Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK.
NIHR Oxford Biomedical Research Centre, Oxford, UK.
Clin Exp Immunol. 2023 Mar 24;211(3):280-287. doi: 10.1093/cei/uxad013.
The trajectory of immune responses following the primary dose series determines the decline in vaccine effectiveness over time. Here we report on maintenance of immune responses during the year following a two-dose schedule of ChAdOx1 nCoV-19/AZD1222, in the absence of infection, and also explore the decay of antibody after infection. Total spike-specific IgG antibody titres were lower with two low doses of ChAdOx1 nCoV-19 vaccines (two low doses) (P = 0.0006) than with 2 standard doses (the approved dose) or low dose followed by standard dose vaccines regimens. Longer intervals between first and second doses resulted in higher antibody titres (P < 0.0001); however, there was no evidence that the trajectory of antibody decay differed by interval or by vaccine dose, and the decay of IgG antibody titres followed a similar trajectory after a third dose of ChAdOx1 nCoV-19. Trends in post-infection samples were similar with an initial rapid decay in responses but good persistence of measurable responses thereafter. Extrapolation of antibody data, following two doses of ChAdOx1 nCov-19, demonstrates a slow rate of antibody decay with modelling, suggesting that antibody titres are well maintained for at least 2 years. These data suggest a persistent immune response after two doses of ChAdOx1 nCov-19 which will likely have a positive impact against serious disease and hospitalization.
在首次剂量系列之后，免疫反应的轨迹决定了疫苗效力随时间的下降。在这里，我们报告了在没有感染的情况下，按照两剂 ChAdOx1 nCoV-19/AZD1222 接种计划，在一年中免疫反应的维持情况，并且还探索了感染后抗体的衰减情况。与两剂标准剂量（批准剂量）或低剂量后接种标准剂量疫苗方案相比，两剂低剂量 ChAdOx1 nCoV-19 疫苗（两低剂量）的总刺突特异性 IgG 抗体滴度较低（P = 0.0006）。第一剂和第二剂之间的间隔时间越长，抗体滴度越高（P < 0.0001）；然而，没有证据表明抗体衰减的轨迹因间隔时间或疫苗剂量而有所不同，并且在接种第三剂 ChAdOx1 nCoV-19 后，IgG 抗体滴度的衰减遵循相似的轨迹。感染后样本的趋势相似，最初的反应迅速下降，但此后仍能保持可测量的反应。根据两剂 ChAdOx1 nCov-19 的抗体数据外推表明，抗体衰减速度较慢，建模表明，至少在 2 年内抗体滴度保持良好。这些数据表明，两剂 ChAdOx1 nCov-19 后会产生持久的免疫反应，这可能对严重疾病和住院治疗产生积极影响。
