Janssen COVID-19 Vaccine Elicits Immune Response for At Least 8 Months

In a recent correspondence, investigators from Harvard’s Center for Virology and Vaccine Research discuss interim immunogenicity and efficacy data which demonstrates that the Janssen COVID-19 vaccine, Ad26.COV2.S, elicited durable humoral and cellular immune responses with minimal decreases for at least 8 months after administration.

The data from the correspondence was published in The New England Journal of Medicine.

For the study, 20 participants received either 1 or 2 doses of the therapy (either 5×1010 viral particles or 1011 viral particles) and 5 participants received a placebo.

The investigators then evaluated both antibody and T-cell responses on day 239, which was 8 months after the 1 dose regimen in 10 participants and 6 months after the 2 dose regimen in 10 participants.

Findings demonstrated that all of the participants showed an antibody response on day 239. The median binding antibody titer against the WA1/2020 receptor-binding domain was 645 on day 29, 1772 on day 57, 1962 on day 71, and 1306 on day 239.

Regarding median WA1/2020 pseudovirus neutralizing antibody titers, they were 272 on day 29, 169 on day 57, 340 on day 71, and 192 on day 239. In participants who received only a single dose, titers were observed to be similar.

Over the 8-month period, antibody responses remained relatively stable. However, a reduction in median neutralizing antibody titers was observed by a factor of 1.8 between peak response on day 71 and the time point for assessing durability on day 239.

Those receiving the single dose regimen showed an expansion of neutralizing antibody breadth associated with improved coverage of SARS-CoV-2 variants over time, including increased neutralizing antibody titers against variants of concern.

“These data show that the Ad26.COV2.S vaccine elicited durable humoral and cellular immune responses with minimal decreases for at least 8 months after immunization,” the authors wrote. “The durability of humoral and cellular immune responses 8 months after Ad26.COV2.S vaccination with increased neutralizing antibody responses to SARS-CoV-2 variants over time, including after single-shot vaccination, further supports the use of the Ad26.COV2.S vaccine to combat the global Covid-19 pandemic.”