A new clinical study by Beth Israel Deaconess Medical Center (BIDMC) has revealed strong immune responses with Johnson & Johnson’s single-dose Covid-19 vaccine, Ad26.COV2.S.

The viral vector vaccine, which was developed in alliance with BIDMC, already obtained emergency use authorisation in the US based on its clinical efficacy data in symptomatic Covid-19 in the US, South Africa, and Latin America.

In the new study, BIDMC’s Center for Virology and Vaccine Research found antibody and cellular immune responses against the SARS-CoV-2 variants of concern, as well as the original strain.

Data showed immune responses generated by Ad26.COV2.S against all variants of the Covid-19 virus, researchers noted.

Study senior author and BIDMC immunologist Dan Barouch said: “The concern is whether SARS-CoV-2 variants may reduce the efficacy of current vaccines that were designed to protect against the original SARS-CoV-2 strain at the beginning of the pandemic.

“These findings therefore have important implications for vaccine protection against SARS-CoV-2 variants of concern.”

In the study, 20 participants aged 18 to 55 years received one or two doses of J&J’s vaccine to assess its immunogenicity.

These subjects were from a multi-centre, randomised, double-blind, placebo-controlled Phase I/IIa trial analysing different doses and schedules of the vaccine.

The BIDMC researchers subsequently leveraged various approaches to evaluate antibody and cellular immune responses against the original viral strain (WA1/2020).

They also tested for the viral variants first detected in South Africa (B.1.1351), the UK (B.1.1.7), Brazil (P.1), and California, US (CAL.20C).

A decrease in neutralising antibodies against the South African and Brazilian strains was observed compared to antibodies against the original strain.

However, SARS-CoV-2 variants had less or no impact on non-neutralising antibody responses and T cell responses.

As per the vaccine’s protective efficacy found in Phase III trials, non-neutralising antibodies and/or T cell responses may drive protection against Covid-19.

Published Phase III efficacy results revealed the vaccine’s strong protection against symptomatic Covid-19 in South Africa and Brazil where a majority of sequenced cases were due to variants.

According to researchers, the data helps in understanding the vaccine’s protection against SARS-CoV-2 variants of concern.