A carefully designed trial has delivered a disappointing but important answer for the millions living with long Covid: an extended course of the antiviral Paxlovid did not help.
One leading theory of long Covid is that lingering, persistent virus keeps driving symptoms — which suggested that a longer antiviral course might clear it and bring relief. To test that, researchers at Mass General Brigham ran a randomized, placebo-controlled trial with three arms — the full Paxlovid combination, each of its two components (nirmatrelvir and ritonavir) alone, and placebo — using extended 15-to-25-day courses, far longer than the standard 5-day acute-Covid regimen. The findings were published in The Lancet Infectious Diseases and funded by the NIH.
The result
“Unfortunately, treating viral persistence with this antiviral medication did not show evidence of clinical benefit,” said co-principal investigator Lindsey Baden. In other words, a longer Paxlovid course didn’t improve long-Covid symptoms compared with placebo.
Why it matters
Negative results like this are genuinely useful: they help steer patients and researchers away from ineffective options and toward more promising ones. The finding doesn’t rule out that viral persistence contributes to long Covid in some people — but it suggests that this particular antiviral, even at extended doses, isn’t the answer. Long Covid remains an urgent, still-unsolved problem, and rigorous trials like this one are how the field narrows the search for treatments that actually work.