Development of the coronavirus disease 2019 (COVID-19) vaccine has been key to countering the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite the current endemic status of COVID-19, patients with comorbidities and older adults remain vulnerable to severe illness and death due to COVID-19 infection. Therefore, medical agencies and organizations worldwide recommend COVID-19 vaccination, especially for individuals with an underlying disease.