Johnson & Johnson (J&J) has started a Phase I/IIa clinical trial of its Covid-19 vaccine candidate, Ad26.COV2.S, in healthy volunteers across the US and Belgium.

The first-in-human trial comes after the vaccine candidate showed promise in preclinical studies, where the product was able to trigger a immune response against SARS-CoV-2.

This immune response involves the generation of neutralising antibodies that were able to prevent subsequent infection and provide complete or near-complete protection in the lungs of non-human primates (NHPs).

Beth Israel Deaconess Medical Center (BIDMC) researchers performed the pre-clinical studies in partnership with J&J unit Janssen Pharmaceutical and others.

According to the findings, out of seven vaccine prototypes assessed in the preclinical study, Ad26.COV2.S induced the highest levels of neutralising antibodies against SARS-CoV-2.

The company added that the six NHPs that received a single immunisation with its Covid-19 vaccine candidate had no detectable virus in the lower respiratory tract after exposure to the novel coronavirus.

Furthermore, only one of six NHPs had very low levels of the virus in a nasal swab at two time points.

The Phase I/IIa study will assess the safety, reactogenicity, and immunogenicity of Ad26.COV2.S in more than 1,000 healthy volunteers aged 18 to 55 years, and those aged 65 years and above.

Johnson & Johnson is also planning to conduct a Phase IIa study in the Netherlands, Spain and Germany, as well as a Phase I study in Japan.

The company’s Covid-19 clinical trial programme will also involve a Phase III study, which is expected to begin in September this year. The clinical programme is designed to assess one and two-dose regimens of the vaccine candidate in parallel studies.

Janssen Research & Development global head Mathai Mammen said: “Our pre-clinical results give us reason to be optimistic as we initiate our first-in-human clinical trial, and we are excited to enter the next stage in our research and development toward a Covid-19 vaccine.

“We know that, if successful, this vaccine can be rapidly developed, produced on a large scale and delivered around the world.”

J&J is working to boost its manufacturing capacity to potentially supply more than one billion doses of the Covid-19 vaccine candidate worldwide through 2021.