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FAQ: Positive tests: Isolation, quarantine, and re-testing

What happens after a positive test?

A positive PCR test has implications for both that individual and their close contacts. Here’s what happens in each case.

I have no symptoms. Isolate for at least 5 full days after first positive test. Then wear a well-fitting mask at all times around others for an additional 5 days.
I have symptoms of COVID-19. Isolate for at least 5 full days after symptom onset and until fever free for at least 24 hours. Then wear a well-fitting mask at all times around others for an additional 5 days.
I am a close contact, and I am:
  • Fully vaccinated and boosted, if eligible or tested positive for COVID-19 within the last 90 days: No quarantine necessary. Get tested at least 5 days post exposure or if symptoms develop; self-monitor daily for symptoms through Day 10.
  • Unvaccinated or vaccinated but not up to date on COVID-19 vaccination including booster: Quarantine for at least 5 full days from last potential exposure; Get tested 5 days post exposure or if symptoms develop; self-monitor daily for symptoms through Day 10.

January 11, 2022

If I don’t have symptoms, why won’t you do a second test to confirm that the first was not a “false positive?”

Public health authorities consider a positive PCR test to be a true positive, so a subsequent negative test would not change the requirement for isolation. Research has shown that infected individuals may be asymptomatic but still able to spread the virus.

December 21, 2021

How long will I have to isolate after a positive test?

At least 5 days. If you are:

  • Asymptomatic: Isolate for 5 days after the first positive test. Then wear a well-fitting mask at all times around others for another 5 days,
  • Symptomatic: Isolate for at least 5 days after symptom onset or until you have been fever free for at least 24 hours, whichever is longer. Then wear a well-fitting mask at all times around others for another 5 days,

January 11, 2022

I’ve tested positive for COVID-19 infection; how soon do I need to be tested again?

Once you’ve tested positive for the virus, you do not need to be tested again for 90 days from symptom onset, if you became ill, or from the date of your positive test, if you remained asymptomatic.

However, if you develop symptoms of COVID-19 during that three-month period, and if clinicians cannot identify another cause for these symptoms, you may need to be re-tested at that time.

January 21, 2021

What is a “close contact?”

The CDC defines a “close contact” as “someone who was within six feet of an infected individual for a cumulative total of 15 minutes or more over a 24-hour period starting from 2 days before illness onset (or, for asymptomatic patients, 2 days prior to specimen collection) until the time the patient is isolated.”

October 21, 2020

I’ve been in close contact with someone who has tested positive; how long do I need to self-quarantine?

If you are up to date on your COVID-19 vaccinations, including a booster shot, if eligible, or if you have had a positive test for COVID-19 in the last 90 days, CDC guidelines do not require you to quarantine, but you should be tested at least 5 days following the date of your exposure and monitor yourself for symptoms for 10 days. If you develop symptoms, you should self-isolate and be tested as soon as possible.

If you are not vaccinated or are not up to date on your COVID-19 vaccinations, including a booster shot, if eligible, you must self-isolate for a full five days and then test. Even if you are negative, you should continue to wear a well-fitting mask around others at all times for another five full days..

While you are quarantining, you must actively monitor yourself for symptoms and take your temperature at least once every day. You must continue this self-monitoring for a full 10 days from the date of your possible exposure to the virus, even after your 5-day quarantine has ended. If you develop even mild symptoms, you must immediately self-isolate and contact MIT’s contact-tracing team to arrange testing.

Unless you develop symptoms, you do not need to be tested during the quarantine period. However, if you want to be tested, MIT’s contact tracers will work with you to schedule your test.

January 11, 2022

If I’ve been vaccinated against COVID-19, do I still have to quarantine if I am identified as a close contact to someone who tests positive?

It depends. If you are eligible for a booster but have not yet received one, you are required to quarantine for 5 days. However, if you are up to date on your COVID-19 vaccinations, including a booster shot, if eligible, MIT and CDC guidelines do not require you to quarantine, but you should be tested at least 5 days following the date of your exposure and you should monitor yourself for symptoms for a full 10 days. If you develop symptoms, you should self-isolate and be tested as soon as possible.

January 11, 2022