Efficient Immunization Strategies for Computer Networks and Populations

We present an effective immunization strategy for computer networks and populations with broad and, in particular, scale-free degree distributions. The proposed strategy, acquaintance immunization, calls for the immunization of random acquaintances of random nodes (individuals). The strategy requires no knowledge of the node degrees or any other global knowledge, as do targeted immunization strategies. We study analytically the critical threshold for complete immunization. We also study the strategy with respect to the susceptible-infected-removed epidemiological model. We show that the immunization threshold is dramatically reduced with the suggested strategy, for all studied cases.Comment: Revtex, 5 pages, 4 ps fig

Factors Influencing Immunization Status in Primary Care Clinics

Background and Objectives: National standards and goals for childhood immunization rates are well established. Yet, despite clear standards and goals, physicians do not achieve the desired rate (90%) for immunization coverage. This study examined factors related to immunization status for 2-year-old children in pediatric and family practice settings. Methods: Specially trained personnel used computer software to audit 2,552 records from 42 practices in Northeast Florida throughout 1997–1999. Immunization records were judged as either complete or incomplete, and factors related to immunization status were studied. Clinic type and 18 immunization practice standards were reviewed for effect on immunization status. Results: The probability of complete immunization status for children in pediatric clinics was greater than for those in family practice clinics. Multivariate logistic regression revealed that use of semiannual audits (odds ratio [OR]=2.00, confidence interval [CI]=1.65–2.42) was the most important factor for immunization completion. This was followed by availability of discounted immunizations (OR=.44, CI=.27–.73) and the use of an immunization tracking system (OR=1.48, CI=1.18–1.70). Factors that were not found to contribute included clinic type and the remaining 15 practice standards. Conclusions: Considering the significant factors, immunization status was not affected by the type of clinic providing immunizations. Based on this analysis, family physicians should implement tracking systems and should perform semiannual audits to match the success of pediatricians in immunizing children. Neither group met nationally established goals for administration of immunizations for 2-year-old children

Description of Complete Basic Immunization Coverage Among Infant

Immunization coverage in every city/regency must be conducted in accordance with the standard coverage to suppress infectious diseases that can be prevented by vaccination. Temanggung regency is one of the cities/regencies in Central Java Province that have not reached 100% of village universal coverage immunization (UCI). The aim of this study was to determine the coverage of complete basic immunization in infants in Temanggung regency. The design of this study was descriptive observational with quantitative and qualitative approaches. The respondents of the research were parents having babies and the sample size was 520 children. The instrument used was the Rapid Card Check Form recommended by UNICEF. The results showed that there were still infants who had not been immunized. The reasons were that the infants had low birth weight, sick children during immunization, and no support from parents. As the immunization program aims to reduce infant and child mortality, parental awareness is important to increase immunization coverage in Temanggung regency

Immunization of networks with community structure

In this study, an efficient method to immunize modular networks (i.e., networks with community structure) is proposed. The immunization of networks aims at fragmenting networks into small parts with a small number of removed nodes. Its applications include prevention of epidemic spreading, intentional attacks on networks, and conservation of ecosystems. Although preferential immunization of hubs is efficient, good immunization strategies for modular networks have not been established. On the basis of an immunization strategy based on the eigenvector centrality, we develop an analytical framework for immunizing modular networks. To this end, we quantify the contribution of each node to the connectivity in a coarse-grained network among modules. We verify the effectiveness of the proposed method by applying it to model and real networks with modular structure.Comment: 3 figures, 1 tabl

Immunization of complex networks

Complex networks such as the sexual partnership web or the Internet often show a high degree of redundancy and heterogeneity in their connectivity properties. This peculiar connectivity provides an ideal environment for the spreading of infective agents. Here we show that the random uniform immunization of individuals does not lead to the eradication of infections in all complex networks. Namely, networks with scale-free properties do not acquire global immunity from major epidemic outbreaks even in the presence of unrealistically high densities of randomly immunized individuals. The absence of any critical immunization threshold is due to the unbounded connectivity fluctuations of scale-free networks. Successful immunization strategies can be developed only by taking into account the inhomogeneous connectivity properties of scale-free networks. In particular, targeted immunization schemes, based on the nodes' connectivity hierarchy, sharply lower the network's vulnerability to epidemic attacks

Studying the effect of chloroquine on sporozoite-induced protection and immune responses in Plasmodium berghei malaria

BACKGROUND Sporozoite immunization of animals and humans under a chemo-prophylactic cover of chloroquine (CPS-CQ) efficiently induces sterile protection against malaria. In humans, CPS-CQ is strikingly more efficient than immunization with radiation attenuated sporozoites (RAS), raising the hypothesis that this might be partially due to CQ. Chloroquine, an established anti-malarial drug, is also well known for its immune modulating properties including improvement of cross-presentation. The aim of this study was to investigate whether co-administration of CQ during sporozoite immunization improves cellular responses and protective efficacy in Plasmodium berghei models. METHODS A number of experiments in selected complimentary P. berghei murine models in Balb/cByJ and C57BL/6j mice was performed. First, the effect of CQ administration on the induction of protection and immune responses by RAS immunization was studied. Next, the effect of CQ on the induction of circumsporozoite (CS) protein-specific CD8(+) T cells by immunization with P. berghei parasites expressing a mutant CS protein was investigated. Finally, a direct comparison of CPS-CQ to CPS with mefloquine (MQ), an anti-malarial with little known immune modulating effects, was performed. RESULTS When CQ was co-administered during immunization with graded numbers of RAS, this did not lead to an increase in frequencies of total memory CD8(+) T cells or CS protein-specific CD8(+) T cells. Also parasite-specific cytokine production and protection remained unaltered. Replacement of CQ by MQ for CPS immunization resulted in significantly reduced percentages of IFNγ producing memory T cells in the liver (p = 0.01), but similar protection. CONCLUSIONS This study does not provide evidence for a direct beneficial effect of CQ on the induction of sporozoite-induced immune responses and protection in P. berghei malaria models. Alternatively, the higher efficiency of CPS compared to RAS might be explained by an indirect effect of CQ through limiting blood-stage exposure after immunization or to increased antigen exposure and, therefore, improved breadth of the immune response.EMB was supported by Top Institute Pharma (grant T4-102) and KN was supported by the NWO Mozaiek (grant no. 017.005.011)

Immunization of Susceptible-Infected Model on Scale-Free networks

In this paper, we investigate two major immunization strategies, random immunization and targeted immunization, of the susceptible-infected (SI) Model on the Barab\'{a}si-Albert (BA) networks. For the heterogenous structure, the random strategy is quite ineffective if the vaccinated proportion is quite small, while the targeted one which prefers to vaccinate the individuals with the largest degree can sharply depress the epidemic spreading even only a small amount of population are vaccinated. The analytical solution is also obtained,which can capture the trend of velocity change versus the amount of vaccinated population.Comment: 5 pages, 4 figure