Few vaccines have been as complicated—and filled with false starts and crushed hopes—as the development of an HIV vaccine

While antivirals help HIV-positive patients live longer and reduce viral transmission to virtually nil, these medications must be taken for life, and preventative medications like pre-exposure prophylaxis, known as PrEP, need to be taken every day to be effective. Vaccines, even if they need boosters, would make prevention much easier. Read more at Leaps.