The COVID-19 Delta variant is spreading around the world and preliminary data suggests the Janssen vaccine could protect against this variant.
With a number of COVID-19 vaccines in clinical testing, the Janssen vaccine, Ad26.COV2. S, has received emergency use authorisation in over 50 countries. The vaccine is designed to be given as a prime dose without the need for a boost and studies have shown a vaccine efficacy of 66.9%, 14 days after administration. Nevertheless, while all of the available vaccines appear to be effective, with the emergence of an increasing number variants, it is important to evaluate the efficacy against these evolving mutants, especially those, such as the Delta variant, which appear to have a greater degree of transmissibility. While data from a small number of patients vaccinated with Ad26.COV2. S have indicated a reduction in antibody binding titre against some variants including the B.1.351 (South Africa), the alpha variant (B.1.1.7, UK), functional non-neutralising antibody and T cell responses were largely preserved after vaccination although the significance of these findings are uncertain. As there are currently no data on whether the Ad26.COV2. S is effective against the Delta COVID-19 variant, a team from Janssen Vaccines & Prevention, Leiden, The Netherlands, have examined the in vitro binding and neutralising titres detected in sera of adults from the phase 3 EMSEMBLE trial against several variants of concern, including the delta variant. Participants in the EMSEMBLE trial were immunised with a single dose of the Ad26.COV2. S vaccine and sera collected 71 days and tested against a range of COVID-19 variants, including the original Wuhan strain and a number of variants, e.g., B.1, alpha (B.1.1.7), Beta (B.1.251), Zeta (P.2), Gamma (B.1.617) and Delta (B.1.617.2).
Sera from a total of 8 patients, ranging in age from 47 to 91 years, were assessed for the ability to bind to B.1. Spike protein and neutralising capacity against the COVID-19 variants using a pseudo-virus neutralisation assay. The neutralisation against B.1.1.7 and B.1 were similar but for the other variants, binding was reduced. For example, it was reduced 1.5-fold against B.1.617 but the greatest reductions occurred against B.1.351 (3.6-fold) and B.1.617 (3.4-fold). However, for the delta variant (B. 1.167.2), there was only a 1.6-fold reduction in neutralising sensitivity.
In their discussion, the authors noted that in the absence of real-world data, the efficacy of Ad26.COV2. S against the delta variant remains unknown but confirmation of its efficacy may arise from the ongoing Phase III trials. Nevertheless, using UK data showing how both the Pfizer-BioNTech vaccines appear to be effective against the Delta variant, the authors suggest it is likely that this will also be true for Ad26.COV2. S. They concluded that while in vitro neutralising antibody titres against the delta variant were found to be lower, levels are still sufficient to protect individuals and that the enhanced non-neutralising antibody response may also prove to be a relevant factor.
Jongeneelen M et al. Ad26.COV2. S elicited neutralising activity against Delta and other SARSCoV2.S variants of concern. 2021 BioRxiv preprint