Recently, BA.5, one of the most contagious Omicron subvariants of the coronavirus disease 2019 (COVID-19), has been spreading rapidly. In addition, as South Korea confirmed its first case of BA.2.75, a new highly-mutated subvariant of the virus – nicknamed “Centaurus” – concerns have grown even further. Since early July, the number of new COVID-19 cases in Korea has doubled every week for nearly three weeks, reaching 100,000 cases on July 26th. Hence, the government has recommended a fourth round of COVID-19 vaccinations for those in high-risk groups. These include people over 50, as well as those over 18 with underlying health conditions. There is a need for caution regarding when the fourth shot should be taken. For those who have not been infected, receiving the shot four months after the third dose is recommended. Those that have experienced a breakthrough infection may receive it three months after their last dose. However, if one is infected within 30 days of receiving the third dose, they should wait an additional month before receiving the next dose. Meanwhile, public opinions have questioned why a fourth vaccine dose is being provided with past vaccines, rather than “enhanced” vaccines. Nevertheless, the effectiveness of the enhanced vaccines is still uncertain. Thus, it is crucial to quickly provide the existing vaccines to the high-risk group to prevent serious illness, hospitalization, and death.