Recent research published in JAMA indicates that Paxlovid, the oral antiviral medication authorized for treating severe COVID-19 symptoms, may not significantly reduce the likelihood of hospitalizations or fatalities among older vaccinated adults in Canada.

The authors highlighted that Pfizer’s original clinical trials were conducted on unvaccinated individuals, with median ages ranging from 42 to 46. Since older adults are more frequently vaccinated against COVID-19 and face a higher risk of severe health complications from the virus, this presents a crucial distinction.

The study assessed overall mortality and hospitalization rates among adults in Ontario, Canada. Between April 1 and November 30, 2022, an age-restricted policy allowed only those aged 70 and above to access Paxlovid.

“Given that advanced age is the most significant predictor of severe COVID-19, it has been essential to explore whether Pfizer’s trial results apply to older, vaccinated populations,” stated Dr. John Mafi, the lead author of the study, in a press release from the University of California, Los Angeles.

The researchers examined the outcomes of adults just under 70 who were not given Paxlovid compared to those who received the treatment. Their analysis included 1,620,884 Ontarians aged 65 to 74 during the study timeframe, with 87.5% of participants having received at least two COVID-19 vaccinations.

Weaker Impact of Paxlovid Compared to Clinical Trials

Overall, the prescription rate of Paxlovid surged by over 118% following the implementation of the age-based policy, particularly among those aged 70 and older.

However, this increase did not lead to a reduction in either hospitalizations or deaths for the patients treated with the antiviral.

Comparing individuals just below and just above 70 years old revealed no significant differences in COVID-19-related hospitalizations (39.5 vs. 42.9 per 10,000 patients per month) or overall mortality rates (109.6 vs. 115.7).

The findings indicated that Paxlovid’s effectiveness on COVID-19 hospitalizations among vaccinated older adults is four times less potent than what was reported in Pfizer’s 2022 clinical trial, showing only a 1.3 percentage point reduction in hospitalizations. The original study reported an absolute risk reduction of 5.5 percentage points.

“As the study revealed no significant impact on COVID-19 hospitalizations and deaths among vaccinated older adults, our results highlight the critical need for additional randomized clinical trials to investigate Paxlovid’s efficacy in high-risk populations, including older individuals who are frail or immunosuppressed,” emphasized Dr. Katherine Kahn, another author of the study.