Department of Nursing, School of Health Sciences, Hellenic Mediterranean University, Crete, Greece.
Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
Infect Dis (Lond). 2022 Mar;54(3):186-195. doi: 10.1080/23744235.2021.1995627. Epub 2021 Nov 7.
Understanding the factors that affect the transmissibility of SARS-CoV-2 remains important to keep transmission low and maximize the health benefits of vaccination. We assessed the factors associated with the transmissibility of SARS-CoV-2 based on contact tracing data.
From 1 October to 9 December 2020, 29,385 laboratory-confirmed SARS-CoV-2 cases (index cases, i.e. the first identified laboratory-confirmed cases or with the earliest symptom onset in a setting) and 64,608 traced contacts were identified in Greece. We assessed the prevalence of symptoms in cases, calculated secondary attack rates and assessed factors associated with infectivity and susceptibility to infection.
There were 11,232 contacts secondarily infected (secondary attack rate: 17.4%, 95% CI:17.0-17.8). Contacts aged 0-11 and 12-17 years were less susceptible to infection than adults 65 years or older (odds ratio (OR) [95% CI]: 0.28 [0.26-0.32] and 0.44 [0.40-0.49], respectively). Index cases aged 65 years or older were more likely to infect their contacts than other adults or children/adolescents. The odds of infection [95% CI] were higher in contacts exposed within the household (1.71 [1.59-1.85] vs. other) and in cases with cough (1.17 [1.11-1.25] vs. no cough). There was an interaction between the age of the index and the age of the contact with contacts 65 years or older having a higher probability of infection when exposed to cases of similar age than to children.
Our findings highlight the role of age and age mixing in infectivity and susceptibility to SARS-CoV-2 infection. Precautions are necessary for individuals 65 or older as they have higher infectivity and susceptibility in contact with their peers.
了解影响 SARS-CoV-2 传播力的因素对于保持低传播率和最大限度地提高疫苗接种的健康效益仍然很重要。我们根据接触者追踪数据评估了与 SARS-CoV-2 传播力相关的因素。
2020 年 10 月 1 日至 12 月 9 日，在希腊共发现 29385 例实验室确诊的 SARS-CoV-2 病例（索引病例，即第一个确诊的实验室病例或在特定环境中最早出现症状的病例）和 64608 例追踪到的接触者。我们评估了病例中症状的流行率，计算了二级攻击率，并评估了与传染性和易感性相关的因素。
共有 11232 名接触者继发感染（二级攻击率：17.4%，95%CI：17.0-17.8）。0-11 岁和 12-17 岁的接触者比 65 岁及以上的成年人更不易感染（比值比（OR）[95%CI]：0.28 [0.26-0.32]和 0.44 [0.40-0.49]）。65 岁及以上的索引病例更有可能感染其接触者，而不是其他成年人或儿童/青少年。与其他接触者相比，在家庭内接触（1.71 [1.59-1.85] vs. 其他）和病例有咳嗽（1.17 [1.11-1.25] vs. 无咳嗽）的接触者感染的可能性更高。索引病例的年龄与接触者的年龄之间存在交互作用，与儿童相比，与年龄相仿的病例接触时，65 岁及以上的接触者感染的可能性更高。
我们的研究结果强调了年龄和年龄混合在 SARS-CoV-2 感染的传染性和易感性中的作用。对于 65 岁及以上的个体，需要采取预防措施，因为他们在与同龄人接触时具有更高的传染性和易感性。
