Summary
On January 14, 2021, a state of emergency was declared in Osaka Prefecture owing to the Coronavirus disease-2019 (COVID-19) pandemic. However, as the number of patients decreased, lifting the state of emergency was proposed. After the emergency declaration was lifted, the number of patients with COVID-19 and severe COVID-19 in Osaka Prefecture increased rapidly. In Osaka Prefecture, the presence of the VOC 202012/01 variant was confirmed on February 22, 2021. As this variant contributes to a higher risk of death than the conventional strains, this study investigated change in the age range of patients with severe COVID-19, in Osaka with a rapidly growing population before and after the emergency declaration. The study included two periods: December 14, 2020, to January 13, 2021 (Period A: before the declaration) and March 8, 2021, to April 7, 2021 (Period B: after the declaration). Data were collected and analyzed to compare the proportions of severely ill COVID-19 patients in different age ranges and the presence or absence of primary illnesses in them between Periods A and B. The results showed that a higher proportion of younger individuals (aged <60 years) in Osaka had severe COVID-19 in Period B than in Period A. We must be more diligent in implementing infection control measures than before. Any change in infectivity and severity should be monitored in patients infected with VOC 202012/01 and conventional severe acute respiratory syndrome-Coronavirus-2 in Osaka.
Introduction
In Osaka Prefecture, the government declared a state of emergency on January 14, 2021. This emergency declaration was scheduled to last until March 7. However, as the daily number of patients with Coronavirus disease-2019 (COVID-19) began decreasing, the Osaka government decided to lift the declaration before the announced date[1]. Consequently, the emergency declaration in Osaka Prefecture ended on March 1. Despite lifting the declaration, restaurants in the center of Osaka continued to operate for short business hours. However, the number of patients-especially, that of critically ill patients-in Osaka Prefecture increased again, leading to a sharp increase in the use of critical care beds for the hospitalization of patients with severe COVID-19[2]. In response, the government of Osaka Prefecture imposed a declaration of medical emergency on April 8, 2021[3].
In Osaka Prefecture, a British mutant strain (VOC 202012/01) was identified for the first time on February 22, 2021; this variant has a higher effective reproduction number[4] and is associated with a higher risk of death[5, 6] than the conventional strains. Among patients with COVID-19, the proportion of patients infected with VOC 202012/01 in Osaka Prefecture was nearly 70%[7], which may be related to the rapid increase in the number of infected and severely ill patients. Owing to the spread of VOC 202012/01, a highly infectious variant that confers a high risk of death, it is possible that the proportion of critically ill patients in Osaka is different than before, in terms of age and the presence or absence of primary illnesses. This study investigated changes in the age groups of critically ill patients and the presence or absence of primary diseases during the 31 days before the declaration of a state of emergency before VOC 202012/01 was discovered in Osaka Prefecture and during the 31 days after the declaration of a state of emergency after VOC 202012/01 was discovered.
This descriptive epidemiological study used publicly available surveillance data[2]. The press release dataset was scanned for all reported patients with severe COVID-19 in Osaka. Ventilator use, extracorporeal membrane oxygenation use, tracheal intubation, and intensive care unit admission indicated that patients were severely ill. From these data, the age of critically ill patients and presence of primary illnesses were noted. Data on patients with severe COVID-19 during the 31 days before (December 14, 2020, to January 13, 2021; Period A) and after (March 8, 2021, to April 7, 2021; Period B) the emergency declaration were collected. The chi-square test was used to determine differences in the proportions of severely ill patients with COVID-19 in different age ranges and the presence or absence of primary illnesses in them between Periods A and B. During these periods, the healthcare system was considerably strained owing to an increased number of infected and severely ill patients.
In total, 317 and 226 patients with severe COVID-19 were reported in Periods A and B, respectively. The distribution of severe patients based on age, sex, and the presence or absence of primary illnesses is shown in Table 1. Males accounted for 68.7% of all patients in Period A and 72.6% in Period B. In both periods, the highest number of severely ill patients was within the age range of 70-79 years. The number of severely ill patients aged <60 years[8], who were considered to be at a relatively low risk of severe disease in previous studies, was higher in Period B than in Period A.
In severely ill patients reported in Periods A and B, differences were noted between the proportions of patients with and without primary illnesses as well as between the proportions of severely ill patients aged ≥60 years and <60 years. The results showed that Period A had a significantly higher percentage of critically ill patients without any primary illness than Period B (p<0.001). The proportion of patients aged <60 years was significantly higher in Period B than in Period A (p=0.004). The proportion of severely ill patients aged 20-59 years with no primary illness was higher in Period B than in Period A. This finding may suggest that the spread of VOC 202012/01 has further increased the risk of severe disease in those with primary illnesses and those aged <60 years.
VOC 202012/01 is more infectious than the conventional severe acute respiratory syndrome-Coronavirus-2 (SARS-CoV-2) strains, and several studies have shown a higher mortality rate in patients infected with VOC 202012/01[4-6]. However, some studies have shown the opposite[9, 10], and opinions have been divided. This descriptive analysis was too simplistic to conclusively determine a causal relationship between VOC 202012/01 and the chronological change in the number of severely ill patients in Osaka. However, it showed that the number of severely ill patients aged <60 years is currently increasing in Osaka Prefecture. Therefore, we must be more diligent in implementing infection prevention measures than before. In future, patients infected with VOC 202012/01 and conventional SARS-CoV-2 in Osaka should be monitored to check for possible changes in infectivity and severity.
Ethics
Peer-review: Externally peer-reviewed.
Financial Disclosure: The author declared that this study received no financial support.