Correct Answer : May 18th
Every year on May 18th, the world commemorates World AIDS Vaccine Day. The day is observed to honour the efforts of hundreds of scientists and medical professionals who are working persistently to develop a vaccine to combat the Human Immunodeficiency Virus (HIV).
The day is also known as HIV Vaccine Awareness Day, with the goal of raising awareness about the importance of HIV vaccinations in preventing HIV infection and AIDS.
WORLD AIDS VACCINE DAY HISTORY AND SIGNIFICANCE : World AIDS Vaccine Day honours healthcare workers, scientists, and volunteers who have dedicated their lives to the development of an effective and safe AIDS vaccine. After President Bill Clinton gave a speech at Morgan State University in 1997, stating that a vaccine was the only way to control the spread of HIV and eventually wipe it out, the day was commemorated for the first time in May 1998..
Source : India Today