A potential HIV vaccine being developed by Johnson & Johnson did not provide protection against the virus in a mid-stage study, the pharmaceutical company has said.
J&J plans to end the study, which involved young women in sub-Saharan Africa.
But researchers will continue a separate, late-stage trial involving a different composition of the vaccine in men and transgender people.
The study in sub-Saharan Africa involved about 2,600 women who were deemed to be at high risk of acquiring HIV, which causes Aids.
Participants were randomly selected to receive either the vaccine or a placebo, and researchers found that the vaccine was only 25% effective at preventing HIV.
“HIV is a unique and complex virus that has long posed unprecedented challenges for vaccine development because of its ability to attack, hijack and evade the human immune system,” J&J chief scientific officer Dr Paul Stoffels said in a statement.
J&J said its other study of the potential vaccine is being conducted in Europe and the Americas, where different strains of HIV are circulating.
Johnson & Johnson, based in New Brunswick, New Jersey, also makes one of the three vaccines approved by US regulators for the prevention of Covid-19.
J&J is also developing vaccines for sepsis and respiratory syncytial virus.