1/6 Our paper today – www.nature.com/articles/s41... work from Kenya - shows protective antibodies against falciparum malaria sporozoites work against sporozoites injected into the skin, not against sporozoites injected into veins. Why does this matter?

3/6 Mosquitoes inject malaria sporozoites mostly into the skin, sometimes into blood vessels. In animal models sporozoites are more easily blocked in the skin compared with in blood vessels. Is this true in humans? We injected sporozoites into vaccinated volunteers.

4/6 All unvaccinated volunteers got malaria. None of the R21 vaccinated volunteers getting skin sporozoites got infected. All the R21 vaccinated volunteers getting intravenous sporozoites got infected.

5/6 This means if we want a hard and fast antibody level to predict protection, we need to look for different levels for skin sporozoites versus intravenous sporozoites.