Johnson & Johnson (J&J) has reported initial data from the Phase II COV2008 clinical trial where a booster dose of its Ad26.COV2.S Covid-19 vaccine offered higher antibody and T-cell responses when given six months following the initial two-dose vaccine series with Pfizer-BioNTech’s BNT162b2.

The company noted that the latest results indicate the possible benefits of heterologous boosting or a mix-and-match of various vaccines.

Sponsored by J&J, the ongoing, blinded trial is assessing the company’s Covid-19 vaccine as a booster dose in adult subjects aged 18 years and above.

The booster dose is recommended by the Advisory Committee on Immunization Practices (ACIP) of the US Centers for Disease Control and Prevention (CDC ) for adults who have already received initial dosing with an authorised Covid-19 vaccine.

Findings showed that J&J’s booster vaccine, following a BNT162b2 two-dose series, provided an increase in CD8+ T-cell responses versus the BNT162b2 booster.

Furthermore, four weeks after the booster dose with both J&J and Pfizer-BioNtech’s vaccine, similar neutralising and binding antibody levels against the original strain, Delta and Beta variants of SARS-CoV-2 virus were reported.

However, on mixing and matching J&J’s booster shots, antibodies continued to rise for at least four weeks while antibodies waned from week two to week four in people who were given a homologous booster of BNT162b2.

Previously reported preliminary data from the COV-BOOST trial in the UK supports these Phase II results, which comprised a subset of subjects from the Janssen-sponsored COV2008 trial.

In the COV-BOOST trial, using J&J’s booster shot in individuals who received two doses of either Pfizer-BioNTech’s vaccine or AstraZeneca ’s ChAdOx1 nCov-19 raised both antibody and T-cell responses.

J&J Janssen Research & Development global head Mathai Mammen said: “These results provide valuable scientific insights for our vaccine when used as a mix-and-match booster and can help inform boosting strategies with the goal to curb the pandemic.

“These data add to the growing body of evidence demonstrating that a mix-and-match booster dose of the Johnson & Johnson Covid-19 vaccine successfully increases humoral responses and cellular responses against the original strain of SARS-CoV-2, as well as the Beta and Delta variants.”

In August, J&J reported interim results from two Phase I/IIa trials where its Covid-19 booster shot elicited a quick and strong rise in spike-binding antibodies.