Pharmacy care has emerged as an increasingly important component of the healthcare landscape. Pharmacies perform a front-line role in public health by providing services such as medicine dispensing, patient consultation, preventative screenings, disease management, vaccine delivery, and diagnostic testing. These services reflect a continued shift from “product-centered” to “patient-centered” pharmacy care, where holistic and consultive services are becoming increasingly emphasized [1,2]. Recently, pharmacies have been instrumental in supporting the United States’ response and recovery throughout the COVID-19 pandemic [3]. Pharmacies are well-suited to provide preventive healthcare services due to their convenient locations, increased operational hours, and improved flexibility [4,5]. They also play a crucial role in ensuring equitable access to healthcare by reaching underserved individuals who lack access to other healthcare settings [5], as well as rural residents who are less frequently served by primary care providers [6]. However, recent restructuring in the pharmacy industry has created a significant trend of retail pharmacy closures across the United States, creating gaps in spatial accessibility with adverse impacts on rural and marginalized communities [7–11].

Despite the important and expanded front-line role that pharmacies play in public health, their spatial and temporal accessibility remains understudied [12]. Most existing studies treat pharmacy locations as homogenous, residential areas as centroids, and calculate distances as straight lines [12]. Spatial or geographic accessibility of healthcare services is increasingly recognized alongside other accessibility factors, such as affordability, availability, and acceptability, and measured using geographic information systems (GIS). Research indicates that geographic access impacts the utilization of healthcare services, including primary care [13] and hospitals [14], and that longer travel times to pharmacies are associated with lower utilization rates [15]. Despite this evidence, the literature on geographic access to pharmacies is limited and existing studies rely on density or distance measures that do not account for distance decay or spatial interaction between locations of supply and demand [12].

We address this gap in the literature by applying the Enhanced Two-Step Floating Catchment Area (E2SFCA) method [16] at one-hour intervals for typical weekdays and weekends for Vermont pharmacies. Two-step floating catchment (2SFCA) approaches to measuring spatial accessibility are widely used and improve upon simpler methods by modeling spatial interactions, measuring accessibility for a residential area of demand as the sum of service-to-population ratios for catchment areas around service locations [17,18]. The “enhanced” form (E2SFCA) also accounts for distance decay, modeling the decreasing likelihood of interaction between more distant locations [16].

To our knowledge, only four other studies have applied the 2SFCA [19–21] or E2SFCA [22] method to pharmacy access, and none of these considered how accessibility varies by time. Our study contributes to this literature by measuring varying levels of service at retail pharmacy locations and by adding a temporal dimension to accessibility. The limited use of floating catchment methods for studies of pharmacy access may be rooted in the lack of data on service levels and locations. All four floating catchment studies cited above treated pharmacies as equivalent in terms of levels of service or supply, whereas the floating catchment method requires a measure of service at each location. We address these limitations by surveying each pharmacy location in Vermont for their staffing levels and typical hours of operation. This unique combination of data allows us to ask three novel questions about spatio-temporal patterns of pharmacy access at underserved places and times in Vermont.

First, does spatial accessibility to pharmacies vary between metropolitan, micropolitan, and rural towns in Vermont during conventional business hours? Rural populations across the United States generally have more limited geographic access to pharmacies, with a smaller proportion of rural census tracts having access to at least one pharmacy per 10,000 people compared with suburban and urban tracts [21,23]. Additionally, rural populations disproportionately rely on a single “keystone” pharmacy for access and may be more severely impacted by pharmacy closures [10,24], which is particularly concerning given the recent widespread closures [8,9,11]. Importantly, Vermont’s population geography is predominantly rural, with just one metropolitan region and parts of four micropolitan regions within the state.

Second, does the accessibility of pharmacies vary temporally over different days of the week and times of day on typical weekdays, Saturdays, and Sundays? In addition to spatial inaccessibility, rural residents are less likely than their metropolitan counterparts to have access to primary care providers during nights and weekends [25], potentially exacerbating existing geographic limitations. Recognizing the impact of time on healthcare accessibility, some spatial accessibility analyses of healthcare have evolved to investigate the temporal dimension of access [26–28]. However, we are not aware of any studies that have examined the spatial accessibility of pharmacies in a temporally explicit manner, leaving a critical gap given the time-sensitive nature of many pharmacy services.

Third, if differences in pharmacy accessibility between rural and non-rural towns exist, are urban-rural differences in access exacerbated outside of conventional business hours? Urban-rural spatial accessibility gaps may be exacerbated outside of normal business hours, supported by results from spatio-temporal access to pediatrics in Taiwan [29] and general practitioner surgeries in Whales [30]. Furthermore, rural patients seek after-hours urgent care less frequently than urban patients due to distance barriers [31,32] and bypass nearby clinics to seek primary care at more distant clinics with after-hours options in New Zealand [33].