The evolutionary language game: an orthogonal approach

Evolutionary game dynamics have been proposed as a mathematical framework for the cultural evolution of language and more specifically the evolution of vocabulary. This article discusses a model that is mutually exclusive in its underlying principals with some previously suggested models. The model describes how individuals in a population culturally acquire a vocabulary by actively participating in the acquisition process instead of passively observing and communicate through peer-to-peer interactions instead of vertical parent-offspring relations. Concretely, a notion of social/cultural learning called the naming game is first abstracted using learning theory. This abstraction defines the required cultural transmission mechanism for an evolutionary process. Second, the derived transmission system is expressed in terms of the well-known selection-mutation model defined in the context of evolutionary dynamics. In this way, the analogy between social learning and evolution at the level of meaning-word associations is made explicit. Although only horizontal and oblique transmission structures will be considered, extensions to vertical structures over different genetic generations can easily be incorporated. We provide a number of simplified experiments to clarify our reasoning.     

Decentralized resource allocation to control an epidemic: A game theoretic approach

This paper examines how two countries would allocate resources at the onset of an epidemic when they seek to protect their own populations by minimizing the total number of infectives over the entire time horizon. We model this situation as a game between selfish countries, where players strategically allocate their resources in order to minimize the total number of infected individuals in their respective populations during the epidemic. We study this problem when the initial number of infectives is very small, which greatly simplifies the analysis. We show in this framework that selfish countries always allocate their resources so as to bring the effective reproduction ratio below one and avoid a major outbreak. When a major outbreak is avoidable, we further identify the necessary and sufficient conditions under which the individual allocation decisions of selfish countries match the decision that a central planner would make in order to minimize the total number of infectives in the whole population (without distinguishing between countries).     

Seasonal influenza vaccination campaigns for health care personnel: systematic review

Background

In Canada, vaccination coverage for seasonal influenza among health care personnel remains below 50%. The objective of this review was to determine which seasonal influenza vaccination campaign or campaign components in health care settings were significantly associated with increases in influenza vaccination among staff.

Methods

We identified articles in eight electronic databases and included randomized controlled trials, controlled before-and-after studies and studies with interrupted time series designs in our review. Two reviewers independently abstracted the data and assessed the risk of biases. We calculated risk ratios and 95% confidence intervals for randomized controlled trials and controlled before-and-after studies and described interrupted time series studies.

Results

We identified 99 studies evaluating influenza vaccination campaigns for health care workers, but only 12 of the studies were eligible for review. In nonhospital health care settings, including long-term care facilities, campaigns with a greater variety of components (including education or promotion, better access to vaccines, legislation or regulation and/or role models) were associated with higher risk ratios (i.e, favouring the intervention group). Within hospital settings, the results reported for various types of campaigns were mixed. Many of the criteria for assessing risk of bias were not reported.

Interpretation

Campaigns involving only education or promotion resulted in minimal changes in vaccination rates. Further studies are needed to determine the appropriate components and combinations of components in influenza vaccination campaigns for health care personnel.Health care personnel can act as vectors of influenza and may transmit the disease to patients who are at risk for influenza-related complications or death.¹ A Cochrane review² of three studies showed that vaccination of health care personnel, combined with vaccination of patients, was 86% efficacious (95% confidence interval [CI] 40%–97%) in preventing influenza-like illnesses among elderly patients. It is recommended that all health care personnel (i.e., minimum 90% coverage) receive the seasonal influenza vaccine for protection from the virus.³Rates of vaccination against seasonal influenza among health care personnel are often below targeted levels and vary across health care organizations in Canada and internationally. In 2003, vaccination coverage was 46% among Canadians employed in ambulatory care settings, hospitals and long-term care facilities.⁴ In a survey of Canadian long-term care facilities, the average vaccination rate among workers was 35%.⁵ Similarly, in the United States, vaccination coverage for health care personnel was about 40%,⁶ and in European countries, reported vaccine uptake has ranged from 14% to 48%.⁷The Canadian National Advisory Committee on Immunization encourages all organizations to actively promote the influenza vaccine and to provide education aimed at health care personnel.³ The US Healthcare Infection Control Practices Advisory Committee and the Advisory Committee on Immunization Practices have recommended that all organizations employing health care personnel use evidence-based approaches that may overcome barriers to vaccine uptake as part of their influenza vaccination campaigns.⁶ These two committees identified five categories of components of influenza vaccination campaigns aimed at improving immunization rates among health care personnel (6

Critical comparison of multidimensional separation methods for increasing protein expression coverage

We present a comparison of two-dimensional separation methods and how they affect the degree of coverage of protein expression in complex mixtures. We investigated the relative merits of various protein and peptide separations prior to acidic reversed-phase chromatography directly coupled to an ion trap mass spectrometer. The first dimensions investigated were density gradient organelle fractionation of cell extracts, 1D SDS-PAGE protein separation followed by digestion by trypsin or GluC proteases, strong cation exchange chromatography, and off-gel isoelectric focusing of tryptic peptides. The number of fractions from each first dimension and the total data accumulation RP-HPLC-MS/MS time was kept constant and the experiments were run in triplicate. We find that the most critical parameters are the data accumulation time, which defines the level of under-sampling and the avoidance of peptides from high expression level proteins eluting over the entire gradient.     

A model for influenza with vaccination and antiviral treatment

Compartmental models for influenza that include control by vaccination and antiviral treatment are formulated. Analytic expressions for the basic reproduction number, control reproduction number and the final size of the epidemic are derived for this general class of disease transmission models. Sensitivity and uncertainty analyses of the dependence of the control reproduction number on the parameters of the model give a comparison of the various intervention strategies. Numerical computations of the deterministic models are compared with those of recent stochastic simulation influenza models. Predictions of the deterministic compartmental models are in general agreement with those of the stochastic simulation models.     

Finding optimal vaccination strategies for pandemic influenza using genetic algorithms

In the event of pandemic influenza, only limited supplies of vaccine may be available. We use stochastic epidemic simulations, genetic algorithms (GA), and random mutation hill climbing (RMHC) to find optimal vaccine distributions to minimize the number of illnesses or deaths in the population, given limited quantities of vaccine. Due to the non-linearity, complexity and stochasticity of the epidemic process, it is not possible to solve for optimal vaccine distributions mathematically. However, we use GA and RMHC to find near optimal vaccine distributions. We model an influenza pandemic that has age-specific illness attack rates similar to the Asian pandemic in 1957-1958 caused by influenza A(H2N2), as well as a distribution similar to the Hong Kong pandemic in 1968-1969 caused by influenza A(H3N2). We find the optimal vaccine distributions given that the number of doses is limited over the range of 10-90% of the population. While GA and RMHC work well in finding optimal vaccine distributions, GA is significantly more efficient than RMHC. We show that the optimal vaccine distribution found by GA and RMHC is up to 84% more effective than random mass vaccination in the mid range of vaccine availability. GA is generalizable to the optimization of stochastic model parameters for other infectious diseases and population structures.     

Universal influenza vaccination: the time to act is now

Annual influenza epidemics create a significant public health burden each year in the United States. That influenza continues to pose a public health threat despite being largely preventable through vaccination is indicative of continuing weaknesses in the U.S.'s public health system. Moreover, the burden of annual influenza epidemics and the fragility and instability of the capacity to respond to them underscore the U.S.'s ongoing vulnerability to pandemic influenza and highlights gaps in bioterrorism preparedness and response efforts. This article examines the burden of annual influenza epidemics in the U.S., efforts to combat that burden with vaccination, shortcomings of influenza vaccination efforts, and how those shortcomings exemplify weaknesses in pandemic influenza and bioterrorism preparedness efforts. We make the case for establishing an annual universal influenza vaccination program to assure access to influenza vaccination to anyone who can safely receive vaccination and desires it. Such a program could greatly reduce the annual burden of influenza while advancing and maintaining U.S. pandemic influenza and bioterrorism preparedness and response efforts.     

Vaginal mucosa serves as an inductive site for tolerance

These data demonstrate that tolerance can be induced by vaginal Ag exposure. In these experiments, mice were given vaginal agarose gel suppositories containing either 5 mg OVA or saline for 6 h. Mice were given suppositories either during the estrous (estrogen dominant) or diestrous (progesterone dominant) stage of the estrous cycle. Mice were restrained during the inoculation period to prevent orovaginal transmission of the Ag. After 1 wk, mice were immunized s. c. with OVA in CFA. After 3 wk, mice were tested for delayed-type hypersensitivity responses by measuring footpad swelling and measuring in vitro proliferation of lymphocytes to Ag. Using ELISA, the magnitude of the serum Ab response was also measured. In some mice, FITC conjugated to OVA was used to track the dissemination of the protein into the systemic tissues. The magnitude of footpad swelling was significantly reduced in mice receiving OVA-containing suppositories during estrus compared with mice receiving saline suppositories. Concomitant decreases in the Ag-specific proliferative response were also observed in lymph node lymphocytes and splenocytes. Conversely, mice inoculated during diestrus did not show a decreased response to Ag by either footpad response or in vitro proliferation. Serum Ab titers in the estrus-inoculated mice did not decrease significantly. These data demonstrate that the reproductive tract can be an inductive site for mucosally induced tolerance. However, unlike other mucosal sites such as the lung and gastrointestinal tract, reproductive tract tolerance induction is hormonally regulated.