Abstract
Objectives:
Before the 2017-2018 school year, Pennsylvania shortened the grace period for provisional entrants—kindergarteners who are not up-to-date on vaccination and do not have medical or nonmedical exemption—from 8 months to 5 days. We analyzed the impact of this change on school-entry vaccination status.
Methods:
Using data from the Pennsylvania Department of Health for school years 2015-2016 through 2018-2019, we examined state-level trends in Pennsylvania kindergarteners’ vaccination status, including the percentage who were up-to-date on each required vaccine, provisionally enrolled, medically exempted from vaccination, and nonmedically exempted from vaccination. Using the Spearman correlation coefficient, we assessed associations at the school level among changes in kindergarteners’ vaccination status after the grace period was shortened.
Results:
From 2016-2017 to 2017-2018, the provisional entrance rate of kindergarteners in Pennsylvania decreased substantially after the change in the grace period (from 8.1% to 2.2%), the medical exemption rate remained stable, and the nonmedical exemption rate increased slightly (from 1.8% to 2.5%). The percentage of kindergarteners up-to-date on required vaccines increased or remained stable across the study period except for polio, which decreased from 97.9% in 2015-2016 to 96.2% in 2018-2019. The change in provisional entrance rate was negatively associated with change in kindergarteners up-to-date on required vaccines (ρ range, −0.30 to −0.70) but not with change in medical or nonmedical exemptions (ρ range, −0.01 to −0.08).
Conclusions:
Efforts to reduce provisional entrants may increase the percentage of kindergarteners up-to-date on vaccinations at school entry without a corresponding increase in exemptions.
US-based research on childhood vaccination has largely focused on vaccine hesitancy and the use of nonmedical exemptions from school-entry requirements by parents having personal, philosophical, or religious objections to vaccinating their children.1,2 However, nonmedical exemption is only one of numerous pathways for children who are not up-to-date on vaccination to enter school. Other pathways include a medical exemption for children with a contraindication to vaccination or provisional entrance (also called conditional entrance in some states), which can be summarized as a temporary admission for a child who has received some vaccinations but is not up-to-date on all required vaccinations and does not have an exemption. 3
While recent efforts to increase the number of children entering school fully up-to-date on required vaccinations have largely focused on reducing the use of nonmedical exemptions, the percentage of students admitted provisionally (2.0%) was only slightly less than the percentage with an exemption (2.2%), and in the 2020-2021 school year, half of the 28 states that reported data had more provisional entrants than students with an exemption. 4 Because no national-level vaccination requirements exist for children entering school, each state (and Washington, DC) is responsible for developing, administering, and implementing its own set of regulations, which include the requirements for being considered up-to-date, exempted, provisionally enrolled, or out of compliance. 5 Provisional enrollment is generally reserved for children who have started but not completed a multiple-dose vaccine series, and it provides additional time for those students to meet the requirements. Variation among state provisional regulations includes who is eligible, the length of the grace period for a student to become up-to-date, and the severity of the penalty for not meeting the criteria.
Despite the sizable contribution that provisional entrants make to undervaccination in US schools, few studies have examined this group of children. To our knowledge, no evidence links provisional entrance with vaccine hesitancy, which is important because it suggests that alternate conditions lead to children being provisionally enrolled. To that point, initial studies have demonstrated that efforts to reduce provisional entrants led to an increase in vaccination coverage without corresponding increases in exemptions.6,7 These findings suggest that parents of students who end up provisionally enrolled face some other barrier (aside from vaccine hesitancy) to ensuring that their children meet the school entry vaccination requirements. However, this group of children remains largely overlooked in efforts to increase vaccination rates among schoolchildren.
One effort to reduce provisional entrants occurred in Pennsylvania. Prior to the 2017-2018 school year, the Pennsylvania Department of Health (PDOH) reduced the grace period from 8 months to 5 days after the first day of school for provisional entrants to become up-to-date or to file a catch-up plan. 8 This change was designed to discourage provisional entrance and to bolster the number of students who were fully up-to-date on required vaccinations upon entering kindergarten. 9 Initial state-level analysis showed that this regulatory change was successful in that the percentage of provisional entrants decreased statewide in the first year after the change. 7 We examined changes in the first 2 years after the grace period was shortened and evaluated the association between school-level changes in provisional entrance rates and changes in exemption and up-to-date rates.
Methods
Pennsylvania’s immunization requirements are detailed in the Health and Safety section of the Pennsylvania Code (28 Pa Code §23). 10 Required vaccinations for kindergarteners in Pennsylvania include DTaP (diphtheria, tetanus, and pertussis), MMR (measles, mumps, and rubella), polio, hepatitis B, and varicella. Children can get an exemption to ≥1 vaccine for medical reasons (requires a written statement from a physician) or nonmedical reasons (requires a written statement from a parent or guardian objecting to immunization on religious grounds or based on strong ethical or moral convictions). Provisional admission can be granted to a child who has started but not completed a multiple-dose vaccine series on the first day of school. If the student is overdue to receive a final dose, the student must do so within 5 days. If the student is missing multiple doses, the student must receive the next dose and submit a schedule for the additional doses within 5 days. If the next dose of the vaccine is not medically appropriate to receive within the 5-day period from the first day of school, it must be received within 5 days of when it is medically appropriate. Children who are not up-to-date, do not have an exemption, do not qualify for provisional entrance, or do not meet the stipulations of provisional entrance once granted may be excluded from school. Schools and school administrators are responsible for assessing the immunization status of the children and enforcing the regulations, while PDOH is responsible for monitoring schools’ compliance.
We obtained annual state-level kindergarten immunization summary reports from PDOH for the school years 2015-2016 through 2018-2019. 11 Upon request to PDOH, we also gathered school-level immunization data for all schools with >20 enrolled kindergarteners, which were available from 2015-2016 through 2018-2019 (the data are censored by PDOH to protect the confidentiality of students in small schools). Because the data were publicly available and deidentified, institutional board review was not required, and institutional review board approval was not sought.
The state- and school-level data included counts of children who were enrolled; who were up-to-date on each required vaccine; and who had a provisional entrance, medical exemption, or nonmedical exemption (separated into religious and philosophical exemptions). The up-to-date information for each vaccine is considered independently of the other vaccines; for example, a child may be counted as up-to-date on the MMR vaccine but not the varicella vaccine (if the child has an exemption for that vaccine). A child is counted as having an exemption (medical, religious, or philosophical) if the child has an exemption for any of the required vaccines. As such, a child with an exemption for 1 vaccine may still be included in the up-to-date counts of the vaccines for which the child does not have an exemption. Provisional entrants are counted similarly to exempted students; a student may be a provisional entrant (because the student requires a final dose of 1 vaccine) and be counted as up-to-date on some vaccines. The yearly reporting window 12 for schools to submit the immunization status of their students is December 1-31; thus, the data reflect the status of students immediately preceding or during that period.
For temporal stability in the school-level analysis, we pooled enrollment and immunization data for each school from the 2 years prior to the change (2015-2016 and 2016-2017) and the 2 years after it (2017-2018 and 2018-2019). We calculated the school-level percentage-point change between the periods in kindergarteners up-to-date on each of the required vaccines, provisional entrants, medical exemptions, and nonmedical exemptions. We used the Spearman correlation coefficient to test whether changes in provisional entrance were associated with changes in exemptions and students up-to-date on each required vaccine. We used R version 4.0 (R Core Team) for all data processing and analyses.
Results
Statewide, the provisional entrance rate was 5.1% in 2015-2016 and 8.1% in 2016-2017, the year before the regulation change. After the change, the provisional entrance rate decreased to 2.2% in 2017-2018 before increasing slightly to 2.6% in 2018-2019. Medical exemptions remained stable during the 4-year period, with a high of 0.5% in 2017-2018. Nonmedical exemptions increased gradually from 1.8% in 2015-2016 to 2.5% in 2018-2019; religious exemptions increased by 0.4%, while philosophical exemptions increased by 0.3%.
The percentage of kindergarteners up-to-date on the polio vaccine decreased from 97.9% in 2015-2016 to 96.2% in 2018-2019. For hepatitis B, the percentage up-to-date was stable across the school years at 97.0%. The percentage of kindergarteners up-to-date on DTaP, MMR, and varicella vaccination in 2016-2017 (prior to the grace period) was 94.8%, 93.7%, and 94.7%, respectively. In the year that the grace period was shortened, the percentage of kindergarteners up-to-date on these 3 vaccines increased by about 1.5 percentage points and remained at this level in 2018-2019.
Despite the censoring of data from schools with <20 kindergarteners each year, school-level data included the immunization status of at least 91.0% (in 2015-2016) of all kindergarteners each year, with a high of 94.2% (in 2018-2019) (Table 1).
Summary statistics for school-level vaccination data, Pennsylvania, 2015-2016 through 2018-2019 a
Data include the number of schools with ≥20 kindergarteners included each year, the total number of kindergarteners represented in the data, and the percentage of all kindergarteners represented (based on all reported data). Data source: Pennsylvania Department of Health. 11
The median school-level provisional entrance rate dropped by nearly 4 percentage points after the change (from 4.5% [IQR, 1.9%-8.2%] during 2015-2017 to 0.8% [IQR, 0%-2.0%] during 2017-2019) (Table 2). For religious and philosophical exemptions, the median rates (0.6 and 0.3 percentage-point changes, respectively) and upper bound of the IQR (0.5 and 0.2 percentage-point changes) increased slightly. For the percentage of students up-to-date on required vaccines, the median and lower and upper IQR bounds increased for DTaP (0.7, 1.8, and 1.3 percentage-point changes, respectively), MMR (1.6, 2.9, and 0.9 percentage-point changes, respectively), and varicella (1.7, 3.1, and 1.0 percentage-point changes, respectively) after the regulatory change. For hepatitis B, the values were similar before and after the change, while the percentage of students up-to-date on the polio vaccine fell (−1.1, −1.5, −0.8 percentage-point changes in the median and lower and upper IQR bounds, respectively).
Percentage of kindergarteners who had provisional entrance and an exemption (religious, philosophical, or medical) and were up-to-date on required vaccinations before (2015-2016 and 2016-2017) and after (2017-2018 and 2018-2019) a regulation change shortening the grace period of provisional entrance, Pennsylvania a
Data source: School-level immunization data for all schools with >20 enrolled kindergarteners, which were gathered from the Pennsylvania Department of Health upon request.
Provisional entrants are children who have started but not completed a multiple-dose vaccine series for ≥1 required vaccine and do not have an exemption from vaccination.
Maps of provisional entrance rates highlight the difference in the magnitude before and after the grace period was shortened (Figure 1). Because schools cannot be meaningfully mapped at a state level, the school-level data were aggregated to 10-km hexagon-shaped spatial units for visualization. After the grace period was shortened, 75.7% of schools reported a decrease in provisional entrance rates; however, the magnitude of the decreases was geographically heterogeneous. When mapped with the hexagons, the areas with the most extreme changes (a decrease of ≥23.2 percentage points and an increase of ≥1 percentage point) appear to be geographically distributed across the state and not concentrated in a single region (Figure 1).
Percentage of provisional entrants of kindergarteners in (A) 2015-2016 and 2016-2017 pooled data (before the change in the provisional entrant grace period) and (B) 2017-2018 and 2018-2019 pooled data (after the change), Pennsylvania. (C) Change in the percentage of provisional entrants between the 2 periods. In the maps, school-level data are aggregated to 10-km hexagons for display purposes. Provisional entrants are children who have started but not completed a multiple-dose vaccine series for ≥1 required vaccine and do not have an exemption from vaccination. Data source: School-level immunization data for all schools with >20 enrolled kindergarteners, which were gathered from the Pennsylvania Department of Health upon request.
We observed negative associations among changes in provisional entrants and students up-to-date for the required vaccines; in particular, the associations for DTaP (ρ = −0.56), MMR (R = −0.69), and varicella (ρ = −0.70) were strong, signaling that provisional entrants prior to the regulation change were likely not up-to-date on ≥1 of these 3 vaccines (Figure 2). The correlation coefficients were smaller in magnitude (but still negative) for change in percentage up-to-date on polio (ρ = −0.30) and hepatitis B (ρ = −0.37) and change in provisional entrants (ρ = −0.01). We also observed that changes in the provisional entrance rates were not strongly correlated with changes in medical exemption rates (ρ = −0.01), religious exemption rates (ρ = −0.01), or philosophical exemption rates (ρ = −0.08) (Figure 2).
Spearman correlation coefficients for school-level changes after the change in the provisional entrant grace period (2015-2016 and 2016-2017 pooled to 2017-2018 and 2018-2019 pooled) for percentage of kindergarteners who are provisional entrants, have exemptions, and are up-to-date on required vaccinations in Pennsylvania. Provisional entrants are children who have started but not completed a multiple-dose vaccine series for ≥1 required vaccines and do not have an exemption from vaccination. Data source: School-level immunization data for all schools with >20 enrolled kindergarteners, which were gathered from the Pennsylvania Department of Health upon request.
Discussion
In Pennsylvania, after the grace period was shortened from 8 months to 5 days for provisional entrants to become up-to-date on vaccines or file a plan, the percentage of incoming kindergarteners with provisional entrance decreased in the first year and stayed at this lower level in the second year. The large decrease in percentage of provisional entrants and increases in the percentage of kindergarteners up-to-date on 3 of 5 vaccines suggest that the regulatory change was successful.
One potential concern when modifying school entry vaccination or exemption requirements is the chance of a replacement effect wherein parents choose a different pathway to enroll a child who is not up-to-date. 6 In a state such as Pennsylvania, which has an undemanding process for claiming a nonmedical exemption, a more restrictive approach to provisional entrants may have prompted parents who were not vaccine hesitant to claim a nonmedical exemption instead of making sure that their children became fully up-to-date. These nonmedical exemptions for “convenience” rather than “conviction” have been observed in other states. 13 We did not observe evidence of a replacement effect in Pennsylvania, suggesting that the more restrictive stance on provisional entrants did not prompt parents to seek medical or nonmedical exemptions as an alternative to provisional entrance. While medical and nonmedical exemptions both increased slightly after the change, the increases did not appear to deviate from trends established prior to the change in the provisional grace period, and the magnitude of the increases was small as compared with the corresponding decrease in provisional entrants. The school-level correlation analysis corroborated these findings: we did not observe a relationship between change in provisional entrants and change in kindergarteners with nonmedical or medical exemptions.
In Pennsylvania, an immediate reduction in the percentage of kindergarteners with provisional entrance and an increase in the percentage up-to-date on 3 vaccines followed the shortening of the grace period; furthermore, the changes established in the first year were sustained in the second year after the change. However, the overall impacts of changes in laws or regulations may not be fully realized until several years later, as shown recently in California and Michigan.6,14 Parents may simply need time to adjust to the new or updated vaccine requirements, especially those who may be vaccine hesitant and are looking for a means to avoid vaccinating their children. Thus, further monitoring of the vaccination status of Pennsylvania students is warranted not only to ensure that uptake remains high but also to better understand the long-term effects of the regulation change.
Although provisional entrance rates decreased in most schools and regions after the grace period was shortened, the magnitude of change varied geographically throughout the state. Because provisional entrants require schools to monitor and follow up with these students, the ability to administer the 5-day requirement may be resource dependent. 7 Understanding how school or neighborhood characteristics relate to changes in provisional entrance rates after shortening the grace period may uncover additional information for states considering similar initiatives; notably, some schools may require additional resources to implement a more restrictive approach (eg, shortening the grace period) for provisional entrants, especially those with consistently high rates of provisional entrance.
The analysis of kindergarteners up-to-date on each required vaccine showed that polio and hepatitis B vaccination rates remained relatively high and stable throughout the study period. Given the changes in provisional entrance rates, this finding suggests that provisional entrants prior to the regulatory change were provisional because they were not up-to-date on DTaP, MMR, and/or varicella. Understanding the reasons that some children are up-to-date on some but not all required vaccines at school entry provides an avenue for further research that may assist policy makers and school administrators in developing effective interventions (eg, modifying the regulations pertaining to provisional entrants or reminding parents of incoming kindergarteners which required vaccines are most often overlooked prior to the start of school). Moreover, these findings highlight the importance of considering factors other than vaccine hesitancy, such as barriers to vaccination, when attempting to increase vaccine coverage among children entering school.
Limitations
This study had several limitations. First, the findings were based on the number of students who remained provisionally enrolled in December (when reporting occurred). As such, we could not determine whether the findings resulted from (1) fewer students entering school provisionally at the beginning of the school year or (2) a similar number of students entering school provisionally at the beginning of the school year but fewer students remaining provisionally enrolled until December (ie, more provisional entrants got up-to-date on vaccination from the first day of school until the reporting period). Second, because our data were cross-sectional, we cannot be certain that the change in the grace period for provisional entrants prompted the observed changes. However, we are optimistic that the regulation change was responsible, because no other changes in vaccine or exemption requirements were made during this period.
Conclusions
While recent changes in vaccine policies and regulations have largely targeted nonmedical exemptions, efforts focusing on provisional entrants provide an alternate approach to increase the number of students entering school up-to-date on vaccination. Furthermore, measures targeting provisional entrance are unlikely to be accompanied by the high-profile pushback associated with efforts to remove or restrict nonmedical or medical exemptions.15-20 In Pennsylvania, the regulatory change shortening the grace period for provisional entrants was followed by a decrease in the provisional entrance rate for kindergarteners. Because there was no corresponding increase in the rate of exemptions after this change, the net result was an increase in the percentage of kindergarteners up-to-date on required vaccinations. Our work highlights outcomes associated with this regulatory change in Pennsylvania and can inform other states considering similar efforts to increase vaccination coverage. Future research is warranted to illuminate why students require provisional entrance when they should be up-to-date prior to attending school. Future research on the impact that provisional entrants have on infectious disease outbreak risk would provide additional information about the importance of addressing this overlooked pathway for children who are not up-to-date on vaccination to enter school.
Footnotes
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was supported in part by a research grant from the Investigator-Initiated Studies Program of Merck Sharp & Dohme Corp (MISP 59241). The opinions expressed in this article are those of the authors and do not necessarily represent those of Merck Sharp & Dohme Corp. The funders had no role in the study design; data collection, analysis, and interpretation; preparation of the article; or decision to publish.
