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CDC says delta variant easily transmissible, recommends universal masking in school

July 27, 2021

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Everyone in schools and those living in areas with substantial or high COVID-19 disease transmission should wear a mask in public indoor settings regardless of their vaccination status, according to new guidance from the Centers for Disease Control and Prevention (CDC).

The updated public health recommendations are based on new information on the delta variant from several states and other countries showing that on rare occasions, fully vaccinated individuals infected with the variant may spread the virus to others, according to CDC Director Rochelle Walensky, M.D.

“This new science is worrisome and unfortunately warrants an update to our recommendations,” she said.

The updated recommendations align with AAP school guidance: both groups support keeping children safe and physically present in school and urge masking, vaccination and other layers of protection to prevent transmission.

Universal masking in school

The CDC recommends indoor masking for all teachers, staff, students and visitors to schools, regardless of vaccination status.

About 7.1 million children between ages 12 and 17 are fully vaccinated, representing 39% of 16- to 17-year-olds and 27% of 12- to 15-year-olds, according to an AAP analysis of CDC data.

Federal health officials hope more kids are vaccinated by the start of the school year.

Universal masking will help protect those who are not able to be vaccinated, such as children under 12, as well as those who are vaccinated but immunocompromised and not fully protected, Dr. Walensky said.

“The vast majority of transmission, the vast majority of severe disease, hospitalization and death is almost exclusively happening among unvaccinated people,” she said. “We still largely are in a pandemic of the unvaccinated.”

Delta is different

CDC officials say the authorized mRNA vaccines provide good protection against variants of concern, including the delta strain.

“We continue to estimate that the risk of a breakthrough infection with symptoms upon exposure to the delta variant is reduced by sevenfold; the reduction is 20-fold for hospitalizations and deaths,” Dr. Walensky said.

Fully vaccinated individuals in areas with low transmission may choose to wear a mask to protect household members who are unvaccinated, immunocompromised or at increased risk for severe disease.

The CDC recommends the following for fully vaccinated individuals:

  • Get tested if you have symptoms of COVID-19.
  • Test three to five days following a known exposure to someone with suspected or confirmed COVID-19 and wear a mask in public indoor settings for 14 days after exposure or until receipt of a negative test result.
  • Isolate if you have had a positive COVID-19 test in the prior 10 days or symptoms of COVID-19.
  • Wear a mask, keep 6 feet away from people outside your household and avoid crowds and poorly ventilated indoors spaces regardless of vaccination status if immunocompromised.

The recommendations apply to non-health care settings. Pediatricians and other health care personnel should refer to the CDC’s recommendations on infection prevention and control for health care settings.

Health Alert Network recommendations

The CDC also issued a health advisory urging public health practitioners and clinicians to increase COVID-19 vaccination coverage. Recommendations for health care practitioners include:

  • Clinical providers who are not fully vaccinated should get vaccinated as soon as possible.
  • Increase patient outreach efforts to encourage, recommend and offer COVID-19 vaccination.
  • Remind patients that vaccination is recommended for all people ages 12 years and older, even those with prior SARS-CoV-2 infection.
  • Follow trusted sources carefully for any new recommendations and changes in vaccine guidance.
  • Support efforts to ensure people receiving a first dose of a COVID-19 mRNA vaccine (i.e., Pfizer-BioNTech or Moderna) return for their second dose.
  • Communicate with unvaccinated staff, patients and other individuals to increase confidence in vaccination,
  • Recommend that fully vaccinated immunocompromised patients practice prevention measures for unvaccinated people.


  • CDC Guidance for Implementing COVID-19 Prevention Strategies in the Context of Varying Community Transmission Levels and Vaccination Coverage,
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