In January 2023 Janssen and global partners announced the results of an “independent, scheduled data review” of a Phase III Mosaico study of Janssen’s investigational HIV vaccine regimen. The Data and Safety Monitoring Board (DSMB) established that although there were no safety issues with the vaccine regimen, it was ineffective in preventing HIV infection compared to placebo. Consequently, the Mosaico clinical trial will be discontinued.  


The study began in 2019 and completed vaccinations in October 2022. It enrolled “approximately 3,900 cisgender and transgender people who have sex with cisgender men and/or transgender people”. This group represented populations “vulnerable to HIV”. The trial took place across 50 sites.  

The study evaluated an investigational vaccine regimen of a mosaic-based adenovirus serotype 26 vector (Ad26.Mos4.HIV). This was administered during 4 vaccination visits throughout one year. A mix of soluble proteins, adjuvanted with aluminium phosphate, was also administered during visits 3 and 4.  

A statement from the US NIH identified “funding support” from NIAID and “additional study support” from the US Army Medical Research and Development Command. 

DSMB analysis 

Using currently available data the analysis revealed that the regimen “does not protect against HIV and the study is not expected to meet its primary endpoint”. This comes after the primary analysis of the Phase IIb Imbokodo study, in which a similar investigational regimen did not provide adequate protection against HIV in young women.  

As a result of this determination, the trial is to be discontinued and participant notifications are underway.  

A disappointing outcome 

Dr Penny Heaton of Janssen is “disappointed with this outcome” but emphasised that the organisation stands “in solidarity” with those “vulnerable to and affected by HIV”. She acknowledged “significant advances in prevention” but referred to the 1.5 million people who acquired HIV in 2021 as evidence of the “unmet need for new options”.  

“We remain steadfast in our commitment to advancing innovation in HIV, and we hope the data from Mosaico will provide insights for future efforts to develop a safe and effective vaccine.”

For discussion on the future of HIV vaccines at the World Vaccine Congress in April, get your tickets today.