Introduction

The first case of coronavirus disease 2019 (COVID-19) in Mexico was detected in Mexico City on February 27, 2020. ^{Reference Suárez, Quezada, Ruiz and De Jesús1} Less than one month later, on March 18, 2020, Mexico City reported the first confirmed COVID-19 death. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2} The rapidly increasing number of COVID-19 cases and deaths resulted in the issuance of several public health orders by the Mexican federal government in late March 2020. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2} The purpose of the public health orders was to prevent new infections and mitigate the impacts of COVID-19. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2} On March 23, 2020, the Mexican federal government ordered the closing of all schools. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2,Reference García-Guerrero and Beltrán-Sánchez3} The Mexican Ministry of Health (Guerrero, Mexico) also launched Sana Distancia, a program that initially encouraged physical distancing, although the term was later replaced by social distancing to emphasize the importance of staying physically apart, but socially connected. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2} On March 30, 2020, Mexico declared COVID-19 a national emergency, which resulted in the adoption of additional public health orders, including stay-at-home orders and partial suspension of non-essential activities, including leisure activities, public gatherings of more than 25 people, and public administration services. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2,Reference Hernández-Paniagua, Valdez and Almanza4} A total lockdown prohibiting any remaining non-essential activities was issued on April 21, 2020. ^{Reference Hernández-Paniagua, Valdez and Almanza4}

The COVID-19 pandemic and the issuance of public health orders resulted in people spending more time at home, disruptions in daily activities, such as driving, and mobility restrictions, including decreases in the availability of public transportation services. ^{Reference Sánchez-Talanquer, González-Pier, Sepúlveda, Abascal-Miguel, Fieldhouse, Del Rio and Gallalee2,Reference Hernández-Paniagua, Valdez and Almanza4,Reference Kutralam-Muniasamy, Pérez-Guevara, Roy, Elizalde-Martínez and Shruti5} At the national level, Mexico experienced a rapid decrease in the rates of traffic accidents, traffic injuries, and traffic fatalities, a finding that was, at least partially, influenced by more people staying at home. ^{Reference Balmori de la Miyar, Hoehn-Velasco, Silverio-Murillo and Tennyson6} The severity of traffic accidents, however, rose after the COVID-19 pandemic began. ^{Reference Balmori de la Miyar, Hoehn-Velasco, Silverio-Murillo and Tennyson6} Crimes also decreased substantially in Mexico during the COVID-19 pandemic, although variation was reported by type of crime. ^{Reference De la Miyar, Hoehn-Velasco and Silverio-Murillo7} The reduction in crime was partially attributed to changes in mobility, including decreases in public transportation availability and public transport passenger numbers. ^{Reference De la Miyar, Hoehn-Velasco and Silverio-Murillo7,Reference Estévez-Soto8}

The Mexican health care system was also drastically impacted by the COVID-19 pandemic and the issuance of public health orders. ^{Reference Vilar-Compte, Hernández-F, Gaitán-Rossi, Pérez and Teruel9,Reference Doubova, Leslie, Kruk, Pérez-Cuevas and Arsenault10} A study reported that the Mexican Institute of Social Security (IMSS; Torreón, Mexico), Mexico’s largest national public health care institution, saw a decline of 8.74 million patient visits during the early COVID-19 pandemic period, January 2019 through December 2020. ^{Reference Doubova, Leslie, Kruk, Pérez-Cuevas and Arsenault10} As the COVID-19 pandemic progressed, in 2021, the use of IMSS health care services gradually increased. ^{Reference Doubova, Arsenault, Contreras-Sánchez, Borrayo-Sánchez and Leslie11} The COVID-19 pandemic was also associated with a decline in specialized care, including organ donations, waiting list additions, and organ transplantations. ^{Reference Servin-Rojas, Olivas-Martinez, Ramirez Del Val, Torres-Gomez, Navarro-Vargas and García-Juárez12}

Although research shows that the COVID-19 pandemic had detrimental impacts across the Mexican health care system, the prehospital care system remains largely under-studied. Prehospital care refers to health care services provided in an out-of-hospital setting, usually by emergency service personnel such as emergency medical technicians and paramedics. The prehospital care system serves as an important entry point into the Mexican health care system and provides a source of real-time data, which may be used to inform the COVID-19 response. ^{Reference Friedman, Calderón-Villarreal, Bojorquez, Hernández, Schriger and Hirashima13} The declaration of 9-1-1 as the unified emergency number in Mexico since November 2014 also facilitates prehospital care research, although its implementation has varied by state. ¹⁴ Mexico City, for example, began using 9-1-1 as the single emergency number starting in January 2017. ¹⁴ Prior to the establishment of 9-1-1 as the unified emergency number in Mexico, accessing emergency services required dialing different telephone numbers based on the type of emergency. ¹⁴ The unified 9-1-1 emergency number in Mexico standardizes the approach to emergency service data collection, which facilitates prehospital care research.

This study focuses on prehospital care in Mexico City by examining injury-related 9-1-1 emergency calls before (January 1, 2019 through June 30, 2019) and during the COVID-19 pandemic (January 1 through June 30, 2020 and 2021). Previous studies suggest decreases in injury-related 9-1-1 emergency calls, although this is the first study to examine this outcome in Mexico City. ^{Reference Handberry, Bull-Otterson and Dai15,Reference Lerner, Newgard and Mann16} Furthermore, existing studies on injury-related 9-1-1 emergency calls limit their analysis to 2020, the first year of the COVID-19 pandemic, while this study expands the analysis to the first six months of 2021. ^{Reference Handberry, Bull-Otterson and Dai15,Reference Lerner, Newgard and Mann16} In this study, traffic accidents and crime are examined because these incidents account for over one-half of the injuries in Mexico City. ^{Reference Dávila-Cervantes and Pardo-Montaño17} Previous studies have reported steep declines in traffic accidents and crime in Mexico City starting in March 2020, which may partially explain a decrease in injury-related 9-1-1 emergency calls during this time. ^{Reference Balmori de la Miyar, Hoehn-Velasco, Silverio-Murillo and Tennyson6} This study adds to existing research on traffic accidents and crime because it examines the data at both the state-level (Mexico City; Appendix A – available online only) and the borough-level (Appendix B – available online only). This study has three objectives. The first objective is to examine monthly per capita rates of injury-related 9-1-1 calls, traffic accidents, and crime at the state-level (Mexico City) during the early pandemic period (January 1 through June 30, 2020). The second objective is to assess monthly per capita rates at the borough-level for the same outcomes and time period as the first objective. The first two objectives focus on the early pandemic period to consider changes in the monthly per capita rates across the three outcomes, before, immediately after, and three months post-issuance of the first major wave of public health orders in Mexico City in March 2020. The third objective examines monthly per capita rates for the three outcomes of interest at the state-level (Mexico City) during the pre-pandemic (January 1 through June 30, 2019), early pandemic (January 1 through June 30, 2020), and later pandemic periods (January 1 through June 30, 2021).