A: The guidelines represent a “most bang for your buck” approach to preventing transmission of COVID-19 at the population level–but quarantining for 14 days is still the recommended and safest approach.
While our scientific understanding of how long it takes to develop COVID-19 symptoms after being exposed (science term: incubation period) still says up to 14 days, modelling data suggest that after 10 days, the risk of transmission–while not zero–is quite low.
So in the interest of making quarantine less burdensome and increasing how many people can comply with quarantine during the period when transmission risk is highest, two alternative strategies for ending quarantine have now been approved by CDC:
⭐⭐⭐Best strategy: Quarantine for 14 days after an exposure to someone with COVID-19.
⭐ Alternative strategy 1: Quarantine can end after day 10 without getting tested IF you have no symptoms.
⭐ Alternative strategy 2: Quarantine can end after day 7 IF you are tested inside 48 hours prior to the end of quarantine (that’s more or less days 5-7) AND a negative result has been received AND they have had no symptoms.
Quarantine cannot end BEFORE day 7, nor if the person’s test results are still pending.
Note these alternative strategies are NOT a stand-alone measure. With both strategies, we still need to:
🤒 Continue to monitor for symptoms through day 14,
🚫 Have had no symptoms at any point prior to ending quarantine,
😷 Wear a mask, social distance and avoid gatherings for the full 14 days, and
🛏️ Immediately self-isolate and contact our health care provider and local public health authority if symptoms do develop at any point up through day 14.
In reality, the protocols are not that different from just quarantining for 14 days, the previous recommendation. It is not a free pass to be in close contact with those outside your household sooner.
The guidance seems most useful for people who have speedy and ready access to testing–such as personnel at major hospitals, who may be facing staffing challenges. A slightly shorter quarantine there would make a major difference to being able to staff shifts. Many places are facing critical shortages in healthcare personnel, and staff shortages are one of the major limits for that whole “exceeding healthcare capacity” problem.
That said, the risk of transmitting to others after the shortened quarantine period is NOT zero. The models suggested that for 100 people who ended their quarantine period after day 7 and received a negative PCR test taken 48 hours before they stop quarantining, 4 of them would still be able to pass the virus on to others (range 3.1-11.9%). Risk is slightly higher if an antigen-based test is used, because those tests are a bit less reliable (5 in 100, range 3.1-11.9%).
For someone who ends their quarantine period after day 10 with no symptoms, and without getting tested, the risk of transmission to others is estimated to be around 1.5 in 100 (range 0.1-10.6%). These estimates assume people continue to monitor symptoms and isolate as soon as possible if symptoms appear. You can check out the range of non-zero risk for different alternative quarantines in the CDC link below.
Overall, if you are debating whether to visit your grandma for the holidays, it’s best to quarantine for 14 days. If you do use in a shortened quarantine period, still following the #SMART principles (Space, Mask, Air, Restrict, Time) is necessary.