Introduction
The rapid development of therapeutics and preventive strategies for
COVID-19 has occurred during the worldwide
pandemic[1,2]. While vaccines can effectively
prevent severe illness caused by COVID-19, the immune response they
trigger may diminish over time and become less effective against
emerging variants. This highlights the importance of antiviral therapies
for SARS-CoV-2 infection.
Comprising two antiviral protease inhibitors, nirmatrelvir-ritonavir
stands out as a highly potent medication for combating SARS-CoV-2.
Nirmatrelvir, an oral antiviral medication, hinders the replication of
viruses by focusing on the primary protease (Mpro) of
SARS-CoV-2[3]. Nirmatrelvir exhibits comparable
effectiveness against both the original SARS-CoV-2 strain and its
subsequent variants due to the highly preserved sequence of Mpro in
coronaviruses. The plasma concentrations of nirmatrelvir are elevated
due to ritonavir’s inhibition of CYP3A-mediated metabolism. Therefore,
combining nirmatrelvir and ritonavir may maximize the therapeutic
benefit[3, 9]. In the recent EPIC-HR study
published by Hammond et al. (2022), patients with mild to moderate
COVID-19 who were susceptible to developing severe illness within 5 days
of experiencing symptoms were administered
nirmatrelvir-ritonavir. As a result,
they demonstrated a reduced likelihood of hospitalization or succumbing
to the disease. Following this randomized
trial[10], numerous countries have granted
emergency use authorization to nirmatrelvir-ritonavir for the management
of COVID-19.
Medical service providers in China
are responsible for monitoring or treating high-risk COVID-19 patients.
From March, 2022[11], nirmatrelvir-ritonavir has
been one of the few treatment choices that were accessible for
prescription locally. In the EPIC-HR study[10],
the examined groups were comparatively youthful, with obesity being the
most frequently cited risk factor for progressing to severe illness. In
China and many other countries such as Australia, the majority of
COVID-19 patients at high risk are elderly individuals who have various
underlying comorbidities including hypertension, diabetes, and
cardiovascular diseases. The purpose of this study was to evaluate the
effectiveness of nirmatrelvir-ritonavir in the elderly population in
real-world scenarios, and provide guidance for clinical and policy
decision-making.