A large clinical trial in South Africa and Uganda has shown that a twice-yearly injection of a new drug, provides young women with total protection against HIV infection. The trial tested whether the six-month injection of lenacapavir would provide better protection against HIV infection than two other pills, which need to be taken daily. All three medications are pre-exposure prophylaxis drugs. We speak to globally renowned HIV scientist and epidemiologist - Professor Salim Abdool Karim