High-Throughput Assay Tracks Range of SARS-CoV-2 Vaccination Responses

The Elecsys Anti-SARS-CoV-2 S (ACOV2S) assay is highly valuable for tracking immune responses to SARS-CoV-2 vaccination, according to a study published in Infectious Diseases and Therapy.

“There is a need for automated, high-throughput assays to quantify immune response after SARS-CoV-2 vaccination,” researchers explained in the study introduction. “This study assessed the combined utility of the ACOV2S and the Elecsys Anti-SARS-CoV-2 (ACOV2N) assays using samples from the mRNA-1273 (Spikevax) phase 2 trial (NCT04405076).”

Researchers compared ACOV2S and live virus microneutralization assay results for participants in different subgroups at days 1 (first vaccination), 15, 29 (second vaccination), 43, and 57. The study included 593 healthy adults in two age groups: 18 through 54 years, and 55 years and older. Participants received two injections with either placebo, 50 μg of mRNA-1273, or 100 μg of mRNA-1273.

For the vast majority of participants, ACOV2S readily detected receptor-binding domain-specific antibodies at the first assessment after vaccination, according to the study. The assay showed that nonconverters were predominantly older, and at day 29, before the second dose, all participants demonstrated seroconversion.

On day 15, geometric mean concentration of antibody levels was 1.37-fold higher in the 100-μg group compared with the 50-μg group, the assay indicated. The difference decreased to 1.09-fold by day 43, which was 2 weeks after the second dose. In both groups, the response on day 15 and day 29 was more pronounced in younger participants. 

In the eight participants with previous SARS-CoV-2 infection identified with the ACOV2N assay, ACOV2S results for humoral response after vaccination were notably high compared with participants without previous SARS-CoV-2 infection, the study found.

“Our results show that the ACOV2S assay can track vaccine-related immune responses with a wide dynamic range and with good agreement with a live virus microneutralization assay,” researchers advised. “Combining the ACOV2S and ACOV2N assays enables breakthrough infections to be detected or for the impact of previous native infections on vaccine response to be evaluated.”

Reference:
Kirste I, Hortsch S, Grunert VP, et al. Quantifying the vaccine-induced humoral immune response to spike-receptor binding domain as a surrogate for neutralization testing following mRNA-1273 (Spikevax) vaccination against COVID-19. Infect Dis Ther. 2023;12(1):177-191. doi:10.1007/s40121-022-00711-y