This Phase 1a study, conducted in malaria-naïve adults in Ireland, assessed the safety and immunogenicity of the chimpanzee adenovirus 63 and Plasmodium falciparum liver-stage antigen circumsporozoite protein (ChAd63 CS) vaccine candidate, with and without modified vaccinia Ankara (MVA CS). Volunteers were vaccinated with priming doses of 350 µL ChAd63 CS, with half of the volunteers receiving 350 µL ChAd63 CS diluted in 0.9% sodium chloride. A subset of volunteers in both groups received booster dosages of 350 µL MVA CS on day 56.
The study was designed with two objectives:
- Assess the safety of the ChAd63 CS vaccine given alone, and with MVA CS in a prime-boost regimen, in malaria-naïve adults by monitoring for occurrence of solicited and unsolicited serious adverse events during a 12-month follow-up period.
- Quantify the humoral and cellular immune responses generated by the ChAd63 CS vaccine given alone, and with MVA CS, via anti-CS antibody titer.
Outcomes/Next steps: Findings were published in PLoS ONE in 2014.
A variety of local and systemic reactions were noted in subjects; however, these were found to be in line with reactogenicity experienced in previous studies. All formulations induced high levels of antigen-specific multifunctional CD4+ and CD8+ T lymphocytes, and significant levels of antibody.
Based on the outcomes of this study, the PATH Malaria Vaccine Initiative went on to support a related efficacy study.
de Barra E, Hodgson SH, Ewer KJ, Bliss CM, Hennigan K, et al. A Phase Ia study to assess the safety and immunogenicity of new malaria vaccine candidates ChAd63 CS administered alone and with MVA CS. PLoS ONE. 2014;9(12):e115161.