In a 1988 essay on pandemics, Nobel laureate Joshua Lederberg wrote, “We have no guarantee that the natural evolutionary competition of viruses with the human species will always find ourselves the winner.”

The introduction of pre-exposure prophylaxis (PrEP) as a means of preventing HIV infections in those at high risk marked a significant step in the fight against the virus. PrEP involves taking the HIV medicine Truvada or a generic version daily. It is now gradually becoming available across the world...