Background Knowledge of SARS-CoV-2 household transmission dynamics guides infection control and vaccination measures. This household cohort study prospectively assessed the impact of both the Omicron BA.2 variant and immunity on household transmission using dense saliva sampling and sequence analysis. Methods Households consisting of a PCR-confirmed index and at least two household members were enrolled in March and April 2022 during the Omicron BA.2 wave in the Netherlands. SARS-CoV-2 PCR was performed on ten consecutive saliva samples. Serum-antibodies were measured at baseline and day 42. Household and per-person Secondary Attack Rate (SAR) were calculated to measure transmission. Whole genome sequencing was performed for phylogenetic analysis, followed by sensitivity analysis, to correct for multiple household introductions and index definition. Results were compared with the identical, early-pandemic, pre-immunisation predecessor study. Results Sixty-seven households were included, consisting of 241 individuals (median age 33.0 years (IQR 12.0-46.0)). Maximum household SAR was 59.7%, per-person SAR 41.5%. Paediatric index cases were more likely to transmit. Transmission was negatively affected by household members’ immunity. Phylogenetic analysis showed multiple introductions in four households. Sensitivity analysis resulted in a minimal household SAR of 51.0% and per-person SAR of 28.5%. Conclusions The Omicron BA.2 variant is highly transmissible within households. However, the transmission rate is lower compared to previous studies with other SARS-CoV-2 variants, highlighting the effect of immunity. Regardless of immune status, children have a crucial role in Omicron household transmission. Intensive sampling and phylogenetic analysis are beneficial for correctly calculating transmission rates, especially during periods of minimal behavioural restrictions.

中文翻译：

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与野生型相比，SARS-CoV-2 VOC Omicron 的家庭传播水平较低：传播性和免疫状态之间的相互作用


背景 SARS-CoV-2 家庭传播动态的知识指导感染控制和疫苗接种措施。这项家庭队列研究使用密集唾液采样和序列分析前瞻性评估了 Omicron BA.2 变体和免疫力对家庭传播的影响。方法 在 2022 年 3 月和 4 月荷兰 Omicron BA.2 浪潮期间，由一个 PCR 确认指数和至少两名家庭成员组成的家庭被登记。对 10 个连续的唾液样本进行 SARS-CoV-2 PCR。在基线和第 42 天测量血清抗体。计算家庭和每人二次发作率 （SAR） 以衡量传播情况。进行全基因组测序进行系统发育分析，然后进行敏感性分析，以纠正多个家庭介绍和指数定义。将结果与相同的、大流行早期、免疫接种前的研究进行了比较。结果 共纳入 67 个家庭，共 241 人 （中位年龄 33.0 岁 （IQR 12.0-46.0））。最高住户 SAR 为 59.7%，人均 SAR 为 41.5%。儿科指示病例更有可能传播。传播受到家庭成员免疫力的负面影响。系统发育分析显示 4 个家庭的多次引入。敏感性分析得出的最小家庭 SAR 为 51.0%，人均 SAR 为 28.5%。结论 Omicron BA.2 变体在家庭中具有高度传播性。然而，与之前对其他 SARS-CoV-2 变体的研究相比，传播率较低，突出了免疫力的作用。无论免疫状况如何，儿童在 Omicron 家庭传播中都起着至关重要的作用。 密集采样和系统发育分析有利于正确计算传播率，尤其是在行为限制最小期间。