Basque Center for Applied Mathematics (BCAM), Bilbao, Spain; Dipartimento di Matematica, Università degli Studi di Trento, Italy; Ikerbasque, Basque Foundation for Science, Bilbao, Spain.
Public Health, Basque Health Department, Rekalde Zumarkalea 39A - 48008, Bilbao, Spain.
J Adv Res. 2022 Jul;39:157-166. doi: 10.1016/j.jare.2021.10.012. Epub 2021 Nov 16.
Different COVID-19 vaccine efficacies are reported, with remarkable effectiveness against severe disease. The so called sterilizing immunity, occurring when vaccinated individuals cannot transmit the virus, is still being evaluated. It is also unclear to what extent people with no symptoms or mild infection transmit the disease, and estimating their contribution to outbreaks is challenging.
With an uneven roll out of vaccination, the purpose of this study is to investigate the role of mild and asymptomatic infections on COVID-19 vaccine performance as vaccine efficacy and vaccine coverage vary.
We use an epidemiological SHAR (Susceptible-Hospitalized-Asymptomatic-Recovered) model framework to evaluate the effects of vaccination in different epidemiological scenarios of coverage and efficacy. Two vaccination models, the vaccine V protecting against severe disease, and the vaccine V, protecting against infection as well as severe disease, are compared to evaluate the reduction of overall infections and hospitalizations.
Vaccine performance is driven by the ability of asymptomatic or mild disease cases transmitting the virus. Vaccines protecting against severe disease but failing to block transmission might not be able to reduce significantly the severe disease burden during the initial stage of a vaccination roll out programme, with an eventual increase on the number of overall infections in a population.
The different COVID-19 vaccines currently in use have features placing them closer to one or the other of these two extreme cases, V and V, and insights on the importance of asymptomatic infection in a vaccinated population are of a major importance for the future planning of vaccination programmes. Our results give insights on how to best combine the use of the available COVID-19 vaccines, optimizing the reduction of hospitalizations.
不同的 COVID-19 疫苗具有不同的功效，对严重疾病有显著的效果。所谓的“绝育免疫”，即接种疫苗的人无法传播病毒，目前仍在评估中。无症状或轻度感染的人在多大程度上传播疾病也不清楚，估计他们对疫情爆发的贡献具有挑战性。
由于疫苗接种进展不平衡，本研究旨在调查轻度和无症状感染在 COVID-19 疫苗性能中的作用，因为疫苗效力和疫苗覆盖率存在差异。
我们使用流行病学 SHAR（易感-住院-无症状-恢复）模型框架来评估在不同的疫苗覆盖率和效力的流行病学情况下接种疫苗的效果。我们比较了两种疫苗模型，即 V 疫苗预防严重疾病，以及 V 疫苗预防感染和严重疾病，以评估对总体感染和住院的减少效果。
疫苗的性能取决于无症状或轻度疾病病例传播病毒的能力。不能阻止传播但能预防严重疾病的疫苗在疫苗接种计划的初始阶段可能无法显著减少严重疾病负担，最终会导致人群中总体感染人数增加。
目前使用的不同 COVID-19 疫苗具有接近这两种极端情况（V 和 V）的特征，对已接种人群中无症状感染的重要性的认识对未来疫苗接种计划的规划具有重要意义。我们的研究结果提供了如何最好地结合使用现有 COVID-19 疫苗的见解，以优化住院人数的减少。
