Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
UPDATE
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.
UPDATE
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.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

Science Briefs

Science Briefs
Updated Dec. 17, 2021
photo of gloved hand moving lab specimen

COVID-19 Science Briefs provide a summary of the scientific evidence used to inform specific CDC guidance and recommendations. The Science Briefs reflect the scientific evidence, and CDC’s understanding of it, on a specific topic at the time of the Brief’s publication. Though CDC seeks to update Science Briefs when and as appropriate, given ongoing changes in scientific evidence an individual Science Brief might not reflect CDC’s current understanding of that topic. As scientific evidence and available information on COVID-19 change, Science Briefs will be systematically archived as historic reference materials.

Updated: COVID-19 Community Levels

Science Brief: Indicators for Monitoring COVID-19 Community Levels and Making Public Health Recommendations

August 11, 2022

This science brief provides an overview of how CDC’s COVID-19 Community Levels framework was developed, the data sources it uses, and how jurisdictions can use the information to monitor COVID-19 Community Levels and inform public health action. A comprehensive approach to assessing COVID-19 community levels can inform decisions about layered COVID-19 prevention strategies, including vaccination and masking, with explicit goals of reducing medically significant disease and limiting strain on the healthcare system.

Updated: Community Use of Masks

Community Use of Masks to Control the Spread of SARS-CoV-2

December 6, 2021

Updated: Vaccines and Vaccinations

SARS-CoV-2 Infection-induced and Vaccine-induced Immunity

October 29, 2021

Updated: Vaccines and Vaccinations

COVID-19 vaccines and Protection Against Variants

September 15, 2021

Updated: Transmission in Schools

Transmission of SARS-CoV-2 in K-12 schools

July 8, 2021

Vaccines and Vaccinations

Science Brief: COVID-19 Vaccines and Vaccination

May 27, 2021

Updated: SARS-CoV-2 Transmission

Scientific Brief: SARS-CoV-2 Transmission

May 7, 2021

Updated: Underlying Medical Conditions

Scientific Evidence for Conditions that Increase Risk of Severe Illness

March 29, 2021

CDC's Science Agenda for COVID-19

Learn more about the high-level framework for planning and prioritization of COVID-19 work.