 Our study found that the COVID-19 mRNA vaccines are highly effective against symptomatic COVID-19, even with one dose. This suggests that the vaccine can provide protection against COVID-19 infection. Further research is needed to evaluate the vaccine effectiveness of other COVID-19 vaccines, COVID-19 breakthrough after vaccination, and vaccine efficacy against new variants. This article was authored by Alexandra Omora, Takaki Kobayashi, Hiroyuki Suzuki, and others.