requirements and vaccination initiation in jurisdictions with such vaccination policies (ie, Virginia, the District of Columbia, and Rhode Island) compared with other regions of the US, as determined by the National Center for Chronic Disease Prevention and Health Promotion.

Design, Setting, and Participants

In a population-based, cross-sectional study, 2017 data from the National Immunization Survey–Teen database were used to determine HPV vaccination initiation. Data from 2008 to 2017 were then examined to assess the association between HPV vaccination school-entry policies and vaccination initiation. Data were obtained for adolescents aged 13 to 17 years in the US with health care professional–reported HPV vaccination histories (cross-sectional study, n = 4784; pre-post policy comparisons, n = 42 431). This study was conducted from May 1, 2019, to March 31, 2020.

Exposures

State-level HPV vaccination school-entry requirements from 2008 to 2017.

Main Outcomes and Measures

Health care professional–confirmed HPV vaccination initiation.

Results

The 2017 cross-sectional study included 4784 adolescents aged 13 to 17 years (2228 [46.6%] girls; 2556 [53.4%] boys; mean [SD] age, 15.0 [1.4] years; interquartile range, 14-16 years). Compared with nonpolicy jurisdictions within the same region, Rhode Island and the District of Columbia, which have HPV immunization school-entry requirements, had higher levels of HPV vaccination initiation (Rhode Island: adjusted odds ratio [aOR], 4.34; 95% CI, 2.16-10.00; District of Columbia: aOR, 2.35; 95% CI, 1.39-4.19). However, compared with regional nonpolicy states, Virginia’s HPV vaccination initiation did not differ significantly (aOR, 1.01; 95% CI, 0.72-1.42). The 2008-2017 pre-post policy comparisons involved 42 431 adolescents aged 13-17 years (22 362 [52.7%] girls; 20 069 [47.3%] boys; mean [SD] age, 15.0 [1.4] years; interquartile range, 14-16 years). Postpolicy levels of HPV vaccination initiation in girls was significantly higher in Rhode Island (aOR, 3.12; 95% CI, 1.92-5.07) than prepolicy values. Similar changes were noted for postpolicy HPV vaccination initiation in boys in the District of Columbia (aOR, 6.36; 95% CI, 4.27-9.46) and Rhode Island (aOR, 5.84; 95% CI, 3.92-8.69) compared with prepolicy measures. With respect to regional nonpolicy states during the same period, both girls and boys in Rhode Island and boys in the District of Columbia experienced larger increases in HPV vaccination initiation. For example, in Rhode Island, boys aged 16 to 17 years had 7.32 (95% CI, 3.56-15.06) times the change in pre-post policy HPV vaccination initiation, while girls aged 16 to 17 years had 1.28 (95% CI, 0.60-2.73) times the change. In the District of Columbia, boys had 6.36 (95% CI, 4.27-9.46) times the change in pre-post policy HPV vaccination initiation.

Conclusions and Relevance

The findings of this study suggest that HPV vaccination school-entry requirements are associated with increases in vaccination initiation. Expanding such policies may increase HPV vaccination in the US.

This cross-sectional study examines initiation of human papillomavirus vaccination in US jurisdictions with vs those without policies requiring vaccination for school entry.

Introduction

According to the Centers for Disease Control and Prevention, nearly all sexually active people will be infected with human papillomavirus (HPV) in their lifetime.¹ Approximately half of those infections will be high-risk HPV types that cause cancer.¹

The Centers for Disease Control and Prevention’s Advisory Committee of Immunization Practices recommends routine 2-dose HPV vaccination for children aged 11 to 12 years.² If administered prior to HPV exposure, the current 9-valent vaccine is nearly 100% effective in preventing infection from 9 HPV strains that cause most HPV-related cancers and genital warts.³

Despite the proven safety and efficacy of the HPV vaccine, its level of uptake has been lower compared with other recommended vaccines for adolescents. In response to modest HPV vaccination coverage, some parts of the US enacted school-entry requirements for HPV vaccination. As of 2019, Virginia, the District of Columbia, Rhode Island, and Puerto Rico have established such policies. Currently, Virginia’s policy includes only girls,⁴ while the District of Columbia and Rhode Island have sex-neutral requirements.^5,6,7 All policies allow for exemptions.^4,6,7,8 Data on HPV vaccination are available only for the first 3 jurisdictions; policies for those areas are included in the eTable in the Supplement.

Few studies assessed the association between HPV vaccination requirements for school entry and HPV vaccination coverage.^9,10,11,12 Our study, which aimed to address that gap, examined the association between school-entry HPV vaccination policies and vaccination initiation.

Methods

We used 2008-2017 National Immunization Survey (NIS)–Teen estimates of HPV vaccination initiation.¹³ In the NIS-Teen survey, parents/guardians of adolescents aged 13 to 17 years were contacted via random household telephone surveys to determine their adolescents’ vaccination status. After parental/guardian oral consent to collect the vaccination status was obtained, the adolescents’ health care professionals were mailed the Immunization History Questionnaire containing questions concerning adolescents’ vaccination histories and health care professionals’ practices.

The present study was conducted from May 1, 2019, to March 31, 2020. Our study used the publicly available 2008-2017 NIS-Teen data sets and was deemed exempt from review and informed patient consent by the policies of the University of California, Los Angeles, Institutional Review Board. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline for cross-sectional studies.

Our primary outcome was HPV vaccination initiation (≥1 HPV dose) as confirmed by health care professional questionnaires. To determine reference regions for the policy jurisdictions, we divided the US into regions according to those in the National Center for Chronic Disease Prevention and Health Promotion.¹⁴ Rhode Island was assigned to region I and Virginia and the District of Columbia were placed in region III. Results were stratified by age group. Since 13 years is the youngest age included in the survey and 15 years is the age after which the Centers for Disease Control and Prevention recommends 3 doses of HPV vaccines,² adolescents aged 13 to 15 years and those aged 16 to 17 years were analyzed separately.

Statistical Analysis

In the first analysis, we used the 2017 cross-sectional national data to calculate odds ratios (ORs) of HPV vaccination initiation coverage. Jurisdictions with HPV vaccination school-entry requirements were compared with those with no policies in the same region.

In the second analysis, we used the 2008-2017 database to calculate ORs and note any association between school-entry HPV vaccination requirements and vaccination initiation using prepolicy and postpolicy (pre-post) comparisons between Virginia, the District of Columbia, and Rhode Island. Virginia’s school-entry HPV vaccination requirement (for girls only) was implemented in October 2008.⁴ To be conservative and capture vaccination initiation data that reflected the policy change, 2009 was used as the start of the postpolicy period. The District of Columbia’s policies for girls were enacted in January 2009,⁵ and the policies for boys were enacted in the 2014-2015 academic school year.⁶ Thus, 2009 and 2015 served as the start of the postpolicy periods for girls and boys, respectively. Rhode Island’s sex-neutral policy was implemented in August 2015,⁷ so 2016 marked the beginning of the state’s postpolicy period. To test for significant temporal associations, we compared pre-post policy HPV vaccination initiation in jurisdictions that have policies with that in nonpolicy jurisdictions in the same region over the same time periods. Since the District of Columbia and Virginia share a reference region, each was omitted from the other’s analysis. As the prepolicy window in areas such as Virginia contained only a year of data, we modeled prepolicy time using an indicator depending on whether a data point occurred within the prepolicy window.

Human papillomavirus vaccination initiation was modeled based on sex (female and male), except for Virginia, as its policy applies only to girls, and age (13-15 and 16-17 years). Indicators for sex and age group were incorporated with interaction terms to test for differences. Prepolicy and postpolicy comparisons of vaccination initiation for female and male adolescents within each age group were conducted. Since HPV vaccination was not recommended for boys until 2011, data on male adolescents were not collected until that year.¹⁵

For both analyses, complete-case evaluation excluding adolescents with incomplete household surveys or inadequate health care professional information was conducted. Multivariable logistic regression analyses accounting for statistically and contextually significant sociodemographic variables (ie, sex, race/ethnicity, survey language, maternal educational level, health care professionals’ facility type, presence of a medical visit in the past year, and vaccine recommendation from health care professionals) were performed, weighted according to NIS-Teen Data User’s Guide Specifications.¹⁵ A 95% CI not including an OR of 1.00 or P < .05 was considered statistically significant. All statistical analyses were conducted using SAS, version 9.4 (SAS Institute Inc).

Results

Sample Population

For the 2017 cross-sectional analysis, 9906 parents/guardians of adolescents aged 13 to 17 years completed household interviews. The mean (SD) age of the study population was 15.0 (1.4) years (interquartile range, 14-16 years). We included 4784 adolescents (region I: n = 2074, region III: n = 2710) with adequate HPV vaccination information from health care professionals. A total of 2228 adolescents (46.6%) were girls (region I: n = 974, region III: n = 1254) and 2556 were boys (53.4%) (region I: n = 1100, region III: n = 1456). Vaccination was initiated in 1629 adolescents (78.5%) in region I and 1970 adolescents (72.7%) in region III.

For the 2008-2017 pre-post policy comparisons, 83 104 adolescents aged 13 to 17 years completed household interviews; 19 287 adolescents (23.2%) resided in policy jurisdictions and 63 817 adolescents (76.8%) resided in nonpolicy jurisdictions. We included 42 431 adolescents (policy jurisdictions: Virginia, n = 3361; District of Columbia, n = 3044; and Rhode Island, n = 3212; and nonpolicy regions I and III: n = 32 814) with adequate health care professional–reported HPV vaccination information. Of these adolescents, 22 362 were girls (52.7%) (policy jurisdictions: Virginia, n = 1736; District of Columbia, n = 1663; Rhode Island, n = 1676; and nonpolicy regions I and III: n = 17 287) and 20 069 were boys (47.3%) (policy jurisdictions: Virginia, n = 1625; District of Columbia, n = 1381; and Rhode Island, n = 1536; and nonpolicy regions I and III: n = 15 527). The mean (SD) age of the study population was 15.0 (1.4) years (interquartile range, 14-16 years). Human papillomavirus vaccination was initiated in 43.8% (n = 1473) of adolescents in Virginia, 58.6% (n = 1785) of those in the District of Columbia, 68.2% (n = 2192) of those in Rhode Island, and 51.4% (n = 16 872) of adolescents in nonpolicy regions I and III.

Unknown HPV vaccination status was not uncommon. Of 83 104 parents/guardians who were interviewed, 35 735 individuals (43.0%) were unable to determine the number of HPV vaccination injections their adolescent had received. This proportion was similar across regions, as approximately 45% of those in region I and 39% in region III were missing such data. Missing data on other variables of interest were sparse, except for the health care professionals’ facility type and status of HPV vaccination initiation recommendation. When vaccination data missingness was accounted for, less than 1% of the facility type and approximately 10% of health care professional recommendation data were missing. Owing to the modest proportions of missingness, we conducted a complete-case analysis.

Data Analysis

In cross-sectional analysis within regions I and III, 2017 HPV vaccination initiation in jurisdictions with HPV vaccination requirements for school entry were compared with those with no such policies (Table 1). Compared with region I nonpolicy states (ie, Connecticut, Maine, Massachusetts, New Hampshire, and Vermont), the overall adjusted OR (aOR) for HPV vaccination initiation in Rhode Island was 4.34 (95% CI, 2.16-10.00) (Table 1). Similarly, compared with region III nonpolicy states (ie, Delaware, Maryland, Pennsylvania, and West Virginia), the overall aOR for HPV vaccination initiation in the District of Columbia was 2.35 (95% CI, 1.39-4.19) (Table 2). In contrast, the overall aOR in Virginia (aOR, 1.01; 95% CI, 0.72-1.42) was not significantly different from the null value compared with region III nonpolicy states (Table 2). In the District of Columbia, the aOR of adolescents in whom HPV vaccination was initiated HPV was significantly higher (aOR, 2.45; 95% CI, 1.27-4.92) compared with that of Virginia (Table 2).

Table 1. Association Between HPV Vaccination School-Entry Requirement and 2017 HPV Vaccination Initiation in Region I.

Jurisdiction	Proportion of HPV initiation among adolescents aged 13-17 y, %	aOR (95% CI)a,b
Rhode Islandc	90.6
All other region I areas	78.1	4.34 (2.16-10.00)
Connecticut	71.2	5.57 (2.61-13.42)
Maine	76.4	4.00 (1.76-10.05)
Massachusetts	80.3	3.93 (1.83-9.49)
New Hampshire	72.4	4.23 (1.86-10.62)
Vermont	77.9	3.73 (1.72-9.07)

Abbreviations: aOR, adjusted odds ratio; HPV, human papillomavirus.

^aAdjusted for sex, race/ethnicity, survey language, maternal educational level, health care professional facility type, presence of a medical visit in the past year, and physician vaccine recommendation.

^bPolicy jurisdiction compared with nonpolicy jurisdiction with latter as reference group.

^cHPV vaccination required for school entry.

Table 2. Association Between HPV Vaccination School-Entry Requirement and 2017 HPV Vaccination Initiation in Region III.

Jurisdiction	Proportion of HPV initiation among adolescents aged 13-17 y, %	aOR (95% CI)a
		District of Columbia vs all other region III areas	Virginia vs all other region III areasb	District of Columbia vs Virginia
District of Columbiac	88.7	NA	NA	2.45 (1.27-4.92)
Virginiac	67.8	NA	NA
All other region III areas	72.4	2.35 (1.39-4.19)	1.01 (0.72-1.42)
Delaware	74.9	2.23 (1.19-4.34)	0.95 (0.59-1.53)
Maryland	70.6	2.31 (1.29-4.33)	1.00 (0.65-1.53)
Pennsylvania	73.9	2.14 (1.23-3.92)	0.91 (0.62-1.35)
West Virginia	58.9	3.40 (1.80-6.67)	1.37 (0.85-2.23)

Abbreviations: aOR, adjusted odds ratio; HPV, human papillomavirus; NA, not applicable.

^aAdjusted for sex, race/ethnicity, survey language, maternal educational level, health care professional facility type, presence of a medical visit in the past year, and physician vaccine recommendation.

^bPolicy jurisdiction compared with nonpolicy jurisdiction with the latter as reference group.

^cHPV vaccination required for school entry.

Virginia

Throughout the study period, Virginia had lower levels of vaccination initiation compared with nonpolicy states (Figure, A). After implementation of the HPV vaccination school-entry policy in Virginia, mean HPV vaccination initiation for girls aged 13 to 15 and 16 to 17 years increased from 39.6% to 51.9% and from 35.2% to 60.0%, respectively (Table 3). Pre-post policy vaccination changes in aOR were 0.86 (95% CI, 0.48-1.56) overall, 0.70 (95% CI, 0.34-1.44) for girls aged 13 to 15 years, and 1.41 (95% CI, 0.48-4.11) for girls aged 16 to 17 years times the change experienced by girls in nonpolicy region III states over the same time period (Table 4). While those associations were not statistically significant, we found significant increases in HPV vaccination initiation among the Virginia 16- to 17-year female age group, with an aOR 3.23 (95% CI, 1.17-8.90) times the aOR of vaccination initiation after policy implementation than their prepolicy peers. Although we were unable to compare pre-post policy vaccination initiation for boys in Virginia, the mean postpolicy vaccination initiation for those aged 13 to 15 and 16 to 17 years was 35.3% and 38.4%, respectively (Table 3).

Figure. Human Papillomavirus Vaccination Initiation for Policy and Control States by Sex: National Immunization Survey–Teen, 2008-2017.

A, Virginia enacted the policy for girls in October 2008. To be conservative, 2009 was used as the postpolicy marker for girls. B, The District of Columbia enacted policy for girls and boys in January 2009 and the 2014-2015 academic school year, respectively. To be conservative, 2009 and 2015 were used as the postpolicy marker for girls and boys, respectively. C, Rhode Island implemented policy for girls and boys in August 2015. To be conservative, 2016 was used as the postpolicy marker for both sexes.

Table 3. Prepolicy and Postpolicy HPV Vaccination Initiation in Male and Female Adolescents.

Jurisdiction	Girls, age, %				Boys, age, %
	13-15 y		16-17 y		13-15 y		16-17 y
	Prepolicy	Postpolicy	Prepolicy	Postpolicy	Prepolicy	Postpolicy	Prepolicy	Postpolicy
Virginia	39.6	51.9	35.2	60.0	NA	35.3	NA	38.4
Reference region	41.7	57.8	43.5	67.0	NA	42.5	NA	47.3
District of Columbia	33.0	67.2	41.7	74.5	37.6	76.7	47.2	85.6
Reference region	41.7	57.8	43.5	67.0	28.9	59.7	32.4	66.7
Rhode Island	68.6	90.9	80.8	86.5	57.6	87.0	61.7	92.3
Reference region	53.6	71.5	68.3	80.6	35.4	65.4	42.6	75.8

Abbreviations: HPV, human papillomavirus; NA, not applicable.

Table 4. Difference in Differences in Postpolicy vs Prepolicy HPV Initiation Between States With and Without Policies.

Jurisdiction	aOR (95% CI)a						P value, girl vs boy significancea
	Girls			Boysb
	Overall	13-15 y	16-17 y	Overall	13-15 y	16-17 y	Overall	13-15 y	16-17 y
Virginia	1.61 (0.93-2.80)	1.16 (0.60-2.24)	3.23 (1.17-8.90)	NA	NA	NA	NA	NA	NA
Reference region	1.87 (1.50-2.33)	1.65 (1.24-2.19)	2.29 (1.62-3.24)	NA	NA	NA	NA	NA	NA
Virginia vs reference region	0.86 (0.48-1.56)	0.70 (0.34-1.44)	1.41 (0.48-4.11)	NA	NA	NA	NA	NA	NA
District of Columbia	2.13 (1.31-3.45)	2.59 (1.37-4.89)	1.67 (0.78-3.58)	6.36 (4.27-9.46)	5.87 (3.61-9.55)	8.24 (4.00-16.96)	<.01	.04	<.01
Reference region	1.85 (1.47-2.31)	1.63 (1.22-2.17)	2.26 (1.59-3.22)	3.27 (2.81-3.80)	3.04 (2.51-3.68)	3.72 (2.91-4.75)	<.01	<.01	.02
District of Columbia vs reference region	1.15 (0.67-1.96)	1.59 (0.79-3.20)	0.74 (0.32-1.71)	1.94 (1.27-2.97)	1.94 (1.15-3.26)	2.22 (1.04-4.75)	.13	.66	.06
Rhode Island	3.12 (1.92-5.07)	5.92 (3.13-11.18)	1.28 (0.60-2.73)	5.84 (3.92-8.69)	5.23 (3.22-8.50)	7.32 (3.56-15.06)	.05	.76	<.01
Reference region	1.55 (1.24-1.94)	1.65 (1.23-2.21)	1.44 (1.01-2.05)	2.82 (2.43-3.28)	2.77 (2.29-3.35)	2.98 (2.33-3.80)	<.01	<.01	<.01
Rhode Island vs reference region	2.01 (1.18-3.43)	3.59 (1.78-7.21)	0.89 (0.38-2.05)	2.07 (1.35-3.16)	1.89 (1.12-3.18)	2.46 (1.15-5.26)	.94	.15	.08

Abbreviations: aOR, adjusted odds ratio; NA, not applicable.

^aAdjusted for sex, race/ethnicity, survey language, maternal educational level, health care professional facility type, presence of a medical visit in the past year, and physician vaccine recommendation.

^bPrepolicy vaccination initiation data not available for boys in Virginia.

District of Columbia

In the District of Columbia, the level of HPV vaccination initiation among girls was higher than that in its nonpolicy peers, with such measures among boys reaching similar levels during the postpolicy period (Figure, B). Mean postpolicy HPV vaccination initiation increased from 33.0% to 67.2% for girls aged 13 to 15 years and from 41.7% to 74.5% for those aged 16 to 17 years (Table 3). Pre-post policy vaccination change was 1.15 (95% CI, 0.67-1.96) overall, 1.59 (95% CI, 0.79-3.20) for girls aged 13 to 15 years, and 0.74 (95% CI, 0.32-1.71) for girls aged 16 to 17 years times the change experienced by girls in nonpolicy region III states over the same time period (Table 4). Vaccination initiation over the prepolicy and postpolicy period increased overall (aOR, 2.13; 95% CI, 1.31-3.45) and in girls aged 13 to 15 years (aOR, 2.59; 95% CI, 1.37-4.89) in the District of Columbia (Table 4).

For boys aged 13 to 15 years, mean postpolicy HPV vaccination initiation rates increased from 37.6% to 76.7%; in those aged 16 to 17 years, initiation rates increased from 47.2% to 85.6% (Table 3). Overall postpolicy HPV vaccination initiation for boys in the District of Columbia was 6.36 (95% CI 4.27-9.46) times that of the prepolicy time period (Table 4). The pre-post policy HPV vaccination initiation changes for boys overall (aOR, 1.94; 95% CI, 1.27-2.97), those aged 13 to 15 years (aOR, 1.94; 95% CI, 1.15-3.26), and boys aged 16 to 17 years (aOR, 2.22; 95% CI, 1.04-4.75) were significantly greater than changes for boys in other region III states over the same time period (Table 4).

The District of Columbia and other region III jurisdictions had a significantly greater increase in the odds of HPV vaccination initiation of boys compared with girls across all age groups. For example, in the District of Columbia, boys had 6.36 (95% CI, 4.27-9.46) times the change in pre-post policy HPV vaccination initiation, while girls had 2.13 (95% CI, 1.31-3.45) times the change, suggesting that the District of Columbia had a significantly greater increase in pre-post policy HPV vaccination initiation of boys compared with girls (P < .01) (Table 4). Since there were no statistically significant differences when comparing the sex variations between the District of Columbia and the other region III jurisdictions, the differential change in vaccination initiation between girls and boys was similar between the District of Columbia and the rest of region III (Table 4).

Rhode Island

The level of initiation of HPV vaccination among girls in Rhode Island was higher than that of its nonpolicy counterparts, with such measures among male adolescents surpassing those of their female peers during the postpolicy period (Figure, C). After the introduction of HPV vaccination school-entry policy in Rhode Island, mean vaccination initiation for girls aged 13 to 15 and 16 to 17 years increased from 68.6% to 90.9% and from 80.8% to 86.5%, respectively (Table 3). Overall pre-post policy initiation change in girls (aOR, 2.01; 95% CI, 1.18-3.43) and in girls aged 13 to 15 years (aOR, 3.59; 95% CI, 1.78-7.21) was significantly higher compared with other region I jurisdictions during the same time period (Table 4). However, levels of vaccination in girls aged 16 to 17 years in Rhode Island (aOR, 0.89; 95% CI, 0.38-2.05) did not experience significant pre-post policy changes compared with girls in region I during the same time period (Table 4).

For boys aged 13 to 15 and 16 to 17 years, mean postpolicy HPV vaccination initiation increased from 57.6% to 87.0% and from 61.7% to 92.3%, respectively (Table 3). Overall postpolicy HPV vaccination initiation for boys in Rhode Island was 5.84 (95% CI, 3.92-8.69) times that of prepolicy measures. Pre-post policy HPV vaccination initiation change in boys was overall significantly higher (aOR, 2.07; 95% CI, 1.35-3.16) compared with other region I jurisdictions (Table 4). Younger boys (age, 13-15 years) had 1.89 (95% CI, 1.12-3.18) and older boys (age, 16-17 years) in Rhode Island had 2.46 (95% CI, 1.15-5.26) times the change in HPV vaccination initiation compared with their peers in region I over the same time period (Table 4).

We found the increase in odds of HPV vaccination initiation in boys in Rhode Island and other region I jurisdictions to be significantly larger than that for girls across all age groups except for boys aged 13 to 15 years. For example, in Rhode Island, boys aged 16 to 17 years had 7.32 (95% CI, 3.56-15.06) times the change in pre-post policy HPV vaccination initiation, while girls aged 16 to 17 years had 1.28 (95% CI, 0.60-2.73) times the change, suggesting that Rhode Island had a significantly greater increase in pre-post policy HPV vaccination initiation of boys aged 16 to 17 years compared with such girls (P < .01) (Table 4). There were no statistically significant differences when comparing the sex variations between Rhode Island and other region I jurisdictions. Thus, the differential change in vaccination initiation between girls and boys was similar between Rhode Island and the rest of region I (Table 4).

Discussion

Using 2017 NIS-Teen data, we conducted a cross-sectional analysis comparing the jurisdictions with HPV vaccination school-entry requirements with those with no policies in the same region. We also compared postpolicy HPV vaccination initiation with prepolicy values between policy jurisdictions and nonpolicy regional jurisdictions over the same time period.

The findings suggest that policy jurisdictions had higher HPV vaccination initiation levels compared with nonpolicy states within the same region. Furthermore, compared with nonpolicy states in the same region, greater differential changes in female and male pre-post policy vaccination initiation were noted in all policy jurisdictions except Virginia.

Compared with Virginia and the District of Columbia, Rhode Island has the most sex-inclusive and restrictive HPV vaccination school-entry policy. Girls and boys must receive the first dose of HPV vaccine before entering seventh grade and complete the series before entering ninth grade.⁷ Parents and guardians seeking immunization exemptions for their children can opt out for medical or religious reasons.⁷ In 2017, the state’s school-entry policy was associated with higher HPV vaccination initiation levels for adolescents aged 13 to 17 years compared with nonpolicy neighboring states.

To analyze the policy’s sex-specific associations, Thompson et al¹⁰ conducted a difference-in-differences comparison for Rhode Island’s policy that used a multistate control group. That study suggested a postpolicy increase in HPV vaccination initiation among boys but no such change for girls. In contrast, compared with nonpolicy regional states, our study showed an apparent increased postpolicy HPV vaccination initiation for both sexes in their respective age groups, except for girls aged 16 to 17 years. The nonsignificant change in older girls’ postpolicy HPV vaccination initiation might be associated with their high prepolicy coverage.

Compared with the rest of region I during the same time period, Rhode Island had a similar differential change in pre-post policy HPV vaccination initiation between girls and boys. Such nonsignificant changes might be due to insufficient statistical power because we only had 2 years of postpolicy data (ie, 2016-2017) available for analysis.

In 2009, the District of Columbia required girls to receive at least 1 dose of HPV vaccine before entering sixth grade⁵; in 2014, the jurisdiction expanded its immunization policy to include boys and all students entering seventh to twelfth grades.⁶ According to Perkins et al’s¹¹ analysis of the 2009-2013 NIS-Teen database, the District of Columbia’s HPV vaccination school-entry policy was not associated with higher levels of HPV vaccination compared with nonpolicy jurisdictions.

Our study findings, which took into account the District of Columbia’s 2014 policy changes, suggest that the sex- and age-inclusive policy was associated with increased rates of HPV vaccination. In 2017, the level of HPV vaccination was higher in the District of Columbia compared with that in nonpolicy states. In addition, the District of Columbia had higher levels of HPV vaccination compared with Virginia, suggesting that the former’s more inclusive and stricter policy (ie, annual exemption filing requirements)^5,6,8 was associated with greater increases in vaccination initiation than the latter. Furthermore, the jurisdiction’s school-entry policy appeared to increase postpolicy HPV vaccination initiation among boys and younger girls. Like Rhode Island, the District of Columbia’s requirement had similar differential change in HPV vaccination initiation between girls and boys compared with nonpolicy region III states during the same time period.

Virginia’s HPV vaccination school-entry policy requires that girls receive 3 doses of the HPV vaccine series, with the first dose administered before sixth grade.⁴ Previous studies suggested that the state’s requirement was not associated with increased HPV vaccination among the target age group.^9,11,12 Explanations included Virginia’s lenient regulations (eg, no required documentation for vaccination exemption)⁴ and weak vaccine recommendations by physicians.^9,11,12

Our study suggests that Virginia’s female-specific and less-restrictive HPV vaccination requirement for school entry did not result in higher levels of 2017 vaccination initiation compared with nonpolicy jurisdictions. The differential change in Virginia’s female HPV vaccination initiation over the pre-post policy period was similar to that of nonpolicy region III states. Nonsignificant changes in postpolicy vaccination initiation might be due to insufficient statistical power because we had only 1 year of prepolicy data (ie, 2008) available for analysis.

One finding of our study concerned the association between physician recommendation of HPV vaccination and vaccination initiation. Previous studies explored the importance of physicians’ roles in increasing HPV vaccine uptake.^16,17,18 After accounting for that variable, our results suggested that school-entry HPV immunization prerequisites were influential in increasing vaccination initiation, independent of health care professional vaccine recommendation.

Limitations

Our study has several limitations. Given the scarce data available for prepolicy HPV vaccination initiation for Virginia and the District of Columbia, along with postpolicy vaccination data for Rhode Island, we had insufficient statistical power in some analyses. That lack of power might have led to uncertainty in our results, as indicated by the large 95% CIs. Despite that limitation, pre-post policy comparisons for policy jurisdictions generally suggested increasing levels for vaccination initiation. We also excluded a sizable portion of adolescents with inadequate data on HPV vaccination reported by health care professionals, thereby reducing the generalizability of our results.

Conclusions

The findings of the study suggest that sex-neutral, restrictive HPV vaccination requirements for school entry are associated with increased vaccination initiation among adolescents aged 13 to 17 years. The strength and consistency of our findings suggest that HPV vaccination should be included in school-entry requirements.

Supplement.

eTable. Human Papillomavirus Vaccination School-Entry Requirements by State