Figure 1.

Study flow diagram, inclusion and exclusion criteria, case–control study on COVID-19 booster vaccine effectiveness, United Kingdom, April 2022–January 2023 (n = 9,868)

The left panel describes the spring-summer monovalent booster analysis; of the 182 SARS-CoV-2-positive individuals, 78 were vaccinated with fourth-dose monovalent mRNA vaccine and 104 were vaccinated with third-dose monovalent mRNA vaccine. Of the 682 SARS-CoV-2-negative individuals admitted, 413 were vaccinated with fourth-dose monovalent mRNA vaccine and 269 were vaccinated with third-dose monovalent mRNA vaccine.

The right panel describes the autumn-winter bivalent booster analysis; of the 152 SARS-CoV-2-positive individuals, 100 were vaccinated with fifth-dose bivalent mRNA vaccine and 52 were vaccinated with fourth-dose monovalent mRNA vaccine. Of the 732 SARS-CoV-2-negative individuals admitted, 572 were vaccinated with fifth-dose bivalent mRNA vaccine and 160 were vaccinated with fourth dose monovalent mRNA vaccine.