Nearly 3% of medical workers in a new Israeli study contracted COVID-19 even though they were vaccinated, and 19% of them still had symptoms six weeks later.
Although the vaccines were never expected to be perfect, the findings raise questions about their protection and suggest that even vaccinated people could experience long-term symptoms such as such as fatigue, brain fog and shortness of breath.
Dr. Ashish Jha, dean of the Brown University School of Public Health, said he finds it concerning – though not conclusive – that people had lingering symptoms weeks after getting sick.
"There really may be a risk here, but we don't know how big a risk and how much of a problem it is," he said.
Most of the people in the study who got sick had mild symptoms, and none were hospitalized.
But Jha said he was troubled that young, healthy people would get so-called breakthrough infections within a few months of vaccination. Scientists expected protection to wane over time, and they expected the vaccines to be less effective among older people and those with pre-existing health conditions.
But that's not who got sick in this study.
Dr. Monica Gandhi, an infectious disease specialist at the University of California, San Francisco, said she's not surprised that a number of health care workers would become infected after being vaccinated because they're constantly exposed to sick people.
"It makes sense to me that health care workers would be particularly susceptible to breakthrough infections," she said via email, "making mitigation procedures (universal masking) even more important in health care settings."
The good news is that none of the 39 people who got infected passed the coronavirus on to anyone else, according to the study, published Wednesday in the New England Journal of Medicine.
Coronavirus vaccines were never designed to perfectly protect people against all infections, noted Dr. Eric Topol, a cardiologist who founded and directs the Scripps Research Translational Institute in California.
He said current vaccines are great at preventing serious infection deep in the lungs, but not at blocking infection in the upper airways. What's needed, he said, is a nasal-spray vaccine that would stop the coronavirus from taking hold at all.
Topol said he wishes the federal government had prioritized a nasal vaccine along with shots.
"It would have been the perfect combination," he said.
Some researchers believed vaccines would reduce viral loads, and people with lower viral loads would be less likely to have lingering symptoms. Topol said the new study brings that into question.
"Those who are vaccinated did everything right, but some are going to go on to long-COVID, and that's really unfortunate," he said.
The study followed about 1,500 Israeli health care workers for four months after they received the Pfizer-BioNTech vaccine. Anyone who tested positive more than 11 days after the second dose was considered a breakthrough case.
Thirty-nine people – 2.6% of the total – were diagnosed with the virus. One was immunosuppressed; the rest were healthy, including nurses, maintenance workers and a few doctors.
All 37 people for whom data was available were infected by an unvaccinated person, usually within their homes.
Two-thirds had mild symptoms; the rest had none at all.
Six weeks after their diagnosis, 19% reported they still had at least one symptom: loss of smell, cough, fatigue, weakness, difficulty breathing, or muscle pain. Nine employees – 23% – weren't healthy enough to return to work after 10 days of required quarantine. One hadn't gone back after six weeks.
Most had the alpha variant of the virus, which is more contagious than the original version, but less infectious than the delta variant that now accounts for most cases in the United States.
Whether delta is more dangerous in addition to being more contagious remains unclear, Jha said.
"The evidence really, really is mixed on whether delta is more virulent," he said. "I can point you to some studies that argue that it is and other studies that argue that it isn't, but none of them are particularly definitive."
Topol said the best protection is to get vaccinated and practice social measures like wearing a mask.
"Don't take the delta stress test. Keep a mask on," he said. "With the vaccine, you can be confident, but you can't be 100% confident."
Contact Karen Weintraub at firstname.lastname@example.org.
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This article originally appeared on USA TODAY: Breakthrough COVID-19 infections can lead to long-term symptoms: study