Janssen presents one-shot COVID-19 vaccine data

Janssen Pharmaceuticals’ Phase III adenoviral vector vaccine JNJ-78436735 gave immune protection over two and a half months after a single vaccine shot of 5 x 10¹⁰ virus particles, according to a medRxiv preprint, now updated in the New England Journal of Medicine. This means that the vaccine, that is expected to be ready for EMA assessment in April 2021 might be given as single dose vaccination that could be boosted when enough vaccine has been produced some months later.

A second vaccination, indeed, increased neutralizing antibody titers nearly threefold albeit antibodies directed against the adenoviral vector 26 were present in the blood of people who got the first shot. However, a single shot was suffficient to induce neutralizing antibody titers in 96% and T cell responses in  at least 80% of the vaccinated volunteers.

Competing adenoviral vaccine candidates hat shown substantially lower antibody and T cell responses due to presence of anti-adenoviral antibodies in the blood of volunteers. According to Janssen Pharmaceuticals J&J’s adenovirus 26 vector showed little preexisting antivector immunity in clinical trials. According to J&J it is not yet known if the observed immunity is a sterilising immunity or just ameliorates
viral titers while leaving vaccinated people infectious.

Politicians across the world are convinced that a vaccine-induced herd immunity of 70% would be sufficinet to end the pandemic. However, herd immunity would only be achieved with vaccines that mediate sterilising immunity and depends on multiple still unknown factors such as durability of immune protection if any.

In a second Phase II trial, J&J is testing a two-dose administration scheme, separated by eight weeks.