Johnson & Johnson COVID-19 Vaccine Generates Strong Immune Response in Mid-Stage Trials

Interim analysis from the ongoing Phase 1/2a clinical trial of the COVID-19 vaccine candidate (JNJ-78436735) from Johnson & Johnson’s (New Brunswick, NJ, USA) Janssen Pharmaceutical Companies (Beerse, Belgium) supports its further clinical development.

The data demonstrate that a single dose of JNJ-78436735 induced a strong neutralizing antibody response in nearly all participants aged 18 years and older and was generally well-tolerated. Immune responses were similar across the age groups studied, including older adults. The ongoing Phase 1/2a clinical trial is designed to study the safety and immunogenicity of two dose levels of the Janssen COVID-19 vaccine, and as single and two-dose schedules. The interim analysis showed that a single dose induced a robust immune response and was generally well-tolerated.


Seroconversion (the development of detectable antibodies) was observed in 99% of participants aged 18-55 years of age. 98% of participants were positive for neutralizing antibodies against SARS-CoV-2 at day 29 post-vaccination. The Janssen COVID-19 vaccine candidate elicited strong antibody responses, strong T cell responses, and a Th1 response, believed to be protective against the risk of vaccine-associated enhanced respiratory disease. Immunogenicity (the ability to trigger an immune response) data from participants aged 65 years of age and above were available for the first 15 participants at the time of this post, with strong humoral and cellular immune responses elicited in all elderly participants who received a single dose of Janssen’s COVID-19 vaccine candidate. Immune responses were similar across the age groups studied, including older adults.

These data are consistent with preclinical studies which showed that a single dose of the vaccine successfully prevented subsequent infection and provided complete protection in the lungs of non-human primates. Based on these findings, the single dose of the Janssen COVID-19 vaccine candidate of 5x1010 virus particles (vp) has been selected for further evaluation in the Phase 3 ENSEMBLE clinical trial. The company also plans on running a Phase 3 clinical trial of a two-dose regimen of JNJ-78436735 versus placebo later this year.

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