Experimental HIV vaccine safe but ineffective


An investigational HIV vaccine regimen was safe but did not provide protection against HIV, an independent data and safety monitoring board (DSMB) has determined. 

The regimen was tested among men who have sex with men (MSM) and transgender people. The HPX3002/HVTN 706, or ‘Mosaico’, Phase III clinical trial began in 2019 and involved 3,900 volunteers ages 18 to 60 years in Europe, North America and South America.  

Based on the DSMB’s recommendation, the study will be discontinued. Participants are being notified of the findings, and further analyses of the study data are planned. 

Janssen Vaccines & Prevention sponsored the Mosaico study with funding support from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. 

The experimental vaccine regimen was based on ‘mosaic’ immunogens – vaccine components featuring elements of multiple HIV subtypes – with the goal of inducing immune responses against a wide variety of global HIV strains.  

This vaccine candidate uses a common-cold virus (adenovirus serotype 26, or Ad26) to deliver the mosaic immunogens. The final two vaccinations were accompanied by a bivalent (two-component) HIV envelope protein formulation, combining clade C gp140 and mosaic gp140 envelope proteins, adjuvanted by aluminum phosphate to boost immune responses. 

No safety issues

In its scheduled data review, the DSMB determined there were no safety issues with the experimental vaccine regimen. However, the number of HIV infections were equivalent between the vaccine and placebo arms of the study.  

During the clinical trial, all participants were offered comprehensive HIV prevention tools, including pre-exposure prophylaxis, or PrEP.  Study staff ensured that participants who acquired HIV during the trial were promptly referred for medical care and treatment. 

In 2021, a DSMB also closed the Phase IIb ‘Imbokodo’ (HPX2008/HVTN 705) clinical trial, which was testing a similar HIV vaccine regimen in young women in sub-Saharan Africa, due to the vaccine being ineffective. 

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