Since diffusion models of social network are widely used in studying epidemiology, in this thesis, we apply diffusion models to study the contact immunity generated by attenuated vaccines.Oral polio vaccine (OPV) is a typical attenuated vaccine for polio that can produce contact immunity and therefore help protect more individuals than vaccinees. / To better capture the utilization of OPV’s contact immunity, we model the community as a social network, and formulate the task of maximizing the contact immunity effect as an optimization problem on graphs, which is to find a sequence of vertices to be “vaccinated” to maximize the total number of vertices “infected” by the attenuated virus. Furthermore, as immune defiicient patients may suffer from the live attenuated virus in the vaccine, we develop models in consideration of this restriction, and study related problems. / We present polynomial-time algorithms for these problems on trees, and show the intractability of problems on general graphs. / 社交網絡的擴散模型被廣泛運用于對流行病學的研究，在本文中，我們使用擴散模型對減毒活疫苗產生的接觸性免疫進行研究。口服脊髓灰質炎疫苗（OPV）是一種典型的減毒活疫苗，它可以在人群中產生接觸性免疫，使得更多未接種疫苗的人獲得免疫力。 / 爲了更好的刻畫OPV 產生的接觸性免疫，我們將社區模型化為社交網絡，從而將接觸性免疫效應最大化的任務轉化爲圖優化問題，即通過發現頂點的一個「接種」序列來最大化被減活病毒「感染」的頂點數量。此外，因爲減毒疫苗中的活病毒會使患有免疫缺陷的病人患病，我們考慮在此因素限制下的模型，并研究相關的問題。 / 我們給出這些問題在樹上的多項式時間算法，并證明其在一般圖上的複雜性。 / Ma, Chenglong. / Thesis M.Phil. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 40-47). / Abstracts also in Chinese. / Title from PDF title page (viewed on 12, September, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

This thesis offers a detailed account of early polio epidemics (between 1918 and 1945) in Johannesburg, where the disease was particularly severe. At this time, little was known about the poliovirus, and such limited understanding affected the public health and medical initiatives taken during this period. These actions are highlighted in the thesis, along with the responses of the media and lay public to the disease. The effect of war on the management of the disease is also examined, as it siphoned off vital medical personnel and jeopardised disease control. It also lent an emotional overlay to the way the disease was perceived, as `battle' rhetoric became the parlance used against polio, which was personified as the `enemy' of innocent children who were disabled at the whim of the virus. The epidemic of 1944-1945 was the first to be systematically investigated, by Dr James Gear as part of his groundbreaking polio research; he later became part of an international team of researchers who contributed to the development of a prophylactic vaccine within a decade of this epidemic. / History / M.A. (History)

This thesis offers a detailed account of early polio epidemics (between 1918 and 1945) in Johannesburg, where the disease was particularly severe. At this time, little was known about the poliovirus, and such limited understanding affected the public health and medical initiatives taken during this period. These actions are highlighted in the thesis, along with the responses of the media and lay public to the disease. The effect of war on the management of the disease is also examined, as it siphoned off vital medical personnel and jeopardised disease control. It also lent an emotional overlay to the way the disease was perceived, as `battle' rhetoric became the parlance used against polio, which was personified as the `enemy' of innocent children who were disabled at the whim of the virus. The epidemic of 1944-1945 was the first to be systematically investigated, by Dr James Gear as part of his groundbreaking polio research; he later became part of an international team of researchers who contributed to the development of a prophylactic vaccine within a decade of this epidemic. / History / M.A. (History)