As the delta variant makes a deadly sweep through unvaccinated communities, renewing calls for masks and vaccine mandates, health experts say that rare “breakthrough infections” among vaccinated people are not a sign that vaccines are failing. Instead, they are a warning of how vaccine holdouts can endanger even their inoculated neighbors.
The amount of breakthrough cases we’re seeing actually suggest that the vaccines “are still working great,” but too much is being asked of them, said Dr. Drew Weissman, who spent nearly two decades conducting research that led to the development of the mRNA vaccines manufactured by Pfizer and Moderna to stop the coronavirus.
Mounting research suggests the variants are placing greater strain on the vaccines. When people are infected with the delta variant, Huffman said they produce a thousand times greater viral load than seen from the original COVID-19 strain. That means the delta variant is more efficient at spreading and every time an infected person coughs, sneezes or speaks, they potentially release much more of the virus — and opportunities to get someone else sick — than earlier in the pandemic.
With only about half of the nation’s population — 163.3 million people — fully vaccinated against the coronavirus, the vaccine’s advantages begin to erode, said Weissman, a physician and infectious disease expert at the University of Pennsylvania. And in some pockets of the country, fewer than a third of people have received full vaccine protection.
“You can’t control a pandemic when 30 percent or even half the people are immunized,” he said.
It’s important to remember that occasional breakthroughs are expected with any vaccine. Getting vaccinated against the virus is a lot like applying sunscreen while vacationing at the beach, said Dr. Alex Huffman, an aerosol scientist and professor at the University of Denver. Sunscreen provides some protection against sunburn, but a cautious person might also wear a wide-brimmed hat or avoid sitting out during the height of the day. For COVID, face masks and social distancing, particularly at indoor public places, could be similarly useful in situations where there is higher risk, he said.
A substantial portion of people in the U.S. have been exposed to misinformation about the safety and effectiveness of COVID-19 vaccines — including that breakthrough infections somehow mean that they do not work –obscuring how they and others perceive those risks, experts say.
Ann Marshall, a nurse practitioner and mother of two in Minnetonka, Minnesota, eagerly received her first dose of Pfizer’s COVID-19 vaccine in February.
In the months before, she regularly submitted to nasal swab tests to ensure she posed no risk of infecting others, had tended to her 9-year-old daughter when she came down with the virus, and faithfully masked up when out in public. When her state relaxed mask restrictions in early July, she said she went maskless to the grocery store once, exercised at her gym twice, picked her kids from day camp and worked a few hours in her clinic.
And then Marshall developed light chest congestion and body aches. She tempered her fever with ibuprofen and could not smell the brownies her daughter baked or taste the burger her husband grilled. Two days later, she was diagnosed with COVID-19 for the first time since the pandemic started.
Marshall said she felt “that maybe we stopped wearing masks a little too soon.”
Marshall’s concern is shared by several public health experts, including Dr. Leana Wen, who said she was confused on May 13 when the Centers for Disease Control and Prevention lifted mask mandates for fully vaccinated people, easing social pressure on unvaccinated people and placing the country on the “honor system.”
“We don’t trust the honor system,” said Wen, an emergency physician and public health professor at George Washington University and a former public health commissioner for Baltimore. “The unvaccinated are now putting the vaccinated at risk.”
What we know — and don’t know — about breakthrough infections
When scientists developed vaccines to slow the spread of the coronavirus pandemic, their vaccine candidates were judged effective based on whether or not people were hospitalized or died after getting immunized.
Even with delta, almost everyone who dies from COVID-19 — 99.5 percent of known cases — are unvaccinated people, along with 97 percent of people hospitalized for the illness. That suggests that the vaccines are still highly effective, said U.S. Surgeon General and Dr. Vivek Murthy during a recent press briefing.
The CDC is counting vaccinated people who have been hospitalized or died from the coronavirus. Based on data available so far, that very rarely happens.
In a study published July 28 in the New England Journal of Medicine, researchers analyzed results from nasal swab tests collected from 1,497 fully vaccinated health care workers at Israel’s largest medical center, with the last tests gathered by April 28, when the alpha variant was taking hold in Israel. They found 39 breakthrough infections. Those who were infected presented with mild symptoms, if any at all, the study authors wrote. And these results were finalized months before the delta variant dominated the pandemic. In a July 21 study published in the same journal, researchers noted there were “only modest differences in vaccine effectiveness” between people exposed to the alpha variant versus the delta variant.
But in the U.S., no one knows exactly how many breakthrough cases there really are because nationwide data doesn’t exist. The agency does not count vaccinated people who have been diagnosed with the disease but are asymptomatic or have only mild symptoms, said Dr. Ashish Jha, dean of Brown University’s School of Public Health. That’s problematic, he said, because the way researchers count infections among vaccinated people is vital to investigating this continually evolving virus, he said.
“One of the most critical questions is how much forward-transmission is happening from breakthrough infections,” Jha said. “That’s something I don’t feel like we have a good grip on and is absolutely essential to understand.”
These are really important questions, and it is really difficult to answer them without data, Wen said, who added that, “we need to understand what we’re dealing with here.”
The risk of a breakthrough infection for vaccinated people with symptoms upon exposure to the delta variant is reduced by seven-fold and that reduction is 20-fold for hospitalizations and death, Dr. Rochelle Walensky, who directs the CDC, said Tuesday.
However, the CDC does track cohorts of fully vaccinated essential workers, including those in the health care and long-term care industries, to better understand how protective vaccines are. Dr. Anthony Fauci, the White House’s chief medical advisor, told PBS NewsHour anchor Judy Woodruff on Tuesday that, from those cohorts, they are seeing data showing that fully vaccinated people who get infected “clearly can transmit it to other people.”
What people misunderstand about breakthrough infections
Dr. Jennifer Nuzzo, an epidemiologist and professor at the Johns Hopkins School of Public Health, said that CDC’s decision to track only severe COVID-19 cases among fully vaccinated people is reasonable because it tells us whether the vaccines are working as designed.
Vaccines don’t supercharge one’s immune system so that it zaps the virus before any symptoms develop. And testing positive after being exposed to the virus does not mean your vaccine failed, she said. You could still test positive while your immune system is building its response, which could result in blunted symptoms, if any at all.
“We have unrealistic expectations for what a vaccine can do,” she said.
She discouraged organizations — like pro baseball teams — from doing surveillance testing among vaccinated people without symptoms, saying “it probably does more harm than good” in eroding public confidence.
When the chance of dying from COVID-19 is about one in 200 for an unvaccinated person, while the chance of adverse events from an mRNA vaccine is about 2 to 4 per million, Weissman said the choice is clear. It bothers him “to no end,” he said, when he hears of patients who ask to be vaccinated against COVID-19 when they are already infected and moments before they are intubated: “They could have taken the vaccine a month earlier and not ended up in this position.”
In this moment, when there’s public confusion around fully vaccinated people getting sick with the virus, some Republican lawmakers, such as Texas Sen. Ted Cruz, have suggested that moves to mandate masks could further undermine confidence among the unvaccinated.
Fauci said the solution was not to avoid mandates but for Republican leaders to promote vaccination. He pointed to Arkansas’ Republican Gov. Asa Hutchinson, who has traveled across his state in a series of community chats to answer people’s questions about the vaccines and encourage more people to get immunized as hospitals fend off a surge in cases.
“We would not be in this situation if we already had now the overwhelming proportion of the population vaccinated,” he said.
In the meantime, back to masks?
For people who are vaccinated and wondering how safe they are, Nuzzo said they have to weigh their personal risks and make choices, based especially on where they are living. On Tuesday, the CDC updated its guidance on masks, saying fully vaccinated people should wear them indoors when they live in areas with substantial or high transmission, i.e. 50 new cases per 100,000 people over the last week. And the agency said everyone in schools should mask up this fall. The Biden administration also announced plans to require federal workers to be vaccinated to work in person or test regularly for infection.
In recent weeks, Huffman, who has studied how COVID-19 has spread through people simply breathing and talking, was trying to convince his child’s school principal that students, teachers and staff should wear masks when in-person classes resume. The principal told Huffman that he would follow whatever the CDC recommended. When the federal agency advised schools to adopt universal masking policies, Huffman was elated.
“Masks are a really big piece of the public health puzzle still,” Huffman said.
Less than a week after her diagnosis, Marshall said she is beginning to feel better and has started to resume some housework. But she said if could do things over again, she would “wear a mask.”
She said she doesn’t worry so much about herself. “I wasn’t going to end up in the hospital. I knew I wasn’t going to end up dying from this because I had been vaccinated,” she said. “But for me to know that I could potentially — now that I have it — I could spread it to somebody who might end up in the hospital.”
Without more people getting vaccinated or taking precautions to slow the pandemic’s rising momentum, especially in places with surging cases, the progress made against the coronavirus could slip away, creating conditions that invite the virus to evolve further. Walensky said warned, “The big concern is that the next variant that might emerge — just a few mutations potentially away — could potentially evade our vaccines.”.
That means that people who are fully vaccinated should still be cautious, avoiding crowds and continuing to do “all the things that help” to prevent new infections, said Dr. Eric Topol, a cardiologist, scientist and author who founded and directs the Scripps Research Translational Institute.
“You got your vaccine — you’re great,” Topol said. “Don’t give it a stress test.”