Important update: Healthcare facilities
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Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

CDC Public Health Science Agenda for COVID-19

CDC Public Health Science Agenda for COVID-19

Building the Evidence Base for Ongoing COVID-19 Response

CDC is in the process of updating this page to align with the new COVID-19 Community Levels. Updates will be posted here when available.

Priority COVID-19 Public Health Science Questions

As the public health response to the COVID-19 pandemic continues to evolve, routine identification and dissemination of priority COVID-19 public health science questions can promote efforts by the Centers for Disease Control and Prevention (CDC) and public health partners to fill critical scientific gaps and inform evidence-based decision-making through public health surveillance and epidemiologic research. The priority questions outline the critical scientific gaps identified by the CDC COVID-19 Response, CDC programs, and other public health partners that, if addressed, could provide significant, timely, and measurable improvements in public health outcomes.

The CDC COVID-19 Response Strategic Science Unit (SSU) systematically collects input from multiple entities across the CDC Response and from external public health partners to identify and update these questions as part of the CDC Public Health Science Agenda for COVID-19. These questions have been updated approximately every 4 months since April 2021 to ensure their timeliness, relevance, actionability, and impact. To address these questions, CDC authors have published over 1,000 scientific articles, indexed by priority topic here: COVID-19 CDC Publications Database. This update presents input gathered during October–December 2021, and spans 7 topic areas:

7 Topics - Health equity

7 Topics - Vaccines

7 Topics - Variants

7 Topics - Prevention strategies

7 Topics - Testing

7 Topics - Natural history, transmission, breakthrough infections, and reinfections

Post COVID conditions and other health impacts

Within these topic areas, 14 priority public health science questions relate to the broad scope of CDC’s scientific work, both in the United States and globally, including public health surveillance, epidemiologic research, implementation science, and evaluation. These questions also relate to ongoing work in the broader scientific community (e.g., other government agencies, academics, the private sector). Other relevant questions are found in the complementary science agendas of other federal agencies, including National Institutes of Health (NIH)external icon and Environmental Protection Agency (EPA)external icon.

Importantly, these questions also serve to expand the evidence base to accelerate progress toward reducing COVID-19 disparities and achieving health equity (CDC COVID-19 Response Health Equity Strategy). A health equity priority question was added in December 2021 to address health equity research gaps that do not necessarily fall within the other priority questions; however, health equity science remains a fundamental consideration to all priority questions, and therefore there is some overlap in health equity science activities across questions.

Key activities: Key activities of public health importance that fall within the question domain are noted under each question.

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Health Equity

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Prevention strategies

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Natural history, transmission, breakthrough infections, and reinfections

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Post-COVID conditions and other health impacts

Background for the CDC Public Health Science Agenda for COVID-19

The COVID-19 pandemic is a formidable global public health challenge. Since the initial emergence of a novel coronavirus in late 2019, the spread of SARS-CoV-2 has been unrelenting, impacting nearly every aspect of society worldwide. The pandemic has required a substantial response by public health authorities at all levels.

The Centers for Disease Control and Prevention (CDC) is at the forefront of the public health response to the COVID-19 pandemic and is a respected source of data and information used by public health, medical, and policy decision makers. From the beginning of the pandemic, CDC has been working with a wide array of partners to advance understanding of COVID-19.

The CDC Public Health Science Agenda for COVID-19 builds on CDC’s ongoing pandemic-related work. Importantly, the COVID-19 pandemic has underscored long-standing health disparities and inequities in the United States. Data-driven strategies are essential to address these disparities and improve the health outcomes of people disproportionately affected by COVID-19.1 The work set out in The CDC Public Health Science Agenda for COVID-19 is predicated on the use of culturally and linguistically appropriate approaches and methods and inclusion of populations at increased risk for health disparities and inequities to help reduce the impact of COVID-19 in these communities.

Goal of The CDC Public Health Science Agenda

The goal of The CDC Public Health Science Agenda for COVID-19 is to guide the development of the evidence base needed to strengthen the public health actions, guidance, and policy essential to limit the spread and impact of SARS-CoV-2 and ultimately end the COVID-19 pandemic.

CDC’s role and the scope of The CDC Public Health Science Agenda

CDC is providing leadership and technical expertise in the prevention and control of the COVID-19 pandemic by:

  • employing public health fundamentals, including disease surveillance, laboratory detection, and epidemiologic investigation;
  • identifying and implementing public health interventions to reduce disease transmission and the mitigation of its impact on health and well-being;
  • developing evidence-based guidance and policies for disease prevention, detection, and control; and
  • engaging in effective communication strategies to optimize uptake of protective behaviors and recommended actions.2

These key functions underpin The CDC Public Health Science Agenda for COVID-19.

Organization of The CDC Public Health Science Agenda

The CDC Public Health Science Agenda for COVID-19 was initially organized around a framework of six Priority Areas:

For each of the six Priority Areas, a series of Objectives were described.

Priority Area I. COVID-19 Disease Detection, Burden, And Impact

Disease surveillance and laboratory detection are at the heart of CDC’s mission and fundamental to the COVID-19 public health response. They underpin CDC’s work with federal, state, tribal, local, and territorial (STLT), academic, and commercial partners to better understand the burden of COVID-19 disease and efforts to mitigate its diverse impacts, including the disproportionate impacts of COVID-19 on people at increased risk for health disparities and inequities. CDC supplements surveillance and laboratory methods with the modern tools of viral genomics and mathematical modeling.

  • Objective 1. Develop new, or modify existing, methods of epidemiologic surveillance for COVID-19
  • Objective 2. Develop and optimize testing for SARS-CoV-2
  • Objective 3. Utilize viral genomics to advance understanding of COVID-19 and mitigate its impact
  • Objective 4. Use mathematical modeling and other technological tools to forecast COVID-19 trends and measure the impact of interventions across a range of populations
  • Objective 5. Assess and limit the impact of the COVID-19 response on healthcare services and public health programs in domestic and international settings

Priority Area II. Transmission of SARS-Cov-2

Understanding how SARS-CoV-2 is transmitted and the important factors that can facilitate its spread among people in healthcare, workplace, and community settings has been a high priority for CDC since the earliest days of the pandemic. This essential information is used to develop and update guidance about effective strategies to prevent, contain, and mitigate COVID-19.

  • Objective 1. Refine understanding of SARS-CoV-2 transmission modes
  • Objective 2. Identify host and virus factors associated with person-to-person transmission
  • Objective 3. Assess and characterize transmission of SARS-CoV-2 across a spectrum of healthcare settings
  • Objective 4. Evaluate transmission of SARS-CoV-2 in non-healthcare workplace and community settings/populations
  • Objective 5. Evaluate transmission of SARS-CoV-2 between people and animals

Priority Area III. Natural History of SARS-Cov-2 Infection

The full spectrum of COVID-19 disease continues to unfold and confound in its clinical manifestations and requires careful study. CDC and its collaborators have been undertaking comprehensive clinical and laboratory investigations of confirmed cases across a range of age groups and populations to learn about the natural history of COVID-19 disease, associated medical complications, and the development of immunity.

  • Objective 1. Define the spectrum and clinical course of SARS-CoV-2 infection
  • Objective 2. Characterize the immune response in infected persons

Priority Area IV. Protection in Healthcare and Non-Healthcare Work Settings

Understanding and mitigating risks to patients, HCP, and non-healthcare workers across a range of settings is a high priority focus. CDC works to identify culturally and linguistically appropriate innovative strategies, tools, and practices which can supplement traditional infection control and worker safety measures to protect patients and reduce nosocomial and occupationally acquired SARS-CoV-2.

  • Objective 1. Improve and assess the effectiveness of personal protective equipment
  • Objective 2. Assess strategies to reduce transmission of SARS-CoV-2 in healthcare and non-healthcare work settings

Priority Area V. Prevention, Mitigation, and Intervention Strategies

CDC has disseminated a portfolio of prevention, mitigation, and intervention strategies tailored to specific settings and sectors to slow the spread of COVID-19 and protect individuals and communities. Evaluating the effectiveness of these strategies is critical to help refine public health guidance and recommendations. A key responsibility for CDC, in collaboration with STLT public health partners and academic and other researchers is monitoring the coverage, safety, and effectiveness of COVID-19 vaccines.

  • Objective 1. Evaluate individual- and community-level strategies to limit infection with SARS-CoV-2
  • Objective 2. Evaluate strategies to limit infection with SARS-CoV-2 in specialized settings or select populations
  • Objective 3. Develop methods to detect SARS-CoV-2 in the environment
  • Objective 4. Identify the most effective methods for contact tracing, testing, and monitoring
  • Objective 5. Evaluate travel-related interventions
  • Objective 6. Optimize the acceptability, coverage, safety, and effectiveness of COVID-19 vaccines

Priority Area VI. Social, Behavioral, And Communication Science

Effective communication requires community engagement; empowerment of individuals to take appropriate measures to reduce their risk; evaluation of risk communication methods and information gaps; and culturally and linguistically responsive materials and messengers. The effectiveness of risk reduction strategies, such as community mitigation or maximizing vaccine uptake, is dependent in part on understanding the barriers to implementation/acceptance, including economic and social determinants of health. Understanding the social, behavioral, and mental health impacts of the COVID-19 pandemic are as important as understanding the impacts to physical health.

  • Objective 1. Understand where people receive information about the pandemic
  • Objective 2. Optimize uptake of recommended behaviors and actions
  • Objective 3. Enhance CDC communication products and information tools
  • Objective 4. Assess the social and mental health impacts of the pandemic


  1. Populations of special focus include racial and ethnic minority populations; people living in rural or frontier areas; people experiencing homelessness; essential and frontline workers; people with disabilities; people with substance use disorders; people who are justice-involved (incarcerated persons); and non-U.S.-born persons.
  2. A CDC framework for preventing infectious diseases. See icon