Why lawmakers tested positive for COVID-19 after Capitol riot, despite vaccinations

Despite receiving one or two doses of a coronavirus vaccine, multiple members of Congress have tested positive for COVID-19 since the riot at the U.S. Capitol.

While currently available vaccines are highly effective against symptomatic illness, it takes about two weeks after the second dose to offer that high degree of protection, according to infectious disease experts. With some lawmakers exposed shortly after their first or second shot, those experts say it's not surprising they became infected after what's being described as a "superspreader" event.

Reps. Bonnie Watson Coleman (D-N.J.), Adriano Espaillat (D-N.Y.), Chuck Fleischmann (R-Tenn.), Pramila Jayapal (D-Wash.), Brad Schneider (D-Ill.) and Lou Correa (D-Calif.) have all reported positive test results since Jan. 6.

It is impossible to know exactly when and where these members of Congress became infected, especially since somebody can pick up the virus up to 14 days before getting a positive test. However, experts say that day at the Capitol was likely very risky for viral transmission.

Dr. Simone Wildes, infectious disease physician and ABC News contributor, described the day as “the classic situation that we tell everyone to avoid .... a small space with a lot of people, poor ventilation, not wearing masks."

"We think of that kind of like a superspreader event," Wildes said.

Some of these lawmakers are now blaming their co-workers for risky exposure during the riot, reporting that they sheltered in rooms with multiple Republican lawmakers who refused to wear a mask. Video of lawmakers, some without masks and standing close together as they sheltered together during the events of Jan. 6, was posted by Punchbowl News. In the video, some members of Congress, including Rep. Markwayne Mullin, were seen refusing to accept a mask when offered.

The attending physician for Congress, Dr. Brian Monahan, notified all lawmakers about possible virus exposure and recommended that each person there that day get tested.

Many lawmakers who tested positive after Jan. 6 had already received one or two doses of the COVID-19 vaccine. However, this doesn’t guarantee them complete protection, especially if in a very risky situation.

Coleman, Jayapal and Schneider had only received one of the two required doses of the COVID-19 vaccine. After receiving one dose of the vaccine, research from the experimental trials published in the New England Journal of Medicine indicates a person is likely only about 50% protected.

Espaillat had received both doses of the vaccine. He reported getting the second dose the same week as the riot. Once someone gets their second dose of the vaccine, it takes time for immunity to develop. The Moderna vaccine reaches 94% effectiveness two weeks after the second dose, and the Pfizer vaccine reaches 95% effectiveness one week after the second dose.

“I received the second dose of the #COVID19vaccine last week and understand the [effects] take time," Espaillat wrote on his Twitter. "I have continued to be tested regularly, wear my mask and follow the recommended guidelines”.

If Espaillat was exposed to the virus on Jan. 6 and had received his second dose of the vaccine that same week, he may not yet have had maximum protection.

Wildes emphasized that even people who are fully vaccinated with both doses are still potentially at risk of contracting the virus. The vaccines are roughly 95% effective, according to the companies, meaning that about 5% of people who get the vaccine may still develop symptomatic disease after being exposed. Also, other groups of people, like those who are immunocompromised, may not develop as much immunity.

“We do get prevention when we get the vaccine, but it’s not 100%," Wildes said. She also pointed out that some things are still unknown. For example, the large clinical trials demonstrating the vaccines' effectiveness only tested to see if the vaccines work to prevent COVID-19 illness with visible symptoms, like coughing, sneezing or fever.

But approximately 59% of COVID-19 transmission comes from people who have no symptoms, according to a study by CDC researchers published in JAMA Network Open, and scientists still don't have a solid understanding of how effectively the vaccine blocks asymptomatic illness.

That means, potentially, "you could still harbor the virus and possibly spread it to others," Wildes said.

This is why public health experts say that even after both shots, people need to keep wearing masks and staying socially distanced until science offers better answers about asymptomatic transmission after vaccination.

“Even though you have been vaccinated, that doesn’t mean you should drop your guard," Wildes said.

Rose Marie Leslie, M.D., is a chief family medicine resident at the University of Minnesota Medical School and a contributor to the ABC News Medical Unit.