Johnson & Johnson (J&J) has reported that its single-dose Covid-19 vaccine stimulated robust, continued neutralising antibody activity against the Delta (B.1.617.2) variant, as well as other SARS-CoV-2 viral variants.

The data is from an analysis of blood samples collected from a subset of subjects in the Phase III ENSEMBLE clinical trial.

The vaccine triggered a higher neutralising antibody activity against the Delta variant as compared to activity against the Beta (B.1.351) variant in South Africa, where increased efficacy against severe or critical Covid-19 was observed.

According to results from the ENSEMBLE trial, the vaccine had an efficiency of 85% against severe or critical disease and showed protection against hospitalisation and death.

Furthermore, the vaccine was found to be effective in all regions analysed worldwide, including in South Africa and Brazil, the regions where an increased incidence of Beta and Zeta (P.2) variants were seen during the study.

As per a sub-study of the J&J’s Phase I/IIa trial, the durability of humoral and cellular immune responses induced by the Covid-19 vaccine lasted for a minimum of eight months, the latest time point analysed so far.

In addition, T-cell responses, including CD8+ T-cells that detect and kill infected cells, continued during the evaluated duration of eight months.

Johnson & Johnson Janssen Research & Development (R&D) global head Mathai Mammen said: “Current data for the eight months studied so far show that the single-shot Johnson & Johnson Covid-19 vaccine generates a strong neutralising antibody response that does not wane. Rather, we observe an improvement over time.

“In addition, we observe a persistent and particularly robust, durable cellular immune response.”

The J&J vaccine is authorised for emergency use in the US for active immunisation to prevent Covid-19 in adults.

In a separate development, Moderna has reported that the production of drug products required for its Covid-19 vaccine has commenced at Recipharm’s Monts facility in France.

The facility received the European Medicines Agency’s (EMA) Committee for Human Medicines approval last month for the vaccine manufacturing.