Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
To maximize protection from the Delta variant and prevent possibly spreading it to others, get vaccinated as soon as you can and wear a mask indoors in public if you are in an area of substantial or high transmission.
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.

Science Briefs

Science Briefs
photo of gloved hand moving lab specimen

Updated: Vaccines and Vaccinations

COVID-19 vaccines and Protection Against Variants

Studies published since the last update that demonstrate currently approved and authorized mRNA vaccines provide protection against variants of concern, including the Delta strain that is now predominant in the United States. Vaccine effectiveness against hospitalization and death is high for all current SARS-CoV-2 variants; emerging data suggest lower effectiveness against confirmed infection and symptomatic disease caused by the Beta, Gamma, and Delta variants compared with the ancestral strain and the Alpha variant.

September 15, 2021

Updated: Transmission in Schools

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

Globally, K-12 schools and early care and education (ECE) programs used various, layered COVID-19 prevention strategies with in-person, hybrid, and virtual models of instruction and care during the 2020-2021 academic year.  Their experiences have contributed to our knowledge of the nature of SARS-CoV-2 transmission in schools, ECE programs, and their surrounding communities.

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.