Breakthrough COVID-19 Infections: What's the Risk?

In July, Charlie Nieland headed off from New York City to his 40^th high school reunion in Milwaukee, looking forward to a fun — and safe — celebration after over a year of very little socializing. After all, he was fully inoculated against COVID-19, and he assumed most of his classmates would be as well.

When he got back from his four-day weekend of maskless partying, he checked the reunion Facebook page and was surprised to read a post from one alum who revealed that he had tested positive for COVID-19. Because Nieland had received the Johnson & Johnson vaccine, he wasn’t all that worried that he might have become infected at the reunion, but to be on the safe side he got tested.

“I couldn’t believe it,” he says. “I felt I had been doing everything right to avoid getting COVID-19, so when I found out I tested positive, it felt weird. Anecdotally, I had been hearing about more vaccinated people getting these breakthrough cases. And then I was one. I’m not mad, and from what I knew about vaccines, I thought I wouldn’t get super sick.”

Nieland was right. His symptoms were mild — he felt tired, a little dizzy, and somewhat congested. “But it never settled in my chest,” he says. He isolated for the 10 days that the Centers for Disease Control and Prevention (CDD) recommends, his symptoms passed, and he was no longer considered to be contagious.

Stories Are Spreading About Vaccinated People Getting COVID-19

Recently, reports of breakthrough cases like Charlie’s have increasingly appeared in the media. On July 26 the NFL revealed that 13 vaccinated NFL staffers and four vaccinated players had tested positive for COVID-19. Deadline reported in May that comedian Bill Maher cancelled a taping of his talk show after testing positive — he was fully vaccinated and remained asymptomatic.

On August 2, Senator Lindsey Graham announced that he had tested positive despite being vaccinated and had mild symptoms similar to those of a sinus infection. Graham tweeted, “I am very glad I was vaccinated because without vaccination I am certain I would not feel as well as I do now. My symptoms would be far worse.”

Health data analysis by NBC News on July 30 revealed that at least 125,000 fully vaccinated Americans have tested positive for COVID-19 and 1,400 of those have died. While the numbers are significant, these infections are occurring in fewer than 1 percent of the more than 162 million people who have been vaccinated.

The CDC emphasizes that vaccination largely prevents severe illness, hospitalization, and death. Analysis of federal data by the Associated Press on June 29 indicated that about 99 percent of all hospitalizations and deaths are among the unvaccinated.

With about 30 percent of the adult U.S. population yet to receive a COVID-19 vaccine, cases have been rising. The current seven-day moving average of daily new U.S. cases is 66,606 — an increase of 64.1 percent compared with the previous seven-day moving average of 40,597, according to CDC estimates.

Public health officials say that the highly transmissible delta variant (B.1.617.2), which now accounts more than 80 percent of all COVID-19 cases in this country according to the CDC, is fueling the rise in infections, hospitalizations, and deaths.

The CDC just published a study on July 30 demonstrating how the variant may be causing more breakthrough cases. The research detailed how nearly 3 out of 4 people (346 out of 469) who tested positive for COVID-19 in a Massachusetts outbreak were fully vaccinated.

“The big concern is that the delta variant appears to be able to colonize people fairly well, even if they’re vaccinated,” says Julie Parsonnet, MD, an infectious diseases specialist and professor of medicine at Stanford University. “Those people who are vaccinated are then able to transmit it — it certainly happens at a much lower rate than what happens with unvaccinated people, but it is a risk that people who are vaccinated may get mild illness, and they may be able to transmit it to others if they’re not wearing masks.”

Mask-Wearing Makes a Comeback for the Vaccinated

On July 28, the CDC issued revised guidelines to recommend that fully vaccinated people once again wear masks in public indoor settings in areas of substantial or high transmission. The health agency’s COVID Tracker shows that about 80 percent of U.S. counties now fit that description.

“In these communities, vaccine coverage is often lower and cases are surging, placing pressure on healthcare facilities once again,” says Jennifer Horney, PhD, professor of epidemiology and core faculty with the Disaster Research Center at the University of Delaware in Newark.

The revised CDC guidelines also urge the fully vaccinated to get tested within three to five days if they have been exposed to someone with suspected or confirmed COVID-19.

Vaccines Protect But May Be Less Effective in Fighting the Delta Variant

While studies have shown vaccines to provide powerful protection against the delta variant, the available vaccines may be less effective than they were against earlier coronavirus strains.

Research published in The New England Journal of Medicine on July 21 demonstrated that two doses of the Pfizer vaccine had an 88 percent effectiveness rate against the delta variant. A recent report from Israel’s Health Ministry, however, indicated that the Pfizer vaccine is just 39 percent effective in that country, where the delta variant prevails, according to CNBC on July 23. Even so, the Israeli report found that the vaccine still offers a strong defense against hospitalization (88 percent) and severe illness (91 percent).

Some research, such as a preprint study posted to bioRxiv on July 19, has suggested that the Johnson & Johnson vaccine may not be as effective as Pfizer and Moderna shots when it comes to fighting the delta variant. Authors of the investigation in bioRxiv concluded that “the data underscore the importance of surveillance for breakthrough infections that result in severe COVID-19 and suggest the benefit of a second immunization.”

Another paper, published on July 28 in The New England Journal of Medicine, indicated that people who develop breakthrough cases could still have COVID-19 symptoms such as fatigue, brain fog, and shortness of breath even six weeks after diagnosis.

A separate investigation posted July 23 to medRxiv reviewing results from a poll posted to the Survivor Corps Facebook page found that of 1,949 respondents who reported developing COVID-19 after being fully vaccinated, 24 said they experienced ongoing, so-called “long COVID-19” symptoms — although only one had to be hospitalized.

Could Booster Shots Help Prevent Breakthrough Infections?

Public health officials are currently evaluating the potential benefits of booster shots — especially for the immunocompromised who may have more difficulties mounting a strong defense against the virus. Dr. Parsonnet underscores that the majority of serious infections she has seen at Stanford among the vaccinated have been in immunocompromised individuals.

“I feel sorry for a lot of these people who are immunocompromised who are really worried about running into people who are going to infect them,” she says. “It’s tough to feel like you’re this target for the virus.”

The Advisory Committee on Immunization Practices (ACIP), which counsels the CDC, recently came out in favor of booster injections for the immunocompromised (who make up about 2.7 percent of the U.S. adult population), according to The Wall Street Journal on July 22.

At this time, however, the U.S. Department of Health and Human Services says that Americans who have been fully vaccinated do not need a booster shot. “The FDA, CDC, and NIH are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary,” stated the HHS in a July 8 press release. “This process takes into account laboratory data, clinical trial data, and cohort data — which can include data from specific pharmaceutical companies, but does not rely on those data exclusively.”

The bottom line is that all research continues to indicate that the available vaccines substantially reduce the risk of severe illness, hospitalization, and death.

RELATED: 7 Biggest COVID-19 Myths

Vaccines Remain the Best Way to End the Pandemic

“The best way to combat the [delta] variant is to get vaccinated as quickly as possible, as we know this will decrease transmission as well as the possibility for a new variant,” says Teresa Murray Amato, MD, chair of emergency medicine at Long Island Jewish Forest Hills in Queens, New York.

In time, Parsonnet foresees the coronavirus evolving to a point where it requires a once-a-year vaccine, as is the case with influenza.

“I think it’s going to be very much like flu, that we’re going to say, okay, every year you’re going to get your flu-coronavirus vaccine,” says Parsonnet. “Public health experts are going to look at what variants are circulating or that they’re worried are going to be highly prevalent, and they’re going to vaccinate for it.”