Janssen vaccine effective against delta variant of COVID-19

The COVID-19 Delta variant is spreading around the world and preliminary data suggests the Janssen vaccine may protect against this variant.

With a number of COVID-19 vaccines in clinical testing, the Janssen vaccine, Ad26.COV2. S, has received emergency use authorization in more than 50 countries. The vaccine is designed to be given as a main dose without the need for a booster and studies have shown the vaccine to be 66.9% effective 14 days after administration. Nonetheless, while all available vaccines appear to be effective, with the emergence of an increasing number of variants, it is important to assess efficacy against these evolutionary mutants, particularly those, like the Delta variant, which appear to have a higher degree of transmissibility. While data from a small number of patients vaccinated with Ad26.COV2. S indicated a reduction in the binding titer of antibodies against certain variants, notably B.1.351 (South Africa), variant alpha (B.1.1.7, UK), functional non-neutralizing antibodies and responses of T cells were largely preserved after vaccination although the significance of these results is uncertain. As there is currently no data indicating whether Ad26.COV2. S is effective against the Delta COVID-19 variant, a team from Janssen Vaccines & Prevention, Leiden, The Netherlands, examined the binding and neutralization titers in vitro detected in sera from adults in the phase 3 trial EMSEMBLE against several worrisome variants, including the delta variant. Participants in the EMSEMBLE trial were immunized with a single dose of 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).

Results
Sera from a total of 8 patients, aged 47 to 91 years, were assessed for their ability to bind to B.1. Advanced protein and neutralization ability against COVID-19 variants using pseudo-virus neutralization assay. Neutralization against B.1.1.7 and B.1 was similar but for the other variants the binding was reduced. For example, it was reduced by 1.5 times against B.1.617, but the largest reductions occurred against B.1.351 (3.6 times) and B.1.617 (3.4 times). However, for the delta variant (B. 1.167.2), there was only a 1.6-fold reduction in neutralizing sensitivity.

In their discussion, the authors noted that in the absence of actual data, the efficacy of Ad26.COV2. S against the delta variant remains unknown, but confirmation of its efficacy could result from ongoing phase III trials. Nonetheless, using UK data showing how the two Pfizer-BioNTech vaccines appear to be effective against the Delta variant, the authors suggest that it is likely that this is also true for Ad26.COV2. S. They concluded that although the titers of neutralizing antibodies in vitro against the delta variant were found to be lower, the levels are still sufficient to protect individuals and that the increased response to non-neutralizing antibodies may also prove to be a relevant factor.

Quote
Jongeneelen M et al. Ad26.COV2. Neutralizing activity achieved against Delta and other variants of SARSCoV2.S of concern. BioRxiv 2021 pre-release