J&J starts clinical study of COVID-19 vaccine, including one-dose regimen

Johnson & Johnson announced Thursday that a Phase I/IIa study of its COVID-19 vaccine candidate Ad26.COV2.S in healthy volunteers has started in the US and Belgium following positive preclinical data. The trial, as well as a potential Phase III study, will evaluate both one- and two-dose regimens of the adenovirus serotype 26 (Ad26) vector-based vaccine in parallel studies.

"We are excited to see these preclinical data because they show our SARS-CoV-2 vaccine candidate generated a strong antibody response and provided protection with a single dose," remarked Paul Stoffels, Johnson & Johnson's chief scientific officer. Stoffels added "the findings give us confidence as we progress our vaccine development and upscale manufacturing in parallel, having initiated a Phase I/IIa trial in July with the intention to move into a Phase III trial in September."

Studies in more countries planned

Johnson & Johnson noted that the Phase I/IIa trial will evaluate Ad26.COV2.S in over 1000 adults aged 18 to 55 years, as well as adults aged 65 years and older. The company added that planning is also under way for a Phase IIa study in the Netherlands, Spain and Germany, as well as for a Phase I study in Japan.

Meanwhile, Johnson & Johnson indicated that discussions are ongoing regarding initiating a pivotal Phase III trial of the single vaccine dose versus placebo in September, pending interim data from Phase I and II. Simultaneously, the drugmaker also plans to start a parallel Phase III study of a two-dose regimen versus placebo.

Vaccine elicits "robust immune response"

Results published on Thursday in the journal Nature showed that Ad26.COV2.S protected against infection with SARS-CoV-2 in non-human primates, with the vaccine eliciting a "robust immune response" as demonstrated by neutralising antibodies, successfully preventing subsequent infection and providing complete or near-complete protection in the lungs. The study found that all six non-human primates that received a single immunisation with Ad26.COV2.S showed no detectable virus in the lower respiratory tract after exposure to SARS-CoV-2, and only one had very low levels of the virus in a nasal swab at two time points.

Data also indicated that the level of antibodies correlated with the level of protection, with Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, which conducted the preclinical work, noting that "antibody levels may serve as a biomarker for vaccine-mediated protection."

For related analysis, see ViewPoints: The COVID-19 vaccine race gets competitive – but should it?

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