On inverse probability-weighted estimators in the presence of interference

We consider inference about the causal effect of a treatment or exposure in the presence of interference, i.e., when one individual’s treatment affects the outcome of another individual. In the observational setting where the treatment assignment mechanism is not known, inverse probability-weighted estimators have been proposed when individuals can be partitioned into groups such that there is no interference between individuals in different groups. Unfortunately this assumption, which is sometimes referred to as partial interference, may not hold, and moreover existing weighted estimators may have large variances. In this paper we consider weighted estimators that could be employed when interference is present. We first propose a generalized inverse probability-weighted estimator and two Hájek-type stabilized weighted estimators that allow any form of interference. We derive their asymptotic distributions and propose consistent variance estimators assuming partial interference. Empirical results show that one of the Hájek estimators can have substantially smaller finite-sample variance than the other estimators. The different estimators are illustrated using data on the effects of rotavirus vaccination in Nicaragua

Effect of Rotavirus Immunization on Childhood Diarrhea in Nicaragua, Research Plan for International Research Scientist Development Award (K01) Fogarty International Center

The impact of universal rotavirus immunization on childhood diarrhea in Nicaragua is unknown. A clear understanding of the magnitude of the effect of UIRI is important information for Nicaragua and other developing world countries who are considering adding rotavirus vaccines to their current vaccine armamentarium. Although preliminary research is measuring the impact of rotavirus immunization in the hospital setting, virtually nothing is known about the effect of UIRI at the primary care or community level. Also, it is not known if genotype shift of the virus is occurring, which could limit the future effectiveness of rotavirus immunization and would inform needed improvements in the vaccine. Finally, we do not know if UIRI is inducing herd immunity. The purpose of this study is to determine the effect of UIRI on diarrheal disease in Nicaragua at the primary care and community levels. Our specific aims are to: 1. Determine the effectiveness of the rotavirus vaccine in primary care clinical practice, using a case-control study. Hypothesis: We expect that UIRI with Rotateq® will have a vaccine effectiveness of about 75% in reducing rotavirus infections that present to primary care centers. 2. Determine the effect of UIRI on diarrhea incidence at the community level, using an existing population-based surveillance system. We will compare incidences prior to UIRI to incidences following UIRI separately for children who did and did not receive the immunization. Hypothesis: Prior hospital-based studies would lead us to expect a one-third reduction in diarrhea incidence among immunized children at the community level. We expect this reduction to be most pronounced during the dry season, when the incidence of rotavirus infection is higher. We expect to find a modest, but measurable reduction in incidence among unimmunized children. 3. Explore if circulating genotypes of the virus have changed following UIRI. We will compare the distribution of rotavirus genotypes prior to UIRI with the distribution following UIRI. Hypothesis: We expect to find a higher percentage of genotypes not covered by the Rotateq® vaccine among immunized children who subsequently develop rotavirus infection. Our analysis of the overall distribution of genotypes following UIRI is exploratory in nature.Master of Public Healt

Hazard of complex regional pain syndrome following human papillomavirus vaccination among adolescent girls in the United States: a case-cohort analysis of insurance claims data

Objectives: Complex regional pain syndrome (CRPS) cases have followed human papillomavirus (HPV) vaccination, but no causal link has been established. Methods: Using insurance claims, the authors observed unvaccinated 11-year-old girls for CRPS diagnoses. The authors used time-dependent Cox regression to identify health-related CRPS predictors using diagnosis codes. Next, the authors identified HPV vaccinations using procedural codes. HPV vaccination and CRPS predictors were considered time-dependent covariates to estimated adjusted hazard ratios (HR) and 95% confidence intervals (CI) for CRPS, 30, 90, and 180-days post-vaccination. Results: 1,232,572 girls received 563 unique CRPS diagnoses. In a 10% sub-cohort of 123,981 girls accounting for potential confounders and predisposing risk factors (i.e. injury, infection, mental illness, primary care use), CRPS hazard was not significantly elevated 30 days (HR: 0.90, 95% CI: 0.46, 1.73), 90 days (HR: 1.17, 95% CI: 0.83, 1.65), or 180-days post-vaccination (HR: 1.11, 95% CI: 0.83, 1.47). Conclusion: The results support the safety and continued administration of HPV vaccines to adolescents

Contribution of Maternal Immunity to Decreased Rotavirus Vaccine Performance in Low- and Middle-Income Countries

ABSTRACT The role of maternal immunity, received by infants either transplacentally or orally from breast milk, in rotavirus vaccine (RV) performance is evaluated here. Breastfeeding withholding has no effect on vaccine responses, but higher levels of transplacental rotavirus-specific IgG antibody contribute to reduced vaccine seroconversion. The gaps in knowledge on the factors associated with low RV efficacy in low- and middle-income countries (LMIC) remain, and further research is needed to shed more light on these issues

Sapovirus: An emerging cause of childhood diarrhea

Purpose of review Sapovirus, a genus in the Caliciviridae family alongside norovirus, is increasingly recognized as an important cause of childhood diarrhea. Some challenges exist in our ability to better understand sapovirus infections, including the inability to grow sapovirus in cell culture, which has hindered diagnosis and studies of immunity. Another challenge is that individuals with sapovirus infection are commonly coinfected with other enteric pathogens, complicating our ability to attribute the diarrhea episode to a single pathogen. Recent findings Development of molecular methods for sapovirus detection has increased our ability to measure disease prevalence. The prevalence of sapovirus varies between 1 and 17% of diarrhea episodes worldwide, with the highest burden in young children and older adults. Further, epidemiological studies have used novel approaches to account for the presence of coinfections with other enteric pathogens; one multisite cohort study of children under two years of age found that sapovirus had the second-highest attributable incidence among all diarrheal pathogens studied. Summary Especially in settings where rotavirus vaccines have been introduced, efforts to reduce the overall burden of childhood diarrhea should focus on the reduction of sapovirus transmission and disease burden

Sapovirus: an important cause of acute gastroenteritis in children

Sapovirus infections are responsible for both sporadic cases and occasional outbreaks of acute gastroenteritis. While all age groups are affected, children younger than five years of age have the highest burden of disease. Sharing many similarities with closely-related noroviruses, common symptoms of sapovirus gastroenteritis include vomiting and diarrhea, which typically resolve within one week.1 Sapovirus has also been detected in asymptomatic individual

Rotavirus Vaccine Schedules and Vaccine Response Among Infants in Low- and Middle-Income Countries: A Systematic Review

Rotavirus vaccine schedules may impact vaccine response among children in low- and middle-income countries (LMICs). Our objective was to review the literature evaluating the effects of monovalent (RV1) or pentavalent rotavirus vaccines schedules on vaccine response

Patterns of Use of Human Papillomavirus and Other Adolescent Vaccines in the United States

AbstractPurposeThe purpose of the study was to describe the patterns of use of universally recommended adolescent vaccines in the United States.MethodsWe identified 11-year-olds using the MarketScan insurance claims database (2009–2014). Human papillomavirus (HPV), tetanus-diphtheria-acellular pertussis (Tdap), and meningococcal (MenACWY) vaccination claims were identified using diagnosis and procedure codes. Generalized linear models estimated vaccination incidence rates and correlates of adolescent vaccination and timely vaccination.ResultsAmong 1,691,223 adolescents, receipt of Tdap (52.1%) and MenACWY (45.8%) vaccinations exceeded receipt of HPV vaccination (18.4%). While both sexes had similar Tdap and MenACWY vaccination proportions, girls received HPV vaccination more frequently than boys (21.9% vs. 15.1%). Adolescents received HPV vaccination later (mean age: 11.8 years) than Tdap or MenACWY vaccination (mean age: 11.2 years for both). Half of vaccinated adolescents received Tdap and MenACWY vaccination only; however, coadministration with HPV vaccine increased with birth cohort. Western adolescents had the highest incidence rates of HPV vaccination, and Southern adolescents had the lowest. Rural adolescents were less likely than urban adolescents to receive each vaccination except in the Northeast, where they were more likely to receive HPV vaccination (incidence rate ratio: 1.09, 95% confidence interval: 1.2005–1.13). Timely HPV vaccination was associated with female sex, urbanicity, Western residence, and later birth cohort.ConclusionsHPV vaccination occurred later than Tdap or MenACWY vaccination and was less frequent in boys and rural adolescents. Girls, Western and urban residents, and younger birth cohorts were more likely to receive timely HPV vaccination. Vaccine coadministration increased over time and may encourage timely and complete vaccination coverage

Cost-Effectiveness of Adding Bed Net Distribution for Malaria Prevention to Antenatal Services in Kinshasa, Democratic Republic of the Congo

We evaluated the cost-effectiveness of distributing insecticide-treated bed nets (ITNs) for malaria prevention at antenatal clinics in Kinshasa, Democratic Republic of the Congo. A decision tree model was used to estimate costs, outcomes, and incremental cost-effectiveness for 17,893 pregnant women attending 28 antenatal clinics who received long-lasting ITNs free of charge. Costs including purchase, transportation, storage, and distribution of ITNs were derived from program records. The ITN efficacy and other parameters were derived from peer-reviewed literature. Outcomes modeled included low birth weight (LBW) deliveries, infant deaths averted, life-years saved (LYs), and disability-adjusted life-years (DALYs) averted. Deterministic and probabilistic sensitivity analyses were conducted. For the 17,893 women in our program, ITN distribution would be expected to avert 587 LBW deliveries and 414 infant deaths. The incremental cost-effectiveness was US $17.22 per DALY averted (95$8.54-$30.90), US$15.70 per LY saved (95% CI = US $7.65-$27.68), and US $411.13 per infant death averted (95$353.95-$1,085.89). If resources were constrained, the greatest benefit would be among women in their first through fourth pregnancies. Thus, ITN distribution is a cost-effective addition to antenatal services