Johnson & Johnson Single-Dose COVID-19 Vaccine Demonstrates Lasting Immune Response in Early-Stage Trials

The COVID-19 vaccine candidate being developed by Janssen Pharmaceutical Companies of Johnson & Johnson leverages the company’s AdVac vaccine platform, which was also used to develop and manufacture Janssen’s European Commission-approved Ebola vaccine regimen and construct its Zika, RSV, and HIV investigational vaccine candidates. Janssen is investigating multiple doses and dosing regimens of its COVID-19 vaccine candidate to evaluate long-term efficacy. The company is studying a single-dose of its vaccine candidate in the Phase 3 ENSEMBLE trial, which completed enrollment on December 17, 2020, and a two-dose regimen in the Phase 3 ENSEMBLE 2 study which is ongoing at multiple clinical sites in Belgium and the US.

In the multi-center, randomized, double-blind, placebo-controlled trial that aims to evaluate the safety, reactogenicity, and immunogenicity of JNJ-78436735 at two dose levels, Janssen’s COVID-19 vaccine candidate provided an immune response that lasted for at least 71 days, the duration of time measured in this study in participants aged 18-55 years. Data demonstrated that, after a single vaccination, neutralizing antibodies against COVID-19 were detected in over 90% of study participants at Day 29 and 100% of participants aged 18-55 years at Day 57. These neutralizing antibodies remained stable through Day 71, currently the latest timepoint available in this ongoing study, in all participants aged 18-55 years. Thus, the interim analysis showed the safety profile and immunogenicity after a single dose of the COVID-19 vaccine candidate were supportive of further development.

The study also evaluated a two-dose regimen, in which the data showed that a second dose of the vaccine candidate, administered 56 days apart, was less reactogenic while it triggered more than a two-fold increase in antibodies against COVID-19. The full set of results for this Phase 1/2a study will be published once the complete trial data are available. Data on durability of immune responses in trial participants aged over 65 years will be available in late January and longer-term follow-up to one year is planned.

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