How common are serious side effects in COVID-19 treatments?

By Pooja Mamnoor

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    4/21/25 (LAPost.com) — Most approved COVID-19 treatments cause few serious side effects, according to new research from the Keck School of Medicine of the University of Southern California.

The comprehensive analysis evaluated evidence from 54 U.S. studies spanning clinical trials and observational research in inpatient and outpatient settings.

Oral antiviral medications – including Paxlovid – showed no significant association with serious adverse events. These findings offer reassurance to patients who may require COVID-19 treatment, particularly those with risk factors such as advanced age, obesity, cardiovascular issues, diabetes, or compromised immune systems.

“The main message is, if your doctor puts you on Paxlovid, you do not have to worry about serious side effects,” Susanne Hempel, professor of clinical population and public health sciences and director of the Southern California Evidence Review Center, who oversaw the research said. “There are no serious adverse events for any of the oral medications that you are taking at home for COVID-19.”

The research, published in Open Forum Infectious Diseases, examined only studies comparing COVID-19 therapy with standard care, placebo, or no treatment. This methodology allowed researchers to reasonably exclude the effects of the disease itself when assessing treatment safety.

Investigators reached beyond peer-reviewed literature to include data submitted to the Food and Drug Administration and the National Library of Medicine’s clinicaltrials.gov site, providing a more complete safety profile for these treatments.

Monoclonal antibodies that bind to the coronavirus’s spike protein, which were previously administered intravenously in hospitals but are no longer authorized by the FDA due to lack of effectiveness against current variants, were also found to be free of serious adverse events. These included Evusheld and similar treatments.

However, not all COVID-19 therapies demonstrated the same safety profile. In some studies, Actemra, an intravenous monoclonal antibody also known by the generic name tocilizumab, was associated with infection and low white blood cell counts. This medication works differently from other monoclonal antibodies used against COVID-19.

Transfusions of convalescent plasma – a blood product taken from recovered COVID-19 patients – showed the most concerning safety issues. The treatment was linked with a higher risk of internal bleeding, infection, and blood clots.

Margaret Maglione, a project leader at the Evidence Review Center and first author of the study, noted the serious adverse events identified aligned with current product labeling.

“Manufacturers must submit very detailed records to the FDA for emergency authorization, so every adverse event should have been reported,” Maglione said. “We did not identify any serious adverse events that were not already described on the product packaging.”

The study focused exclusively on serious side effects, defined using the National Institutes of Health’s standard five-point scale. Researchers considered only conditions rated three or above, indicating severe conditions requiring hospitalization, with five representing fatal events.

“Given the unique nature of the pandemic and the rapid production of treatments for COVID-19, the findings are very reassuring,” Jeffrey Klausner, professor of clinical population and public health sciences at the Keck School of Medicine, said. “With a severe public health emergency like COVID-19, it is critical that there exists a government compensation program for treatment-related injuries that is based on the best scientific evidence. Now we know with additional certainty, that the treatments are safe without a high frequency of serious side effects.”

The research was conducted to help develop a countermeasure injury compensation table, which determines eligibility for public benefits for patients and families who report adverse events from medical treatments.

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