The COVID-19 epidemic began at the end of 2019, and by June 2023, 760 million people had been affected and 6.9 million had died. Although the rate of severe cases has decreased since the Omicron variant became predominant [1], long COVID is still one of the unresolved issues.

Symptoms may persist for several months after infection with COVID-19 and are commonly referred to as long COVID, post-acute COVID-19 syndrome or post-COVID-19 condition [2,3]. Long COVID is characterized by a variety of symptoms across organ systems, including fatigue, shortness of breath, and cognitive dysfunction, often with fluctuating periods of wellness followed by relapse. Long COVID is reported to be experienced by one in five to seven people infected with SARS-CoV-2 [4,5], although the frequency is thought to be decreasing because the Omicron variant has become predominant [6]. In Japan, there have been no large-scale cohort studies on long COVID, and the actual status of long COVID, especially after the Omicron variant, is not well understood.

Since the advent of COVID-19, various clinical studies have been conducted using mobile applications. For example, the ZOE Health Study in the United Kingdom utilizes mobile applications to estimate the number of new COVID-19 cases, evaluate the effectiveness of the COVID-19 vaccine, and survey the actual status of long COVID [7]. By utilizing mobile applications in this manner, the health status of patients with infection can be continuously investigated without requiring outpatient visits. We conducted the first study on long COVID utilizing a mobile application in Japan, and report the results herein.