Ed note: The Omicron variant and its variants are upon us. The CDC in this updated Feb. 2022 publication explains the need to balance isolation with the need to get on with life. Masking is very important (high quality N95 or KN95 masks are best) as the shortening of isolation has been implemented. Since we will continue to have COVID infections for the indefinite future, please MASK UP!
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.