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.

What We Know About Quarantine and Isolation

What We Know About Quarantine and Isolation

Quarantine and Isolation: Learn the latest recommendations after COVID-19 exposure or if you are sick.

Why CDC Shortened Isolation and Quarantine for the General Population

COVID-19 cases due to the Omicron variant have increased along with seasonal increases in influenza and other respiratory virus infections. The potential for a large number of cases raises serious concerns about societal impact due to illness, as well as isolation and quarantine requirements [1]. CDC has been monitoring the emerging science on when and for how long a person is maximally infectious with Omicron, as well as the effectiveness of COVID-19 vaccines and booster doses against Omicron infection. Data related to the mental health effects of the pandemic and adherence to prevention interventions have also been considered.

Data, including a review of 113 studies from 17 countries, show that most SARS-CoV-2 transmission occurs early in the course of infection [2,3]. Infectiousness peaks around one day before symptom onset and declines within a week of symptom onset, with an average period of infectiousness and risk of transmission between 2-3 days before and 8 days after symptom onset [2,3]. These data are from studies of prior SARS-CoV-2 variants, including Delta. The science is evolving, particularly for the Omicron variant, and some reports suggest that compared with previous variants, Omicron has a shorter incubation period (2-4 days), defined as the time between becoming infected and symptom onset [4-6]. Hospitalization and death rates are much lower for vaccinated people for all SARS-CoV-2 variants; preliminary data from South Africa suggest that hospitalization and death rates are lower for people infected with Omicron compared with other variants[7-9].  Early estimates of lower vaccine effectiveness (VE) against symptomatic infection and disease due to Omicron after the Pfizer-BioNTech primary series and improved VE after booster doses suggest that booster doses are important to improve protection from hospitalization and death due to infection with the Omicron variant [10-14].  Spread of the Omicron variant has the potential to worsen staffing shortages and increase supply chain challenges, which jeopardize industry, education, and other systems that are essential to maintain a functioning society and economy. The pandemic has also had a negative impact on the mental health of adults in the United States [15], largely due to economic and social concerns [16]. Although many people have intentions to self-isolate, both isolation and quarantine are challenging; especially in the context that many infections are asymptomatic [17]. Studies suggest that only a small percentage of people (25-30%) isolate for a full 10 days [18,19].

On January 4, CDC updated COVID-19 isolation and quarantine recommendations with shorter isolation (for asymptomatic and mildly ill people) and quarantine periods of 5 days to focus on the period when a person is most infectious, followed by continued masking for an additional 5 days. These updated recommendations also facilitate individual social and well-being needs, return to work, and maintenance of critical infrastructure. Preliminary data suggest that the Omicron variant is up to three times more infectious than the Delta variant [20]. With the recommended shorter isolation and quarantine periods, it is critical that people continue to wear well-fitting masks and take additional precautions for 5 days after leaving isolation or quarantine [21]. In addition, isolation should only end if a person has been fever-free for at least 24 hours without the use of fever-reducing medication and other symptoms have resolved. Modeling data from the United Kingdom reinforce the importance of mask use; after the 5th day after a positive test, an estimated 31% of persons remain infectious [22]. Mask use and layered prevention strategies, such as receiving all recommended vaccination and booster doses, physical distancing, screening testing, and improved ventilation, are key to preventing COVID-19 and decreasing transmission.

Frequently Asked Questions

  1. Potential Rapid Increase of Omicron Variant Infections in the United States | CDC
  2. Meyerowitz EA, Richterman A, Gandhi RT, Sax PE. Transmission of SARS-CoV-2: a review of viral, host, and environmental factors. Ann Intern Med.external icon 2020 Sep 17: M20-5008.
  3. Peeling RW, Heymann DL, Teo Y, Garcia PJ. Diagnostics for COVID-19: moving from pandemic response to control. Lancet. Published online December 20, 2021: icon
  4. Centers for Disease Control and Prevention. Investigation of a SARS-CoV-2-B. (Omicron) Variant Cluster—Nebraska- November-December 2021.  MMWR Early Release. Vol. 70. December 28, 2021.
  5. Brandel LT, MacDonald E, Veneti L, Ravio T, Lange H, Naseer U, et al. Outbreak caused by SARS-CoV-2 Omicron variant in Norway, November to December 2021.Euro Surveill.2021;26(50):pii=2101147 icon
  6. Lee JJ, Choe YJ, Jeong H, Kim M, Kim S, Yoo H, et al. Importation and transmission of SARS-CoV-2 B1.1.529 (Omicron) variant of concern in Korea, November 2021. J Korean Med Sci. 2021 Dec 27;36(50):e346 icon eISSN 1598-6357·pISSN 1011-8934
  7. Maslo C, Friedland R, Toubkin M, Laubscher A, Akaloo T, Kama B. Characteristics and outcomes of hospitalized patients in South Africa during the COVID-19 Omicron wave compared with previous waves. Published online December 30, 2021. icon
  8. Christensen PA, Olsen R, Long SW, Snehal R, Davis JJ, Saavedra MO, et al. Early signals of significantly increased vaccine breakthrough, decreased hospitalization rates and less severe disease in patients with COVID-19 caused by the Omicron variant of SARS-CoV-2 in Houston TX. medRxiv. icon
  9. Lewnard JA, Hong VX, Patel MM, Kahn R, Lipsitch M, Tartof SY. Clinical outcomes among patients infected with Omicron (B.1.1.529) SARS-CoV-2 variant in southern California. medRxiv. 2022. icon
  10. Andrews N, Stowe J, Kirsebom F, Toffa S, Rickeard T, Gallagher E, et al. Effectiveness of COVID-19 vaccines against the Omicron (B.1.1.529) variant of concern. medRxiv.2021. icon
  11. Collie S, Champion J, Moultrie H, Bekker LG, Gray G. Effectiveness of BNT162b2 vaccine against Omicron variant in SA.NEJM. December 29, 2021 icon
  12. Hansen CH, Schelde AB, Moustsen-Helm IR, Emborg HD, Krause TG, Mølbak K, et al. Vaccine effectiveness against SARS CoV2 infection with the Omicron variant Danish study. medRxiv. icon
  13. Nemet I, Kliker L, Lustig Y, Zuckerman N, Erster O, Cohen C, et al. Third BNT162b2 vaccination neutralization of SARS-CoV-2 Omicron Infection. NEJM. December 29, 2021 icon
  14. Schmidt F, Muecksch F, Weisblum Y, Da Silva J, Bednarski E, Cho A, et al. Plasma neutralization of the SARS-CoV-2 omicron variant. NEJM. December 30, 2021. icon
  15. Ettman CK, Abdalla SM, Cohen GH, Sampson L, Vivier PM, Galea S. Prevalence of depression symptoms in US adults before and during the COVID-19 pandemic. JAMA Network Open2020;3(9):e2019686. icon
  16. Kämpfen F, Kohler IV, Ciancio A, Bruine de Bruin W, Maurer J, Kohler H-P. Predictors of mental health during the Covid-19 pandemic in the US: Role of economic concerns, health worries and social distancing. PLoS ONE 2020 15 (11): e0241895. icon
  17. Ma Q, Liu J, Liu Q, Kang L, Liu R, Jing Q, et al. Global percentage of asymptomatic SARS-CoV-2 infections among the tested population and individuals with confirmed COVID-19 diagnosis. JAMA Netw Open2021;4(12):e2137257. icon
  18. Smith LE, Potts HWW, Amlôt R, Fear NT, Michie S, Rubin GJ. Adherence to the test, trace, and isolate system in the UK: results from 37 nationally representative surveys. : BMJ 2021;372:n608 icon
  19. Smith LE, Amlôt R, lambert H, Oliver I, Robin C, Yardley L, Rubin GJ. Factors associated with adherence to self-isolation and lockdown measures in the UK: a cross-sectional survey. Public Health 2020. 187:41-52. icon
  20. Ito K, Piantham C, Nishiura H. Relative instantaneous reproduction number of Omicron SARS-CoV-2 variant with respect to the Delta variant in Denmark. J Med Virol. 2021 Dec 30. icon
  21. Science Brief: Community Use of Masks to Control the Spread of SARS-CoV-2 | CDC
  22. Bays D, Whiteley T, Pindar M, Taylor J, Walker B, Williams H, Finnie TJR, Gent N. Mitigating isolation: the use of rapid antigen testing to reduce the impact of self-isolation periods. medRxiv. 2021. icon