A leading health official at the XVII International AIDS Conference in Mexico City says that an AIDS vaccine has been elusive but there’s no reason to give up hope, The Globe and Mail reports.

“Our objective should be to stop this virus, and the best way to do so is with a vaccine,” says Tadataka Yamada, executive director of the global health program at the Bill & Melinda Gates Foundation. “We have to be unafraid to fail. The challenges are huge, but I have no doubt that we will live in a world without HIV some day.”

Many biological and social challenges persist in efforts to establish an AIDS vaccine, but Seth Berkley, president and CEO of the International AIDS Vaccine Initiative, says a “vaccine is possible” and it will come.