In rare cases, coronavirus vaccines may cause Long Covid–like symptoms

In late 2020, Brianne Dressen began to spend hours in online communities for people with Long Covid, a chronic, disabling syndrome that can follow a bout with the virus. “For months, I just lurked there,” says Dressen, a former preschool teacher in Saratoga Springs, Utah, “reviewing post after post of symptoms that were just like my own.”

Dressen had never had COVID-19. But that November, she’d received a dose of AstraZeneca’s vaccine as a volunteer in a clinical trial. By that evening, her vision blurred and sound became distorted—“I felt like I had two seashells on my ears,” she says. Her symptoms rapidly worsened and multiplied, ultimately including heart rate fluctuations, severe muscle weakness, and what she describes as debilitating internal electric shocks.

A doctor diagnosed her with anxiety. Her husband, Brian Dressen, a chemist, began to comb the scientific literature, desperate to help his wife, a former rock climber who now spent most of her time in a darkened room, unable to brush her teeth or tolerate her young children’s touch.

As time passed, the Dressens found other people who had experienced serious, long-lasting health problems after a COVID-19 vaccine, regardless of the manufacturer. By January 2021, researchers at the National Institutes of Health (NIH) began to hear about such reports and sought to learn more, bringing Brianne Dressen and other affected people to the agency’s headquarters for testing and sometimes treatment.

The research was small in scale and drew no conclusions about whether or how vaccines may have caused rare, lasting health problems. The patients had “temporal associations” between vaccination and their faltering health, says Avindra Nath, clinical director at the National Institute of Neurological Disorders and Stroke (NINDS), who has been leading the NIH efforts. But “an etiological association? I don’t know.” In other words, he does not know whether vaccination directly caused the subsequent health problems.

NIH’s communications with patients faded by late 2021, though Nath says the work continues behind the scenes. The pullback caused bewilderment and dismay among patients who spoke with Science, who said the NIH researchers were the only ones helping them. Now, a small number of other researchers worldwide is beginning to study whether the biology of Long Covid, itself still poorly understood, overlaps with the mysterious mechanisms driving certain postvaccine side effects.

More discrete side effects connected to COVID-19 vaccines have been recognized, including a rare but severe clotting disorder that occurs after the AstraZeneca and Johnson & Johnson vaccines and heart inflammation, documented after the messenger RNA (mRNA) vaccines manufactured by Pfizer and Moderna. Probing possible side effects presents a dilemma to researchers: They risk fomenting rejection of vaccines that are generally safe, effective, and crucial to saving lives. “You have to be very careful” before tying COVID-19 vaccines to complications, Nath cautions. “You can make the wrong conclusion. … The implications are huge.” And complex and lingering symptoms like Dressen’s are even more difficult to study because patients can lack a clear diagnosis.

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