Hani Kaba (Göttingen / DE), Nikita Srivastava (Göttingen / DE), Felix Hartkopf (Berlin / DE), Josué Alan Bucio Garcia (Göttingen / DE), Michael Kleines (Aachen / DE), Franz-Christoph Bange (Hannover / DE), Tim Eckmanns (Berlin / DE), Simone Scheithauer (Göttingen / DE)
Introduction
The emergence of omicron SARS-CoV-2 resulted in the displacement of delta and later displacement events between omicron variants. However, patterns of dominance intervals varied geographically within and between countries.
Goals
Starting from the hypothesis that any single vaccination influences pandemic developments, we investigated whether vaccination densities influenced dominance intervals of the most prevalent variants in 16 German federal states (BL).
Materials & Methods
Our weekly data (01/2021–01/2023) consisted of >1.1M SARS-CoV-2 sequences from DESH, IMS-SC2 and GISAID. Duplicates were removed as were sequences with a N content of ≥95% and weeks with n<10 reported sequences. Displacement occurred when a given cluster made ≥50% of all sequences (tp). We calculated the time-to-displacement interval (TTD) for omicron (1.1.529* variants) displacing delta (1.617.2*), BA.2 (1.1.529.2*) displacing BA.1 (1.1.529.1*) and BA.5 (1.1.529.5*) displacing BA.2. TTD was the interval [weeks] between the onset (first report) and tp. The displaced variant cluster was dubbed "predecessor", and the new dominant cluster "successor". We used Cox Regression to model TTD in 48 independent displacement events (3x16 BL), controlling for selected covariates (Fig. 1).
Results
Our model proposed a 12% [4; 21%] CI-95% increased risk of displacement for every outdated vaccine administration per 100 population. In contrast, every original vaccine administration per 100 population led to a 9% [3; 14%] decreased displacement risk (Fig. 1). The effect of low outdated vaccine density was most apparent in the delta-omicron event (mean ∆TTD 2.5 weeks [-0.6; 5.6] 95%-CI, log-rank test p=0.05), in contrast to BA.1-BA.2 (0.3, p=0.75) and BA.2-BA.5 (0.8, p=0.35).
Summary
Vaccine densities at BL-level influenced TTD in two ways. Vaccines administered before omicron onset helped delaying the displacement of delta. When the same vaccines became outdated due to omicron onset (immune evasive), they helped to accelerate delta displacement by omicron. The effect size dropped in following intra-omicron displacement events. Further research is needed to investigate causality.