Global Responses to the COVID-19 Pandemic

worldwide were forced to rapidly adjust their public health systems, platforms, and tools to respond to COVID-19. The US Centers for Disease Control and Prevention (CDC) and its global partners adapted health systems and programs originally developed for other purposes, such as controlling the HIV/AIDS pandemic through the US President’s Emergency Plan for AIDS Relief (PEPFAR), Global Health Security Agenda implementation, influenza surveillance, and vaccine-preventable disease elimination and eradication. This special supplement of Emerging Infectious Diseases highlights responses to the early phases of the COVID-19 pandemic from >80 countries, spanning 6 continents and representing >130 organizations. This article summarizes global adaptations of core public health functions during COVID-19: surveillance, information, and laboratory systems; workforce, institutional, and public health capacity; and clinical and health services delivery.

tries and 3 regions (15). Since 2013, CDC has offered the PHEM Fellowship to develop an international emergency response workforce; an assessment examined PHEM graduates' roles during the pandemic (17). Zuber et al. reviewed the pivotal role NPHIs have played in pandemic response and identify gaps and priorities for further research (18).
Longstanding partnerships with MOH and other governmental bodies helped strengthen COVID-19 response capacity in Kenya (19), Nigeria (20), South Africa (21), and Cameroon (22). In Kenya, COVID-19 helped advance establishment of NPHIs and national and county-level emergency operations centers, workforce development and deployment, and training in surveillance, laboratory diagnostics, and infection prevention and control (IPC) (19). The Nigeria Presidential Task Force on COVID-19 worked with partners to develop a comprehensive National Pandemic Response Plan (20). In Cameroon, CDC's global health programs were leveraged to respond to COVID-19, helping ensure continued delivery of HIV services and other health programs (22). Through PEP-FAR, CDC used HIV Project Extension for Community Healthcare Outcomes programs, a model for virtual clinical mentorship, to address and assess healthcare workers' response to COVID-19 (23). In 2021, the Public Health Center of Ukraine, Ukraine's NPHI, engaged with faith communities to address public health measures during religious gatherings (24).

Clinical and Health Services Delivery and Impact
The pandemic also affected clinical and health services delivery. This supplement describes impacts on vaccine-preventable disease surveillance (25), expansion of COVID-19 vaccinations (26), and the effects of decreased hepatitis B immunization coverage (27). In the WHO Africa region, more than 200 Stop Transmission of Polio (STOP) Program consultants were surveyed to clarify how vaccine-preventable disease surveillance systems were disrupted during the pandemic (25). CDC's COVID-19 International Vaccine Implementation and Evaluation program applied lessons learned from Ebola, influenza, and meningococcal serogroup A conjugate vaccine introductions for the delivery of COVID-19 vaccines (26). Experiences from past rubella vaccination programs (28), yellow fever and polio immunization campaigns for COVID-19 vaccine deployment and safety monitoring in Ghana (29), and the effectiveness of inactivated whole-virus COVID-19 vaccine among healthcare personnel in Peru (30) can also inform future responses. Zambia integrated COVID-19 vaccination at HIV treatment centers and combined activities planned for 2021 World AIDS Day to help increase vaccination outreach (31). Kimani et al. assessed IPC strategies and health facility readiness for responding to COVID-19 in Kenya, providing important data to guide IPC improvements (32). Gomes et al. described initiatives to strengthen IPC in healthcare facilities in 4 countries for the prevention of healthcareassociated transmission of SARS-CoV-2 (33).
COVID-19 affected other clinical services, including male circumcision for HIV prevention in sub-Saharan Africa (34) and care offered to survivors of sexual violence in Kenya (35). COVID-19 also caused clinical and socioeconomic impacts on agricultural workers in Guatemala (36). Protocols on community-based management of acute malnutrition in Uganda, Ethiopia, and Somalia needed modification to continue essential feeding services during the pandemic (37).

Conclusion
International responses to COVID-19 demonstrated diverse adaptations, effects, and some improvements to public health systems and institutions; long-term global partnerships and collaborations across technical domains were central. The articles in this supplement issue contribute to ongoing efforts to stop outbreaks at their source and advance health equity to make the world safer, healthier, and more prepared for future public health emergencies.