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1. Bias in the estimated reporting fraction due to vaccination in the time-series SIR model

   https://doi.org/10.1371/journal.pone.0330568  

   Leung, Tiffany; Ferrari, Matthew (August 2025, PLOS One)

   Rychtář, Jan (Ed.)

   The time-series Susceptible-Infectious-Recovered (TSIR) model has been a standard tool for studying the non-linear dynamics of acute, immunizing infectious diseases. The standard assumption of the TSIR model, that vaccination is equivalent to a reduction in the recruitment of susceptible individuals, or the birth rate, can lead to a bias in the estimate of the reporting fraction and of the total incidence. We show that this bias increases with the level of vaccination due to a double counting of individuals who are infected prior to the age of vaccination. We present a simple correction for this bias by discounting the observed number of cases by the product of the number that occur prior to the average age of vaccination and the vaccination coverage during the initial susceptible reconstruction step of the TSIR model fitting. We generate a time series of measles cases using an age-structured SIR transmission model with vaccination after birth (at 9 months of age) and illustrate the bias with the standard TSIR fitting method. We then illustrate that our proposed correction eliminates the bias in the estimated reporting fraction and total incidence. We note further that this bias does not impact the estimates of the seasonality of transmission. 

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2. Evaluating vaccination policies to accelerate measles elimination in China: a meta-population modelling study

   https://doi.org/10.1093/ije/dyz058  

   Hao, Lixin; Glasser, John W; Su, Qiru; Ma, Chao; Feng, Zhilan; Yin, Zundong; Goodson, James L; Wen, Ning; Fan, Chunxiang; Yang, Hong; et al (April 2019, International Journal of Epidemiology)

   Abstract Background Measles is among the most highly infectious human diseases. By virtue of increasingly effective childhood vaccination, together with targeted supplemental immunization activities (SIAs), health authorities in the People’s Republic of China have reduced measles’ reproduction number from about 18 to 2.3. Despite substantial residual susceptibility among young adults, more in some locales than others, sustained routine childhood immunization likely would eliminate measles eventually. To support global eradication efforts, as well as expedite morbidity and mortality reductions in China, we evaluated alternative SIAs via mechanistic mathematical modelling. Methods Our model Chinese population is stratified by immune status (susceptible to measles infection; infected, but not yet infectious; infectious; and recovered or immunized), age (0, 1–4, 5–9, …, 65+ years) and location (31 provinces). Contacts between sub-populations are either empirical or a mixture of preferential and proportionate with respect to age and decline exponentially with distance between locations at age-dependent rates. We estimated initial conditions and most parameters from recent cross-sectional serological surveys, disease surveillance and demographic observations. Then we calculated the reproduction numbers and gradient of the effective number with respect to age- and location-specific immunization rates. We corroborated these analytical results by simulating adolescent and young adult SIAs using a version of our model in which the age-specific contact rates vary seasonally. Results Whereas the gradient indicates that vaccinating young adults generally is the optimal strategy, simulations indicate that a catch-up campaign among susceptible adolescent schoolchildren would accelerate elimination, with timing dependent on uptake. Conclusions These results are largely due to indirect effects (i.e. fewer infections than immunized people might otherwise cause), which meta-population models with realistic mixing are uniquely capable of reproducing accurately. 

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3. A Game-Theoretic Model of Voluntary Yellow Fever Vaccination to Prevent Urban Outbreaks

   https://doi.org/10.3390/g13040055  

   Caasi, Jovic Aaron; Joseph, Brian M.; Kodiyamplakkal, Heera J.; Manibusan, Jaelene Renae; Camacho Aquino, Leslie J.; Oh, Hyunju; Rychtář, Jan; Taylor, Dewey (August 2022, Games)

   Yellow fever is a vector-borne acute viral hemorrhagic disease. It is endemic in tropical areas of Africa and Latin America but demonstrated the potential for international spread during the 2016 outbreak in Luanda, Angola. Yellow fever can be prevented by vaccination, vector control, and avoiding mosquito bites. To account for human behavior in disease dynamics, we add a game-theoretic component to a recent compartmental model of yellow fever transmission. The self-interested individuals evaluate the risks of contracting yellow fever and choose to vaccinate or avoid the bites to minimize the overall costs. We find the Nash equilibria, the optimal levels of vaccination and bite protections if the individuals can decide on the use of only one of the prevention methods as well as when they can decide on the use of both of them. In the later case, we show that vaccination is the preferred method of protection from the individual standpoint and, in the Nash equilibrium, individuals use vaccination only. Our model predicts the vaccination coverage in Angola to be around 65%, which is in reasonable agreement with the empirical value of 68%. We also study whether voluntary prevention can lead to the elimination of the disease in endemic areas. We show that voluntary vaccination alone is not enough to mitigate the risks of outbreaks, suggesting that a mandatory vaccination policy is necessary. 

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4. Which nursing home workers were at highest risk for SARS-CoV-2 infection during the November 2020–February 2021 winter surge of COVID-1?

   https://doi.org/10.1017/ash.2022.66  

   Kellogg, Joseph; Dube, William; Adams, Carly; Collins, Matthew; Lopman, Theodore; Johnson, Theodore; Amin, Avnika; Weitz, Joshua; Fridkin, Scott (July 2022, Antimicrobial Stewardship & Healthcare Epidemiology)

   Background: Nursing home (NH) residents and staff were at high risk for COVID-19 early in the pandemic; several studies estimated seroprevalence of infection in NH staff to be 3-fold higher among CNAs and nurses compared to other staff. Risk mitigation added in Fall 2020 included systematic testing of residents and staff (and furlough if positive) to reduce transmission risk. We estimated risks for SARS-CoV-2 infection among NH staff during the first winter surge before widespread vaccination. Methods: Between February and May 2021, voluntary serologic testing was performed on NH staff who were seronegative for SARS-CoV-2 in late Fall 2020 (during a previous serology study at 14 Georgia NHs). An exposure assessment at the second time point covered prior 3 months of job activities, community exposures, and self-reported COVID-19 vaccination, including very recent vaccination (≤4 weeks). Risk factors for seroconversion were estimated by job type using multivariable logistic regression, accounting for interval community-incidence and interval change in resident infections per bed. Results: Among 203 eligible staff, 72 (35.5%) had evidence of interval seroconversion (Fig. 1). Among 80 unvaccinated staff, interval infection was significantly higher among CNAs and nurses (aOR, 4.9; 95% CI, 1.4–20.7) than other staff, after adjusting for race and interval community incidence and facility infections. This risk persisted but was attenuated when utilizing the full study cohort including those with very recent vaccination (aOR, 1.8; 95% CI, 0.9–3.7). Conclusions : Midway through the first year of the pandemic, NH staff with close or common resident contact continued to be at increased risk for infection despite enhanced infection prevention efforts. Mitigation strategies, prior to vaccination, did not eliminate occupational risk for infection. Vaccine utilization is critical to eliminate occupational risk among frontline healthcare providers. Funding: None Disclosures: None 

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5. Usability testing with teens: Adapting human-centered design and UX methods

   https://doi.org/10.1145/3233756.3233955  

   Rose, Emma J.; Björling, Elin A.; Kim, Ada; Alvarez, Nicole Young (January 2018, Proceedings of The 36th ACM International Conference on the Design of Communication)

   Teens are a unique population with needs and communication styles that differ from adults and children. Methods in humancentered design were initially conceptualized with adults in mind, but these methods should be reexamined to include the needs of teens. In this experience report, we reflect on a project introducing teens to human-centered design and methods. As part of the project, our team created a website and series of videos. We conducted a usability evaluation on the videos and an accompanying website with teens to understand what worked well and how to make improvements. In this report, we discuss how we modified traditional usability methods and tailored them for a teen audience. We share takeaways including keep methods and tools lightweight and facilitation styles engaging and casual. We assert that modifying methods is a key consideration for conducting usability testing with any unique group of users. 

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