J&J offers PhI/IIa data showing its single-dose vaccine can stir up sufficient immune response
Days after J&J dosed the first participants of its Phase III ENSEMBLE trial, the pharma giant has detailed the early-stage data that gave them confidence in a single-dose regimen.
Testing two dose levels either as a single dose or in a two-dose schedule spaced by 56 days in, the scientists from Janssen, the J&J subsidiary developing its vaccine, reported that the low dose induced a similar immune response as the high dose. The interim Phase I/IIa results were posted in a preprint on medRxiv.
A single dose of Ad26.COV2.S elicited strong humoral responses in the vast majority of vaccine recipients. S-binding antibody titers as measured by ELISA, increased from baseline to Day 29 post vaccination in 99% of the participants in cohort 1a and 100% of the first participants in cohort 3, independent of the vaccine dose level that was given.
When it comes to neutralizing antibodies, 98% had detectable neutralizing antibodies against the wild-type virus after 29 days.
The J&J scientists made note of the fact all other Covid-19 vaccines currently in development require two doses, but everyone who had a neutralizing antibody response on their candidate obtained it after a single dose.
A challenge study they’ve conducted in monkeys support this funding, they added: Previously disclosed preclinical data showed that a single dose provided complete protection against SARS-CoV-2 replication in the lung and near-complete protection against viral replication in the nose.”
Interestingly, the results suggested that older adults may be less likely to experience side effects on the vaccine.
“Although the safety data in this interim report remain blinded, the overall occurrence independent of dose level of solicited systemic AEs of 64% with a 19% fever rate (5% grade 3) in adults aged 18 to 55 (Cohort 1a and 1b) stands in contrast to the solicited systemic AEs of 36% with a 4% fever rate (0% grade 3), found in the participants ≥ 65 years of age,” the researchers wrote.
Leveraging a recombinant version of adenovirus serotype 26 (Ad26) that can’t replicate as the vector, J&J’s Ad26.COV2.S consists of a transgene cassette encoding a prefusion stabilized SARS-CoV-2 spike protein, derived from the first clinical isolate of the Wuhan strain.
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