We therefore investigated whether individuals (aged 4–15 years) from a malaria-endemic region of Tanzania had acquired antibodies that bind recombinant HB3var03 CIDRα1.4 and IT4var20 CIDRα1.1 domains and to what extent these antibodies can prevent EPCR binding by a diverse set of CIDRα1 domains. The gene discussed is PROCR; the disease is malaria.