A new UCLA-led study casts doubt on the efficacy of Paxlovid in reducing COVID-19 hospitalizations and deaths among vaccinated older adults. This research challenges the assumption that Paxlovid, which demonstrated reduced hospitalization rates in unvaccinated middle-aged individuals in a 2022 Pfizer clinical trial, would have similar benefits for their vaccinated counterparts.
Following the 2024 clinical trial, which failed to show any significant reduction in COVID-19-related outcomes among vaccinated middle-aged adults, questions arose about Paxlovid’s impact on older populations. The majority of elderly Americans are already fully vaccinated, making this a crucial area for further investigation.
“Given that advanced age is the strongest predictor of severe COVID-19 cases,” Dr. John Mafi stated, “it was vital to understand if Pfizer’s 2022 trial results could be extended to older and vaccinated populations.” As lead author of the study published in JAMA, he added, “Our findings conclusively rule out significant reductions in hospitalizations due to Paxlovid among vaccinated seniors. While a slight effect cannot be entirely ruled out, it is approximately four times less effective than initially reported.
Dr. Katherine Kahn, senior author and distinguished professor of medicine at the David Geffen School of Medicine at UCLA, emphasized that these results highlight the need for further randomized clinical trials to explore Paxlovid’s impact on high-risk groups such as frail or immunocompromised older adults.
The researchers utilized a natural experiment in Ontario, Canada. The province implemented an age-restricted policy limiting access to Paxlovid only for symptomatic COVID-19 patients aged 70 and above, with exceptions for those who were immunocompromised or had additional risk factors. This led to a significant increase of over 118% in the prescription rate at age 70 compared to just below it.
Despite this substantial rise in Paxlovid prescriptions, there was no notable improvement in COVID-19-related hospitalizations, all-cause hospitalizations, or mortality rates among highly vaccinated older Ontarians. This suggests that access restrictions did not diminish the overall health outcomes of those who were able to receive the medication.
“Our study effectively bypassed a common issue in observational research known as unobserved confounding,” Sitaram Vangala, co-author and biostatistician at UCLA’s Department of Medicine Statistics Core, explained. “By focusing on individuals just below or above the age 70 cutoff for Paxlovid access, we aimed to mitigate any bias that could arise from differences in factors outside our control.”
The study has limitations due to a lack of individual-level data regarding symptoms, timing of previous vaccinations, receipt of Paxlovid treatments, and adherence. However, it provides valuable insights into the efficacy of this medication among vaccinated older adults.
