A new experimental HIV vaccine using the same approach as a leading COVID-19 vaccine candidate triggered production of neutralizing antibodies that protected monkeys, researchers reported at the International AIDS Conference in July. The most promising HIV vaccine candidates use harmless virus vectors to deliver HIV proteins. Moderna’s new vaccine instead administers messenger RNA (mRNA) that instructs cells to make virus-like particles. Over the course of a year, 16 monkeys received eight injections using various vaccine regimens and were rectally exposed to an HIV-like virus. They produced antibodies that bind to HIV envelope proteins, with the level and durability of these antibodies increasing after each booster shot. However, the response was not equally strong for all types of HIV. The vaccine offered “significant protection,” the researchers reported. Of the seven monkeys that received the most effective vaccine regimen, three did not become infected with the virus, and infection was delayed in the other four.