IAS 2019 — Advances in HIV-1 prophylactic vaccines

  • Laura Vargas-Parada, Ph.D.
  • Conference Reports
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  • Prophylactic vaccines are being developed as prevention tools for HIV infection. 
  • A pair of studies (APPROACH and ASCENT) presented advances at the International Aids Society conference.

Why this matters 

  • Both vaccines are built on previous research using mosaic immunogens that induce broad immune responses that protect against diverse HIV-1 strains.
  • Results suggest that a 4-immunization vaccine regimen may produce long-term immune responses that are improved with the addition of mosaic gp140.
  • Follow-up new trial for expanded clade coverage MOSAIC will start in 2019. 

Study design 

  • APPROACH: Phase 1/2a, randomized, 2-year postvaccination follow-up of 2 vaccine regimens combining Ad26.Mos.HIV and clade C gp140 envelope protein to evaluate long-term (144 weeks) safety and immunogenicity in 65 healthy uninfected adults (ages 18-49 years).
  • ASCENT: Phase 2a, randomized, double-blind, placebo-controlled study evaluating safety and immunogenicity of 2 vaccine regimens comprising Ad26.Mos4.HIV and either clade C gp140 or bivalent gp140 plus adjuvant in 152 healthy adults (ages 18-50 years; 59% females).

Key results

    • Enduring humoral immune responses over 2 years. 
    • 100% response rate in the participants receiving the Ad26.Mos.HIV, gp140HD vaccine regimen. 
    • No safety issues observed. 
  • ASCENT:       
    • Both regimens were well-tolerated.
    • Immunogenicity-inducing binding and functional antibodies to all antigens tested were detected. 
    • At week 28, similar PTE Env ELISpot responses were observed, with medians of 444 and 452 SFU/10peripheral blood mononuclear cells in bivalent or clade C groups, respectively. 


  • APPROACH study was unblinded, follow-up continues; data presented without peer review at a conference.

Expert comment 

  • “These are very promising times in HIV vaccine research, with multiple efficacy clinical trials ongoing, new approaches in development, and a growing sense that we may be getting closer to an effective vaccine,” Roger Tatoud, director of the Global HIV Vaccine Enterprise, said in a statement.