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- If you're vaccinated and exposed to COVID-19, most of the experts Insider spoke to said you don't need to worry unless you have symptoms.
- You should get tested if you're symptomatic, but some experts say to get tested after any exposure.
- If you're sick, stay away from others – even if it's not COVID.
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So your roommate has a cold.
You both got vaccinated months ago, yet every time you hear a cough from the next room, you can't help but wonder if you should get tested for COVID.
Most public health experts would say you're in the clear – probably not sick and probably not infectious – unless you start to feel symptoms. (Your ailing roommate, however, should get tested.)
Although the COVID-19 vaccines are highly effective at preventing severe illness, "breakthrough" infections are occurring in fully vaccinated people. It might feel like a bad cold, or carry no symptoms at all.
The Delta variant has increased the odds of such an infection, but there are plenty of other viruses going around, Amesh Adalja, senior scholar at Johns Hopkins Center for Health Security, told Insider.
The only way to know for sure is to get tested. But if your roommate's test comes back positive for COVID-19, what do you do?
Get tested if you develop cold-like symptoms
If you develop a cough, congestion, or a loss of taste and smell after a known exposure, you should get tested regardless of your vaccination status.
Start with a rapid antigen test. In studies, rapid tests were about 72% effective at identifying COVID-19 in symptomatic people and correctly ruled out COVID for about 99.5% of people who had symptoms for other reasons.
You can also take a rapid test at home. They're more accurate if you get tested every few days, so if you're initially negative, you might want to test again to be sure. You could also follow up with a PCR test that looks for other viruses as well, Adalja added.
"You also have to remember that now that many people are socially interacting, other viruses have come back - things like rhinovirus and seasonal coronaviruses - so there are other causes of cold-like symptoms," Adalja said.
If you don't have symptoms, many experts say you're probably in the clear
The CDC recommend vaccinated people get tested or quarantine only if they have symptoms of COVID-19.
If you're symptom-free for more than a week after an exposure, you can relax, according to Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia.
"The only time you should get tested if you're fully vaccinated is if you're symptomatic, no matter what the exposure," Adalja said.
Charity Dean, a former top-tier official at the California Department of Public Health, told Insider she was "very disappointed" the CDC is not seriously tracking mild or asymptomatic infections in fully vaccinated people. Without that information, we risk missing a more dangerous "escape variant," Dean told Insider's Hilary Brueck.
So if you're making your decision with public health in mind, you may want to get tested even if you don't have symptoms.
Quarantine if you feel sick or test positive for COVID
COVID-19 or seasonal virus symptoms indicate that you could be infectious to others.
"If the virus reproduces itself well enough in you to cause symptoms, I think that means that you're likely to be contagious," Offit told Insider.
Vaccinated people who get COVID may be less contagious than unvaccinated infected people, if their reduced viral loads are any indication.
However, other experts recommend using common sense before deferring to CDC guidelines, which "lack nuance," emergency physician Leana Wen told CNN.
"I don't want someone coming into work, who then tells me that they just spent the entire night caring for their spouse who's ill from COVID," Wen told CNN. "Should that person really be in a crowded conference room with a whole bunch of other people? Does that sound right? It doesn't meet the common sense test."
One thing experts generally agree on: stay away from people if you're not feeling well.
The norms of the pandemic - mask-wearing, quarantining - still apply if you're sick and it's not COVID-19. But if you're vaccinated and feeling fine, there's no need to worry, Offit said.
"I think we're going to drive ourselves crazy if we're expecting this vaccine to prevent asymptomatic or mildly symptomatic disease," Offit said. "Just use common sense. If you develop respiratory symptoms, I think it's probably a good idea to wear a mask."