It states that people should quarantine if they've been in close contact with someone who has COVID-19, "excluding people who have had COVID-19 within the past 3 months."
People who have tested positive for the virus don't need to be tested again for up to three months, as long as they don't develop symptoms again.
However, the update goes one step further, suggesting that people who have recovered are protected from getting sick again for at least three months.
Longer-term studies are needed to determine how long protection might last, and it's still too soon to say to whether a person who has had COVID-19 and recovered is immune.
He noted that the CDC's guidance shouldn't be over-interpreted "an an indication that we have or could soon achieve herd immunity."