Study: Paxlovid’s Impact on Vaccinated Seniors May Be Limited

Many people have become skilled at managing COVID-19 through vaccinations, previous infections, at-home tests, and antiviral drugs like .

However, a recent study suggests that Paxlovid might not be as beneficial as previously believed, especially for vaccinated older adults.

In a study published in JAMA on Feb. 20, Dr. John Mafi and his colleagues at UCLA analyzed Canadian data to determine the effects of Paxlovid. Due to a 2022 Canadian health policy that restricted Paxlovid prescriptions to symptomatic individuals around age 70 to prioritize its use for those at highest risk, researchers were able to compare outcomes between those who took Paxlovid and those who did not within this age group, as older individuals face a greater risk of COVID-19 complications.

The study, involving nearly 1.5 million participants, revealed that hospitalization or death rates from COVID-19 were not significantly different between those who received Paxlovid and those who did not. The majority of participants had been vaccinated.

According to Dr. Mafi, the study’s lead author, “Our main finding was that among vaccinated older adults, Paxlovid showed no statistically significant reduction in COVID-19 hospitalizations or on mortality.”

This contrasts sharply with initial findings from Pfizer, Paxlovid’s manufacturer, which indicated an 89% reduction in COVID-19-related hospitalizations and deaths compared to a placebo group. However, the Pfizer study primarily involved middle-aged, unvaccinated individuals, a demographic significantly different from today’s population. Mafi notes, “Yet that 2022 Pfizer study was and continues to be used to support the assumption that the benefits of Paxlovid in unvaccinated adults also apply to vaccinated adults. That’s what is being used to justify its perceived effectiveness—and its list price at $1,650 per treatment course.”

Pfizer responded with a statement that they could not comment on studies they weren’t involved in, but “remain[s] confident in Paxlovid’s clinical effectiveness at preventing severe outcomes, including hospitalization and death, from COVID-19 in patients at high risk of severe illness.”

Paxlovid is intended for individuals at high risk of COVID-19 complications, such as the elderly, immunocompromised individuals, and those with multiple underlying health conditions. This remains the primary criterion for prescribing the medication, now available to anyone 12 or older at high risk of severe disease.

Mafi emphasizes that there is limited data on Paxlovid’s impact on vaccinated individuals, suggesting the benefits are about four times less than reported by Pfizer.

Mafi clarifies, “We are not saying that Paxlovid is useless. What this research is saying is that its effectiveness in older groups who are most vulnerable to COVID-19, but who are vaccinated, is far lower than what the earlier evidence from unvaccinated groups showed.”

While more research is necessary, doctors can use this information when deciding whether to recommend Paxlovid. Other key considerations include a patient’s medical history, the drug’s potential for mild , and , where individuals test positive again after a negative result.

Dr. Katherine Kahn, a distinguished professor of medicine at UCLA and the study’s senior author, plans to discuss these findings with her patients. “For generally health people, I’m not encouraging or discouraging [Paxlovid] if they meet the criteria for taking it,” she says. “But for people with higher risk of morbidity or mortality, we’re more likely to say we might consider [Paxlovid] at this time, even though we don’t know 100% if you will benefit.”

The study highlights the need for further investigation, particularly regarding the influence of prior infections on Paxlovid’s effectiveness. Mafi and Kahn also mentioned limitations in assessing participants’ vaccination history and confirming timely Paxlovid administration within five days of symptom onset. However, they are planning a more detailed analysis of individual-level data to explore other factors affecting the drug’s ability to reduce hospitalizations and deaths.

Kahn concludes, “One of the conclusions of this study is the recommendation for more studies, of both older individuals and those who are vaccinated, of the effectiveness of Paxlovid.”

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