ABSTRACT
OBJECTIVE: Emerging evidence indicates that longer SARS-CoV-2 vaccine dosing intervals results in an enhanced immune response. However, the optimal vaccine dosing interval for achieving maximum immunogenicity is unclear. METHODS: This study included samples from adult paramedics in Canada who received two doses of either BNT162b2 or mRNA-1273 vaccines and provided blood samples six months (170 to 190 days) after the first vaccine dose. The main exposure variable was vaccine dosing interval (days), categorized as "short" (first quartile), "moderate" (second quartile), "long" (third quartile), and "longest" interval (fourth quartile). The primary outcome was total spike antibody concentrations, measured using the Elecsys SARS-CoV-2 total antibody assay. Secondary outcomes included spike and receptor-binding domain (RBD) immunoglobulin G (IgG) antibody concentrations, and inhibition of angiotensin-converting enzyme 2 (ACE-2) binding to wild-type spike protein and several different Delta variant spike proteins. We fit a multiple log-linear regression model to investigate the association between vaccine dosing intervals and the antibody concentrations. RESULTS: A total of 564 adult paramedics (mean age 40 years, SD=10) were included. Compared to "short interval" (≤30 days), vaccine dosing intervals of the long (39-73 days) group (ß= 0.31, 95% Confidence interval (CI): 0.10-0.52) and the longest (≥74 days) group (ß = 0.82. 95% CI: 0.36-1.28) were associated with increased spike total antibody concentration. Compared to the short interval, the longest interval quartile was associated with higher spike IgG antibodies, while the long and longest intervals were associated with higher RBD IgG antibody concentrations. Similarly, the longest dosing intervals increased inhibition of ACE-2 binding to viral spike protein. CONCLUSION: Increased mRNA vaccine dosing intervals longer than 38 days result in higher levels of anti-spike antibodies and ACE-2 inhibition when assessed six months after the first COVID-19 vaccine.
ABSTRACT
The gold standard of molecular pathogen detection is the quantitative polymerase chain reaction (qPCR). Modern qPCR instruments are capable of detecting 4-6 analytes in a single sample: one per optical detection channel. However, many clinical applications require multiplexing beyond this traditional single-well capacity, including the task of simultaneously testing for SARS-CoV-2 and other respiratory pathogens. This can be addressed by dividing a sample across multiple wells, or using technologies such as genomic sequencing and spatial arrays, but at the expense of significantly higher cost and lower throughput compared with single-well qPCR. These trade-offs represent unacceptable compromises in high-throughput screening scenarios such as SARS-CoV-2 testing. We demonstrate a novel method of detecting up to 20 targets per well with standard qPCR instrumentation: high-definition PCR (HDPCR). HDPCR combines TaqMan chemistry and familiar workflows with robust encoding to enable far higher levels of multiplexing on a traditional qPCR system without an increase in cost or reduction in throughput. We utilize HDPCR with a custom 20-Plex assay, an 8-Plex assay using unmodified predesigned single-plex assays from Integrated DNA Technologies and a 9-Plex pathogen panel inclusive of SARS-CoV-2 and other common respiratory viruses. All three assays were successful when tested on a variety of samples, with overall sample accuracies of 98.8, 98.3, and 100%, respectively. The HDPCR technology enables the large install base of qPCR instrumentation to perform mid-density multiplex diagnostics without modification to instrumentation or workflow, meeting the urgent need for increased diagnostic yield at an affordable price without sacrificing assay performance.