While evidence shows that COVID-19 vaccines are effective against the first SARS-CoV-2 variant that that was the dominant strain at the time that they were produced, as the vaccine rollout continues, whether the current vaccines will protect against the variants that have emerged more recently has remained an open question.

Now, Dan Barouch, M.D., Ph.D., director of Beth Israel Deaconess Medical Center’s (BIDMC) Center for Virology and Vaccine Research—who helped develop Johnson & Johnson’s COVID-19 vaccine (Ad26.COV2.S)—reported on the antibody and cellular immune responses generated by the vaccine against the original viral strain and against SARS-CoV-2 variants of concern. The team found that the J&J vaccine induced immune responses against all the viral variants.

This work is published in Nature, in the paper, “Immunogenicity of Ad26.COV2.S vaccine against SARS-CoV-2 variants in humans.”

In the three months since J&J’s COVID-19 vaccine received emergency use authorization from the FDA, more than 10 million Americans have received the vaccine, according to the Centers for Disease Control and Prevention.

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

To explore the immunogenicity of the vaccine, Barouch and colleagues administered one or two doses of J&J’s investigational vaccine to 20 volunteers between the ages of 18 and 55. All volunteers were participants of a larger multicenter, randomized, double-blind, placebo-controlled Phase I/IIa study to evaluate the vaccine at various doses and schedules.

The researchers then used multiple methods to assess antibody and cellular immune responses against the original viral strain (WA1/2020) and against the viral variants first identified in South Africa (B.1.1351 or beta), the United Kingdom (B.1.1.7 or alpha), Brazil (P.1 or gamma), and California (CAL.20C or epsilon).

Compared to antibody responses against WA1/2020, the data showed reductions in neutralizing antibodies against the B.1.1351 and P.1 strains. In contrast, non-neutralizing antibody responses and T-cell responses were minimally impacted or not impacted by SARS-CoV-2 variants. Given the vaccine’s protective efficacy as demonstrated in Phase III clinical trials, non-neutralizing antibodies and/or T-cell responses may contribute to protection against COVID-19.

The published Phase III efficacy data showed that the Ad26.COV2.S vaccine offered strong protection against symptomatic COVID-19 in South Africa and Brazil where most sequenced COVID-19 cases were caused by variants. The findings contribute to our understanding of vaccine protection against SARS-CoV-2 variants of concern.

“Although the mechanistic correlates of protection for COVID-19 are not yet known, the vaccine’s robust protective efficacy in these regions raises the possibility that non-neutralizing antibodies and/or T-cell responses may also contribute to protection,” said Barouch. “Alternatively, it is possible that low levels of neutralizing antibodies are sufficient for protection against COVID-19.”