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. These data are consistent with preclinical studies, published in the scientific journal Nature, which showed that a single dose of the vaccine successfully prevented subsequent infection and provided complete protection in the lungs of nonhuman 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.
The full set of results will be published once the complete Phase 1/2a trial data are available.
Immune Response Data
Seroconversion (the development of detectable antibodies) was observed in 99 percent of participants aged 18-55 years of age. 98 percent 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.
Safety and Tolerability Data
Interim safety data from the Phase 1/2a trial indicated that the majority of adverse events reported were mild to moderate (grade 1 and grade 2) in severity and generally occurred on the day of vaccination with symptoms generally resolving that day, or the following day. Two serious adverse events were reported, the first for hypotension which the investigator determined to not be vaccine related, and the second was a participant with a fever who was hospitalized due to suspicion of having COVID-19 but recovered within 12 hours. No grade 4 (life-threatening) adverse events, solicited or unsolicited, were reported in any cohort, and no participant discontinued the study due to an adverse event. The analysis showed there was a trend toward higher reactogenicity with the higher vaccine dose and with younger age.
In clinical studies investigating vaccines, it is well known that vaccines often induce local and systemic side-effects that are mild, to moderate, and transient without consequences. In vaccine clinical trials these type of side effects are actively sought ("solicited"). The interim safety data in this Phase 1/2a study is blinded to ensure participants and trial investigators are not made aware which participants received a single dose of Janssen’s COVID-19 vaccine candidate versus a placebo".