Manaaki Whenua, Lincoln, New Zealand.
Mathematics and Statistics, University of Canterbury, Christchurch, New Zealand.
J R Soc Interface. 2023 Feb;20(199):20220698. doi: 10.1098/rsif.2022.0698. Epub 2023 Feb 1.
New Zealand experienced a wave of the Omicron variant of SARS-CoV-2 in early 2022, which occurred against a backdrop of high two-dose vaccination rates, ongoing roll-out of boosters and paediatric doses, and negligible levels of prior infection. New Omicron subvariants have subsequently emerged with a significant growth advantage over the previously dominant BA.2. We investigated a mathematical model that included waning of vaccine-derived and infection-derived immunity, as well as the impact of the BA.5 subvariant which began spreading in New Zealand in May 2022. The model was used to provide scenarios to the New Zealand Government with differing levels of BA.5 growth advantage, helping to inform policy response and healthcare system preparedness during the winter period. In all scenarios investigated, the projected peak in new infections during the BA.5 wave was smaller than in the first Omicron wave in March 2022. However, results indicated that the peak hospital occupancy was likely to be higher than in March 2022, primarily due to a shift in the age distribution of infections to older groups. We compare model results with subsequent epidemiological data and show that the model provided a good projection of cases, hospitalizations and deaths during the BA.5 wave.
2022 年初，新西兰经历了一波由 SARS-CoV-2 的奥密克戎变异株引起的疫情，当时该国的两剂疫苗接种率很高，加强针和儿科剂量的接种工作正在进行中，且先前的感染率可忽略不计。随后出现了新的奥密克戎亚变种，其相对于之前占主导地位的 BA.2 具有显著的增长优势。我们研究了一个数学模型，该模型考虑了疫苗衍生和感染衍生免疫的衰减，以及 2022 年 5 月在新西兰开始传播的 BA.5 亚变种的影响。该模型用于向新西兰政府提供具有不同 BA.5 增长优势水平的情景，以帮助在冬季期间为政策应对和医疗保健系统的准备提供信息。在所研究的所有情景中，BA.5 波期间新感染的预计峰值均低于 2022 年 3 月的第一波奥密克戎疫情。然而，结果表明，医院占用率的峰值可能高于 2022 年 3 月，主要是由于感染人群的年龄分布向老年群体转移。我们将模型结果与随后的流行病学数据进行了比较，并表明该模型很好地预测了 BA.5 波期间的病例、住院和死亡情况。
