On December 27, 2021, the Centers for Disease Control and Prevention changed its guidelines for people isolating due to COVID-19 infections from 10 days to 5 days. Yet last week, the CDC published its own results showing that among people who begin isolation due to symptoms of COVID-19, 65-80 percent tested positive on days 5-7 of isolation and 40 percent tested positive through day 9––effectively casting doubt on the agency’s isolation guidelines. 

Epidemiologist, immunologist, and pathologist Michael Mina tweeted on February 25 that the agency’s data show “how POOR their own guidance is surrounding leaving isolation at 5 days w/o negative a rapid test.” He went on to say that the new data match his lab’s data.

MICHAEL MINA, MD, michael.j.mina@gmail.com, @michaelmina_lab. 
    Mina is the Chief Science Officer at eMed, a platform for online healthcare solutions. Previously, he was Assistant Professor of Epidemiology and Immunology and Infectious Diseases at the Harvard School of Public Health. 

    Mina: “Breakthrough infections become symptomatic very early after exposure, because of pre-existing partial immunity that leads to fevers and congestion, and this ultimately causes the ‘isolation clock’ to start earlier than in the pre-Omicron era. This means that, instead of symptoms starting when virus load is at peak, today, people are at their peak virus loads at 5 days since symptom onset, just as they are exiting isolation. In general, individuals in isolation who are planning to leave isolation at 5 days since symptom onset, per CDC recommendations, have perhaps the single greatest risk for spreading the virus compared to any other known group of people.

    “The CDC recommendations do not require a test to exit isolation and in so doing pose a serious risk to public health. By taking a loose stance on whether people should or should not test, the CDC recommendations confuse most Americans and serve to create a less safe workplace than a stance that strongly recommends testing before exiting isolation early.

    “The CDC has not done a great job at using up to date data for their recommendations, often falling on published data that is usually months out of date. The CDC should recognize this and update their guidance to strongly recommend or require a rapid antigen test before early exit of isolation.”