Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
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.

Science Briefs

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

Updated: Transmission in Schools

Science Brief: Transmission of SARS-CoV-2 in K-12 Schools and Early Care and Education Programs – Updated | CDC 

December 17, 2021

Data were added from recent studies on Test to Stay (TTS) in K-12 schools. These studies demonstrated low transmission of COVID-19 in K-12 schools that implemented Test to Stay along with layered prevention strategies. Additionally, example criteria from school districts implementing TTS were added.

Updated: Community Use of Masks

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

December 6, 2021

New: Omicron (B.1.1.529) Variant

December 2, 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


Emerging SARS-CoV-2 Variants

Jan. 28, 2021

CDC's Science Agenda for COVID-19

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