Description of studies

Figure 1 presents the selection studies for the review (Fig. 1). The search strategy returned 5849 articles/studies, including the grey literature and forward citation searches. After duplicates were removed, 3827 articles were screened for relevance based on title and abstract, where 2022 articles were excluded, leaving 83 articles for full-text screening. A further 19 articles were excluded after the full-text screen. A total 64 studies were included in the final review. Of 64 studies, 47 were related to outbreaks, mostly explaining the COVID-19 pandemic. Seven studies explained complex emergencies (e.g., concurrent conflicts, outbreaks, and disasters), six discussed conflicts, and four explained disasters caused by natural hazards.

Fig. 1

PRISMA-ScR flow chart showing the selection of studies for the review

Main themes from the included studies

Several themes were identified regarding the impacts of PHEs, and lessons learned while responding to those PHEs. Table 2 presents themes on preparedness, impacts, and response of PHEs towards health security.

Table 2 Preparedness, impacts and lessons learned in responding to public health emergenciesPreparedness

Preplanning, ensuring monitoring and surveillance of PHEs are key to reducing the potential consequences of PHEs. There were several examples of preparedness and surveillance in different contexts.

Preparedness and surveillance

Health systems have faced several challenges in disaster preparedness. Those challenges included a shortage of staff and supplies, poor preparation facilities for emergencies, lack of electricity backup, and missing standard operating procedures and policies [31,32,33,34,35,36]. Other hindering factors for disaster preparedness were poor transportation, inadequate communication, and incident command systems [33,34,35,36]. For example, Cameroon’s weak PHC systems with inadequate preparedness for PHEs hindered the health response systems and recovery strategies during and following the COVID-19 pandemic [37].

In conflicts and disasters, critical knowledge gaps and context-specific challenges in health systems (e.g., governance, financing, workforce, accountability, and service coordination mechanisms) affected the PHC implementation [13]. In natural disasters, poor understanding of PHC of stakeholders from non-health sector and the health sector’s silo approach also influenced integrated disease management [16, 38]. Lack of planning and defining the roles of professionals and disarticulating actions with real needs hampered the PHC services delivery to the COVID-19 pandemic-affected populations in many countries [39].

Nevertheless, there were some successful examples of preparedness for PHE responses. For instance, Indonesia’s decentralised health system governance and strengthening (e.g., national action plans for health security, preparedness planning and exercises) enhanced emergency preparedness strategies [25]. These strategies included mandatory minimum standards at a local level, integrated with a national disaster management system, decentralised contingency plans, and simulation exercises for potential future PHEs. In China, the experience of the city of Shenzhen in coordinating their health care systems’ preparedness helped other cities to enhance and deal with response capacities in future emergencies [26]. In Japan, daily reporting of post-disaster disease surveillance was critical for tailoring responses to local settings, establishing support networks, and integrating resources [27]. In addition, the proactive reorganisation of PHC services paved the way towards increased pandemic preparedness, planning, surveillance and responses for future health system shocks [28,29,30].

Impacts of public health emergencies

The PHEs have direct impacts (e.g., interruption of supply chain and health service delivery) and indirect (e.g., collateral impacts including damage to infrastructure, road networks, and communication systems). These impacts led to creating structural and health inequities.

Increased health needs

During the armed conflict, there have been increasing numbers of internally displaced persons and refugees, leading to overcrowding and overburden for existing systems and service delivery. For example, in the Democratic Republic of the Congo (DRC), conflicts further triggered an increase in Ebola cases that overburdened health systems and increased health service needs [33].

Displaced populations due to armed conflicts need health services that could lead to overburdened health systems, interruption of health service delivery, and challenges in the implementation of PHC. Some implementation challenges of PHC in PHE contexts including armed conflicts covered under-preparedness and lack of shock absorption capacity in public sector, limited ability to provide services, poor adaptation to shocks, lack of restructuring of damaged facilities, limited resilience to conflict difficulties, and rebuilding community trust in the public sector [31, 32].

Furthermore, displaced and host populations in conflict-affected settings both lacked public health services and experienced further exposure to the risk of infections and mental health issues [33, 40]. Those affected populations had poor access to hygiene and sanitation (e.g., access to safe water) and lacked access to PHC services [33, 40]. For instance, in Libya, the impact of conflicts was structural damage to health facilities, shortage of medical supplies, lack of security of PHC staff, and lack of communication, all of which collectively led to an increase in neglected and orphaned children and the emergence of unusual infections [41]. In DRC, there were no integrated community mental health services despite increased mental health problems due to armed conflicts [33].

Armed conflicts had collateral damage in the context of fragile health systems that further influenced the access and delivery of health services. For instance, in Yemen, the ongoing war has increased cholera outbreaks affecting the health system to meet those health needs [42]. In armed conflict-affected regions such as the Ebola epidemic in Guinea, Sierra Leone, and Liberia, health systems became fragile, which deteriorated the provision of essential public services to both displaced and host populations [43]. Furthermore, conflicts also affect care-accessibility by interrupting the supply chain management and short-term programs [42, 44]. Factors affecting health care delivery in conflict affected settings included lack of integrated community health, difficulties in travel, poor supervision and monitoring, threats to health workforces, weak supply chain management capacity, unavailability of quality services, politicization of aid, and increased costs of care [42, 44]. In addition, civil instability and natural disasters resulted in individuals abandoning or postponing routine care, including mental health services [33, 45].

Constraints of service delivery

Several health system factors create difficulties in health service delivery in PHEs. For example, in Australia, a lack of trained PHC workforces increased the risk of transmission of COVID-19 in remote areas [46]. Failure of coordinated support in PHC services overburdened hospital services and overcrowding increased the chance of nosocomial infections in Lombardy, Italy [47]. Furthermore, disturbance in PHC systems increased cases without PHC services in preventing and controlling outbreaks in Brazil [48]. For example, in Malawi, key health services were interrupted, reducing clients attending facilities in PHEs [51]. Instead, the priority was given to the hospital sector, resulting in the poor and ill-equipped first point of care to protect staff and patients from infection and provide primary care [45, 48].

Furthermore, PHEs resulting from catastrophic events impacted the roles of the health workforce (e.g., task-shifting responsibilities and changes in the scope of work, financial strains, daily uncertainties, and stress). They hindered the delivery of primary care services [49, 50]. Neglected or postponed essential care, lack of gatekeeping, limited capacity, and weak integration between medical care and public health influenced factors of delivery of patient care services [49, 50]. In Sub-Saharan Africa, insufficient investment in health systems and increased pandemic is a reminder that non-communicable diseases, which are increasingly prevalent, are closely interlinked to the burden of communicable diseases that exacerbated poor health outcomes such as morbidity and mortality [15].

Countries like Cameroon and the CAR had hot spots of emergency outbreaks but lacked PHC services as blind spots of outbreak response [28, 37]. New epidemic outbreaks in Ecuador were exacerbated by a lack of preparation, poor information on health indicators, a shortage of resources (personnel and physical infrastructure), poor PHC services, and a sharp increase in pre-existing diseases [34]. During the pandemic, health systems had the availability of comprehensive services and adaptation to unique demands of resources. In contrast, people’s lives and the economy were impacted by service users’ discrepancies between reported behaviour and practice (e.g., consistent use of masks) [45, 51]. Furthermore, political disputes and constraints of financial resources in strengthening the PHC system hampered and obscured primary care, which influenced the health systems’ capacity to address health needs and effectively implement infection control protocols [28, 37]. In the case of Ebola response and infection control in Guinea, Sierra Leone, and Liberia, conflicts weakened primary care systems and contributed to the fast and rapid spread of diseases [43].

Multiple impacts on building blocks

PHEs broadly – and COVID-19 specifically – impacted all building blocks of health systems. Firstly, health systems lacked facility readiness for health services, including lack of material resources (e.g., soap, hand sanitiser, water, masks, equipment, test materials, and staff), inadequate infrastructures (e.g., lack of equipment and space), difficulties with procurement of test kits and turn-around times, neglected PHC systems, poor health service provisions, and inadequate management of cases and physical distancing [47, 51, 52].

Second, COVID-19 hindered the delivery of PHC services and health care deficiencies due to continued isolation, lockdown, and restriction of critical services, especially in remote areas in Australia [53, 54]. The COVID-19 pandemic amplified the fragility of existing systems, caused a de facto lockdown and associated collateral damage, and disrupted traditional delivery models in Sub-Saharan Africa and South Africa [53, 55,56,57,58]. Following natural disasters, damage to health infrastructure has contributed to the eruption of post-disaster disease outbreaks in Ecuador and Ebola-affected countries in Africa [33, 34].

Third, there was an impact on the health workforce, including a shortage of clinical workforce; fatigue and stress from heavy workloads, stigma, worries of infection, burnout, grief; and lack of training of junior doctors [33, 34, 47, 50, 51, 55,56,57,58]. For example, during the COVID-19 pandemic, the Australian health system experienced an acute shortage of health workforce (e.g., nurses) and relied heavily on short-term workforce such as fly-in, fly‐out/drive‐in, drive‐out staff to provide care in the country’s remote regions [46].

Fourth, during the COVID-19 pandemic, health systems response failed to consider or deal with their fears and ability to care for patients when confronted with poor data quality and inappropriate administrative decisions on self-standing field hospitals and information gaps [52, 56]. Modern health care systems are highly vulnerable to the unavailability of digital communication tools [16, 27]. Implementing remote consulting was challenging due to poor digital interoperability (e.g., lack of digital infrastructure and resources). High data or airtime costs affected upscaling, training, and providing care and health education [60, 61].

Finally, current global health systems are guided by the market-oriented political economy of health systems, which created difficulties in providing PHC services in a pandemic [62]. Community engagement and buy-in are critical for maintaining service provision in emergency contexts. For example, South Africa faced challenges in COVID-19 response related to poor partnerships between health systems and communities, as well as inadequate investment in PHC from the private health sector [56]. Lessons learned from past and current pandemics show that the failed responses of global health systems might create difficulties in handling future pandemics [63, 64]. Health systems also struggle with poor governance, including increased corruption in procurement at the country level [60]. Drivers of poor governance included chronic under-investment, insufficient workforces, lack of coordination in plan and funding programs, inflexible billing and record-keeping systems, and limited community awareness [44, 60]. As a result, the private sector may not invest in future PHEs responses and be disincentivized from investing in such opportunity costs in shifting resources away from commercial projects [43]. Poor capacity, including lack of resources, infrastructure, and reactive responses, for PHEs threatened the realisation of universal health coverage. Factors influencing poor public health response of PHCs were lack of coordinated efforts (primary care and public health), lack of resource coordination, and poor readiness of public health institutions [29, 52, 59].

Increased health inequities

Impacts of PHEs and globalization in trade and commerce also influence structural determinants of health. Unequal distribution of social determinants of health contributes to new inequities and increases existing equity gaps among priority populations. PHEs reduce access to services, especially marginalised people, and disproportionately exacerbate structural (e.g., education and wealth) and geographical disparities that lead to increased health inequities [31, 39, 62, 64]. Other impacts of PHEs (e.g., outbreaks) included the digital divide (e.g., exclusion of some populations due to digital and Wi-Fi access), unequal use of services offered, and compounded, long-standing health discrepancies [39,