Photo Credit: Jira Pliankharom
The following is a summary of “Real-time estimation of immunological responses against emerging SARS-CoV-2 variants in the UK: a mathematical modelling study,” published in the September 2024 issue of Infectious Disease by Russell et al.
The emergence of SARS-CoV-2 variants and COVID-19 vaccination causes complex exposure histories; quick assessment on neutralizing antibodies against SARS-CoV-2 infection was critical for vaccine strategies and epidemic management.
Researchers conducted a retrospective study to investigate the population heterogeneity at individual and population-level antibody kinetics to emerging SARS-CoV-2 variants based on earlier exposure history, study implications for real-time analysis, and evaluate the outcomes of vaccine-campaign timing.
They designed a Bayesian hierarchical model of antibody kinetics to estimate neutralizing antibody trajectories against SARS-CoV-2 variants by individual-level vaccination and infection histories. Antibody titer trajectories were modeled by piecewise linear functions with basic biological quantities: initial titer value, peak titer time, set-point time, and increase/decrease rates. Process parameters were set at individual and population levels. Data from participants in the University College London Hospitals–Francis Crick Institute Legacy study cohort (NCT04750356) were studied. Participants underwent SARS-CoV-2 surveillance via asymptomatic or symptom-based testing, were segmented to include vaccination events up to 150 days before delta, BA.2, and XBB 1.5 variants occurred and were split into real-time (up to the emergence date) and retrospective (until the next SARS-CoV-2 exposure) datasets.
The results showed that from 335 participants in the delta wave, 223 (67%) were female and 112 (33%) male, with a median age of 40 years (interquartile range 22–58). In the BA.2 wave analysis, 385 participants consisting of 271 (70%) females and 114 (30%) males, with a median age of 41 years (22–60), for the XBB 1.5 wave, 248 participants were reviewed, with 191 (77%) females and 56 (23%) males, with 1 participant (<1%) who did not disclose the gender, with a median age of 40 years (21–59). While the analysis had 968 vaccination exposures across 1,895 serum samples. Peak titer values for the delta wave were calculated at 490.0 IC50 (95% credible interval 224.3–1515.9) for individuals with no prior infection and 702.4 IC50 (300.8–2322.7) for those with previous infections before the omicron variant, for the BA.2 wave, peak titer values were calculated as 858.1 IC50 (689.8–1363.2) for participants without previous infection, 1,020.7 IC50 (725.9–1722.6) for those infected before omicron, and 1,422.0 IC50 (679.2–3027.3) for those infected previously with omicron. In the XBB 1.5 wave, estimated peak titers were 703.2 IC50 (415.0–3197.8) for individuals without prior infection, 1,215.9 IC50 (511.6–7338.7) for those with the previous infection before omicron, and 1,556.3 IC50 (757.2–7907.9) for those with last omicron infection.
They concluded the real-time estimation of antibody kinetics preexisting the emergence of SARS-CoV-2 variants was viable and important for interpreting exposure combinations and vaccination timing on population-level immunity.
Source: thelancet.com/journals/laninf/article/PIIS1473-3099(24)00484-5/fulltext
