Table 1 Comparison of endpoints of vaccine trials. The mode of action of the vaccine will determine the type of trial and endpoint that is used to evaluate their efficacy.

Pre-erythrocytic

Sporozoite challenge (Phase IIa)

Infection

$1-\frac{N_V}{N_{UV}}$

Daily ACD

[30, 31]

Delayed patency (if vaccinees become infected)

--

Daily ACD

[32–34]

Number of primary merozoites**

$1-\frac{{\stackrel{⌢}{P}}_V}{{\stackrel{⌢}{P}}_{UV}}$

Daily ACD

[5]

Field trial in endemic setting (Phase IIb/III)

Time to first infection or first episode

1-HR

ACD (for time to infection) ACD or PCD (for first episodes)

[35, 36]

Incidence of disease episodes

$1-\frac{I_V}{I_{UV}}$

ACD or PCD

For multiple episodes [36]

Blood stage

Field trial in endemic setting

Incidence of disease episodes (first episode or multiple episodes) (Phase IIb/III)

$1-\frac{I_V}{I_{UV}}$

ACD or PCD

[15, 16, 37]

Density of infection (Phase IIb)

$1-\frac{{\stackrel{⌢}{D}}_V}{{\stackrel{⌢}{D}}_{UV}}$

ACD

[9]