Even if you’re fully vaccinated against COVID-19, it’s hard not to feel nervous when you hear about so-called breakthrough infections.  And since the arrival of the more contagious Delta variant, we’re hearing more reports of fully-vaccinated people in Rhode Island and other states with high vaccination rates testing positive for the coronavirus. Brown University last week announced new restrictions on indoor gatherings after 84 fully vaccinated students tested positive for COVID-19. Even with the Delta variant, experts say, the overall risks for the vaccinated remain especially small. Here’s what we know about breakthrough cases in Rhode Island, and how to think about the risks.

Do we know how many full-vaccinated Rhode Island residents have had breakthrough infections?

More than 710,000 Rhode Islanders, or 67% of all residents, are fully vaccinated against COVID-19, according to state health data. State health officials as of Wednesday had identified about 6,200 breakthrough cases among those residents. That’s less than one percent of all fully-vaccinated Rhode Islanders.

Are people with breakthrough infections becoming sick from COVID-19?

About 72% of Rhode Islanders identified with breakthrough infections had symptoms, which could mean the sniffles or something that resembles the flu. Severe illness is rare: only 314 people (5%) were hospitalized. More than one-in-four Rhode Islanders with breakthrough infections as of mid-September either reported they had no symptoms (14%) or their symptoms were unknown (14%), Joseph Wendelken, of the state health department, said in an email. And those are just the people we know about because they got tested. 

Has anyone with breakthrough infections died?

Forty-nine Rhode Islanders who were fully vaccinated and later contracted COVID-19 have died,  state health officials reported Wednesday. However, COVID-19 was only considered the leading cause of death in 15 of the cases reported as of mid-September, the latest available data. That’s compared with more than 400 unvaccinated Rhode Islanders who died of COVID-19 since the state began tracking breakthrough cases in February.

What do these breakthrough infections tell us about how well the COVID-19 vaccines are working?

The COVID-19 vaccinations are still highly effective in preventing severe illness, hospitalizations and deaths, said Jennifer Kates, of the nonprofit Kaiser Family Foundation in Washington, D.C. What’s changed, she said, is that the Delta variant is much more contagious, and even people who are vaccinated are more likely to become infected if they are exposed to this new version of the virus.  Yet even after the onset of the Delta variant, during this spring and summer, people who were not fully vaccinated against COVID-19 were five times more likely to become infected, and more than ten times more likely to be hospitalized or die due to the virus than those who were fully vaccinated, according to a recent study published by the CDC. 

What’s my risk of getting COVID-19 if I’m vaccinated?

The answer depends partly on where you live. New York Times columnist David Leonhardt did some math based on breakthrough data in Utah, Virginia and Washington state. Based on that data, he projected the chances of getting a breakthrough infection is about one in 5,000 per day.  In places with fewer COVID-19 cases, like the Northeast, he estimated the chances are probably less than 1 in 10,000. Dr. Ashish Jha, Dean of the Brown University School of Public Health, said in a Twitter post that if you live in a low-infection state like Rhode Island or Massachusetts, your risk of a breakthrough infection is probably closer to 1 in 20,000. Of course, your risk of being infected also depends on your personal exposure at work and in your social life. 

What are the chances of a vaccinated person with a breakthrough infection spreading COVID-19 to people who are unvaccinated?

Fully vaccinated people with Delta variant breakthrough infections can spread the virus to others. But the period of time when vaccinated people can spread the virus appears to be shorter, according to the Centers for Disease Control and Prevention. 

Is it still safe for fully vaccinated people to gather unmasked?

The answer depends on any number of variables, including where you are, who you’re with, and your own personal health. Some things to consider are: What’s your community’s transmission rate? How well ventilated is the room you’re in?  Do any of the vaccinated people you’re with have sniffles, a cough or a fever? Do you have any underlying health conditions that make you more vulnerable to complications from COVID-19?

Even in Rhode Island, where 67% of residents are fully vaccinated as of Wednesday, Rhode Island’s transmission rate, driven by the Delta variant, has been what the CDC considers high, at more than 200 cases per 100,000 people in the previous week.

More frequent COVID-19 screening tests, like those being done at Brown University, are one way to reduce the risk of vaccinated people with breakthrough infections spreading the virus.

Will breakthrough infections like those at Brown mean that students are in for another year of eating grab-and-go meals and taking classes on Zoom?

Brown imposed temporary restrictions to prevent more outbreaks. And the college requires that all students, faculty and staff get vaccinated against COVID-19. The breakthrough infections were discovered because Brown has been doing weekly testing. And so far, nobody has become sick. So what happened at Brown is actually evidence that testing and prevention strategies like masking are working. In fact, Brown has announced students can return to in-person dining on Friday.

Should everyone who is fully-vaccinated get tested for COVID-19 regularly, the way some healthcare workers are?

Nationally, COVID-19 testing should be much more widely available on a regular basis to curb the spread of the virus, Kates, of the Kaiser Family Foundation, said. In the U.K. the National Health Service is providing free, rapid COVID-19 tests and advising people to screen every three to four days even if they are vaccinated and asymptomatic.

“If we had the kind of screening tests where everybody was able to screen themselves on at least a weekly or bi-weekly basis,’’ Kates said,  “we’d find so many more infectiousness periods where people could be very careful, and we'd reduce risk to everybody else.’’

If I have no symptoms but I want to get tested for COVID-19, what type of test should I get? 

The PCR test is considered the gold standard for diagnosing SARS-CoV-2. And PCR tests are widely available in Rhode Island, which ranks top in the county for COVID-19 testing per capita, according to the Sept. 20 data compiled by Johns Hopkins University. At state-run test sites in Rhode Island, symptomatic patients will get swabbed twice, first for a rapid antigen test for same-day results, and second for a PCR test that can be sent to a lab for results in one to two days. You can schedule a test online at portal.ri.gov.

The do-it-yourself COVID-19 tests

Antigen tests are less sensitive than the PCR tests for detecting the presence of the virus. However, antigen tests produce results in about 15 minutes, which enable people to isolate before they infect others. The antigen tests may not detect COVID-19 early on, when the virus is incubating, but generally will detect it when the person becomes contagious, which is why they are often referred to as “contagiousness tests,’’ according to RapidTests.org, a blog whose advisors include Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T. H. Chan School of Public Health.

By contrast, a PCR test can detect minute quantities of the coronavirus but that may not mean that the person is still infectious and is therefore at risk of spreading the virus. 

If you’re fully vaccinated, you might want to take an antigen test before you go to a dinner party, or visit with another vaccinated person who has a compromised immune system and is more at risk of severe COVID-19.

The BinaxNOW test, made by Abbott, is available in stores or online and costs about $24 for a two-test kit. Other rapid antigen tests authorized by the federal Food and Drug Administration (FDA) include QuickVue and the Ellume COVID-19 Home Test made by Quidel. (These typically are not covered by insurance.) 

--this story was updated at 1:58 p.m.

Health reporter Lynn Arditi can be reached by email at larditi@thepublicsradio.org. Follow her on Twitter @LynnArditi