CD4 and malaria: The present study undertook a subanalysis of data collected in the COSTOP (cotrimoxazole cessation) trial (ISRCTN44723643), a study designed to investigate the safety of stopping cotrimoxazole (CTX) in HIV-infected adults stable on ART, to assess whether malaria incidence differed between participants receiving different ART regimens and whether any such effects were modified by CTX use or CD4+ cell count.