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.