The Centers for Disease Control and Prevention updated its guidelines this week for what people should do if they’re exposed to or contract COVID-19, following new research that shows most transmission occurs early in the course of illness.

The update comes as people return home from holiday gatherings with friends and family, and schools prepare to reopen — as the highly contagious omicron strain continues to spread. The new guidelines, which reduce the amount of time asymptomatic people must quarantine at home after exposure, are an attempt to reduce the risk of transmission while minimizing the disruption to people’s daily routines.

“CDC’s updated recommendations for isolation and quarantine balance what we know about the spread of the virus and the protection provided by vaccination and booster doses,” CDC Director Rochelle Walensky said Monday in a statement. “These updates ensure people can safely continue their daily lives.”

Here’s what you should know:

What are the new CDC isolation guidelines after a positive COVID-19 test?

People who test positive for COVID-19 should isolate for five days — instead of the previously recommended 10 days.

If you do not have symptoms after five days, you can leave isolation so long as you continue to wear a mask when around other people for an additional five days. If you still have a fever after five days, you should stay home until it breaks.

These guidelines apply to everyone, regardless of vaccination status.

Why have CDC isolation guidelines changed to 5 days instead of 10?

The latest research shows that most COVID-19 transmission occurs shortly after someone contracts the virus. The virus is most contagious during the one to two days prior to the onset of symptoms and the first few days after symptoms develop, according to the CDC.

Do I still need to quarantine if I had an exposure to someone who tested positive?

It depends.

You do not need to quarantine after exposure and can instead wear a mask around others for 10 days if you:

  • Received both doses of the Pfizer or Moderna vaccine within the last six months.

  • Received the single-dose Johnson & Johnson vaccine within the last two months.

  • Have received a COVID-19 vaccine booster.

You should stay home for five days and wear a mask around others for another five days if you:

  • Received the Pfizer or Moderna vaccine more than six months ago and have not been boosted.

  • Received the Johnson & Johnson vaccine more than two months ago and have not been boosted.

  • Are unvaccinated.

Everyone should get tested five days after exposure. If you develop symptoms, stay home and get tested.

» READ MORE: Looking for a free at-home COVID-19 test in the Philly region? Demand is outstripping supply.

Do I have to test negative before coming out of isolation?

According to the new CDC guidance, it’s not necessary to test negative before returning to your daily routine, so long as you stay isolated for five days or until your symptoms subside and you no longer have a fever. However, some epidemiologists disagree with the new guidelines because it is possible for people to stay infectious for longer than five days.