For around 30 years we have lived under the spectre of HIV. In the early 1980s, the mysterious appearance of symptoms that would later be known as AIDS led to unprecedented efforts to unmask the cause. On 23 April 1984, Margaret Heckler, the US Secretary of Health and Human Services, told the world that scientists had identified the virus that was the probable cause of AIDS. She was correct. She also said that a vaccine would be “ready for testing in approximately two years.” She was wrong.

Despite 28 years of research, there is still no vaccine that provides effective protection against HIV, and in that time around 25 million people have died of HIV-related causes. To understand why creating