Reactive Vaccination Research Articles

Projecting vaccine demand and impact for emerging zoonotic pathogens

BackgroundDespite large outbreaks in humans seeming improbable for a number of zoonotic pathogens, several pose a concern due to their epidemiological characteristics and evolutionary potential. To enable effective responses to these pathogens in the event that they undergo future emergence, the Coalition for Epidemic Preparedness Innovations is advancing the development of vaccines for several pathogens prioritized by the World Health Organization. A major challenge in this pursuit is anticipating demand for a vaccine stockpile to support outbreak response.MethodsWe developed a modeling framework for outbreak response for emerging zoonoses under three reactive vaccination strategies to assess sustainable vaccine manufacturing needs, vaccine stockpile requirements, and the potential impact of the outbreak response. This framework incorporates geographically variable zoonotic spillover rates, human-to-human transmission, and the implementation of reactive vaccination campaigns in response to disease outbreaks. As proof of concept, we applied the framework to four priority pathogens: Lassa virus, Nipah virus, MERS coronavirus, and Rift Valley virus.ResultsAnnual vaccine regimen requirements for a population-wide strategy ranged from > 670,000 (95% prediction interval 0–3,630,000) regimens for Lassa virus to 1,190,000 (95% PrI 0–8,480,000) regimens for Rift Valley fever virus, while the regimens required for ring vaccination or targeting healthcare workers (HCWs) were several orders of magnitude lower (between 1/25 and 1/700) than those required by a population-wide strategy. For each pathogen and vaccination strategy, reactive vaccination typically prevented fewer than 10% of cases, because of their presently low R0 values. Targeting HCWs had a higher per-regimen impact than population-wide vaccination.ConclusionsOur framework provides a flexible methodology for estimating vaccine stockpile needs and the geographic distribution of demand under a range of outbreak response scenarios. Uncertainties in our model estimates highlight several knowledge gaps that need to be addressed to target vulnerable populations more accurately. These include surveillance gaps that mask the true geographic distribution of each pathogen, details of key routes of spillover from animal reservoirs to humans, and the role of human-to-human transmission outside of healthcare settings. In addition, our estimates are based on the current epidemiology of each pathogen, but pathogen evolution could alter vaccine stockpile requirements.

Reactive vaccination as control strategy for an outbreak of invasive meningococcal disease caused by Neisseria meningitidis C:P1.5-1,10-8:F3-6:ST-11(cc11), Bergamo province, Italy, December 2019 to January 2020

In Italy, serogroup C meningococci of the clonal complex cc11 (MenC/cc11) have caused several outbreaks of invasive meningococcal disease (IMD) during the past 20 years. Between December 2019 and January 2020, an outbreak of six cases of IMD infected with MenC/cc11 was identified in a limited area in the northern part of Italy. All cases presented a severe clinical picture, and two of them were fatal. This report is focused on the microbiological and molecular analysis of meningococcal isolates with the aim to reconstruct the chain of transmission. It further presents the vaccination strategy adopted to control the outbreak. The phylogenetic evaluation demonstrated the close genetic proximity between the strain involved in this outbreak and a strain responsible for a larger epidemic that had occurred in 2015 and 2016 in the Tuscany Region. The rapid identification and characterisation of IMD cases and an extensive vaccination campaign contributed to the successful control of this outbreak caused by a hyperinvasive meningococcal strain.

Paradoxes and synergies: optimizing management of a deadly virus in an endangered carnivore.

Pathogen management strategies in wildlife are typically accompanied by an array of uncertainties such as the efficacy of vaccines or potential unintended consequences of interventions. In the context of such uncertainties, models of disease transmission can provide critical insight for optimizing pathogen management, especially for species of conservation concern. The endangered Florida panther experienced an outbreak of feline leukemia virus (FeLV) in 2002-04, and continues to be affected by this deadly virus. Ongoing management efforts aim to mitigate the effects of FeLV on panthers, but with limited information about which strategies may be most effective and efficient.We used a simulation-based approach to determine optimal FeLV management strategies in panthers. We simulated use of proactive FeLV management strategies (i.e., proactive vaccination) and several reactive strategies, including reactive vaccination and test-and-removal. Vaccination strategies accounted for imperfect vaccine-induced immunity, specifically partial immunity in which all vaccinates achieve partial pathogen protection. We compared the effectiveness of these different strategies in mitigating the number of FeLV mortalities and the duration of outbreaks.Results showed that inadequate proactive vaccination can paradoxically increase the number of disease-induced mortalities in FeLV outbreaks. These effects were most likely due to imperfect vaccine immunity causing vaccinates to serve as a semi-susceptible population, thereby allowing outbreaks to persist in circumstances otherwise conducive to fadeout. Combinations of proactive vaccination with reactive test-and-removal or vaccination, however, had a synergistic effect in reducing impacts of FeLV outbreaks, highlighting the importance of using mixed strategies in pathogen management.Synthesis and applications: Management-informed disease simulations are an important tool for identifying unexpected negative consequences and synergies among pathogen management strategies. In particular, we find that imperfect vaccine-induced immunity necessitates further consideration to avoid unintentionally worsening epidemics in some conditions. However, mixing proactive and reactive interventions can improve pathogen control while mitigating uncertainties associated with imperfect interventions.

Agent-based modelling of reactive vaccination of workplaces and schools against COVID-19

With vaccination against COVID-19 stalled in some countries, increasing vaccine accessibility and distribution could help keep transmission under control. Here, we study the impact of reactive vaccination targeting schools and workplaces where cases are detected, with an agent-based model accounting for COVID-19 natural history, vaccine characteristics, demographics, behavioural changes and social distancing. In most scenarios, reactive vaccination leads to a higher reduction in cases compared with non-reactive strategies using the same number of doses. The reactive strategy could however be less effective than a moderate/high pace mass vaccination program if initial vaccination coverage is high or disease incidence is low, because few people would be vaccinated around each case. In case of flare-ups, reactive vaccination could better mitigate spread if it is implemented quickly, is supported by enhanced test-trace-isolate and triggers an increased vaccine uptake. These results provide key information to plan an adaptive vaccination rollout.

The resurgence of yellow fever outbreaks in Nigeria: a 2-year review 2017\u20132019

BackgroundYellow fever outbreaks are documented to have a considerable impact not only on the individuals but on the health system with significant economic implications. Efforts to eliminate yellow fever outbreaks globally through the EYE strategy remains important following outbreaks in Africa, Nigeria included. The outbreaks reported in Nigeria, since 2017 and the response efforts provide an opportunity to document and guide interventions for improving future outbreaks in Nigeria and other countries in Africa.MethodsWe reviewed the available yellow fever surveillance and vaccination response data between September 2017 and September 2019 across the 36 states across Nigeria. We described the epidemiology of the difference outbreaks and the periods for all interventions. We also documented the emergency vaccination responses as well as preventive mass vaccinations implemented towards improving population immunity and limiting epidemic potentials in Nigeria.ResultsA total of 7894 suspected cases with 287 laboratory-confirmed cases were reported in Nigeria between September 2017 and September 2019 with a mean age of 19 years and a case fatality of 2.7% amongst all reported cases. Outbreaks were confirmed in 55 LGAs with most of the outbreaks across four major epicentres in Kwara/Kogi, Edo, Ebonyi and Bauchi states. In response to these outbreaks, eight reactive vaccination campaigns, supported through ICG applications, were implemented. The duration for responding to the outbreaks ranged from 15 to 132 days (average 68 days) and a total of 45,648,243 persons aged < 45 years vaccinated through reactive and preventive mass campaigns between September 2017 and September 2019.ConclusionsNigeria experienced intermediate outbreaks of yellow fever between September 2017 and 2019 with vaccination responses conducted to control these outbreaks. However, there are delays in the timeliness of responses and more efforts required in improving reporting, response times and preparedness to further prevent morbidity and mortality from the yellow fever disease outbreaks. These efforts, including improving routine yellow fever coverage, contribute towards improving population immunity and other activities related to achieving the goals of the EYE strategy.

Meningococcal Disease Outbreaks: A Moving Target and a Case for Routine Preventative Vaccination.

Outbreaks of invasive meningococcal disease (IMD) are unpredictable, can be sudden and have devastating consequences. We conducted a non-systematic review of the literature in PubMed (1997–2020) to assess outbreak response strategies and the impact of vaccine interventions. Since 1997, IMD outbreaks due to serogroups A, B, C, W, Y and X have occurred globally. Reactive emergency mass vaccination campaigns have encompassed single institutions (schools, universities) through to whole sections of the population at regional/national levels (e.g. serogroup B outbreaks in Saguenay–Lac-Saint-Jean region, Canada and New Zealand). Emergency vaccination responses to IMD outbreaks consistently incurred substantial costs (expenditure on vaccine supplies, personnel costs and interruption of other programmes). Impediments included the limited pace of transmission of information to parents/communities/healthcare workers; issues around collection of informed consents; poor vaccine uptake by older adolescents/young adults, often a target age group; issues of reimbursement, particularly in the USA; and difficulties in swift supply of large quantities of vaccines. For serogroup B outbreaks, the need for two doses was a significant issue that contributed substantially to costs, delayed onset of protection and non-compliance with dose 2. Real-world descriptions of outbreak control strategies and the associated challenges systematically show that reactive outbreak management is administratively, logistically and financially costly, and that its impact can be difficult to measure. In view of the unpredictability, fast pace and potential lethality of outbreak-associated IMD, prevention through routine vaccination appears the most effective mitigation tool. Highly effective vaccines covering five of six disease-causing serogroups are available. Preparedness through routine vaccination programmes will enhance the speed and effectiveness of outbreak responses, should they be needed (ready access to vaccines and need for a single booster dose rather than a primary series).Plain Language Summary

Estimating the economic burden of pneumococcal meningitis and pneumonia in northern Ghana in the African meningitis belt post-PCV13 introduction

BackgroundGhana introduced 13-valent pneumococcal conjugate vaccine (PCV13) into the routine infant immunization program in 2012, using a three-dose primary series without a booster. Despite ≥ 88% reported three-dose vaccination coverage since 2013, PCV13-type pneumococcal meningitis outbreaks have occurred. We estimated the ongoing economic burden of PCV13-type pneumococcal meningitis and pneumonia in northern Ghana, an area within the African meningitis belt with seasonal increases of pneumococcal meningitis post-PCV13 introduction, to inform PCV13 vaccination policy. MethodsWe performed a cross-sectional survey among patients with pneumonia or meningitis at three hospitals in northern Ghana to determine patient-level costs (direct medical and nonmedical, indirect patient and caregiver costs) incurred in household, outpatient, and inpatient settings. Pneumonia burden was estimated using 2017–2018 administrative records. Pneumococcal meningitis burden was estimated using 2017–2018 case-based surveillance data. Economic burden was reported in 2019 U.S. dollars ($) from the societal perspective. ResultsFor an area with a total population of 5,068,521, our model estimated 6,441 PCV13-type pneumonia cases and 286 PCV13-type meningitis cases occurred in a typical year post-PCV13. In the base case scenario, the total economic burden was $5,230,035 per year ($777 per case). By age group, cost per PCV13-type pneumonia case was $423 (<5 years), $911 (5–14 years), and $784 (≥15 years); cost per PCV13-type meningitis case was $2,128 (<5 years), $3,247 (5–14 years), and $2,883 (≥15 years). Most (78.0–93.4%) of the total societal cost was due to indirect costs related to deaths from PCV13-type diseases. ConclusionsThe estimated economic burden of PCV13-type disease in northern Ghana remains substantial, especially in older children and adults who were expected to have benefited from indirect effects from infant immunization. Additional interventions such as changes in the infant immunization schedule, reactive vaccination, or catch-up PCV13 vaccination may be needed to control remaining vaccine-type disease.

Etiology and Risk Factors for Meningitis during an Outbreak in Batié Health District, Burkina Faso, January-March 2016

INTRODUCTION: On 16 March 2016, Batié Health District notified the Burkina Faso Min-istry of Health Surveillance unit of 12 suspected cases of meningitis. During the same period, Batié’s neighboring districts in Côte d´Ivoire and Ghana were experiencing a meningitis epi-demic. We investigated to establish the etiology and risk factors for the disease and to recommend prevention and control measures. METHODS: We conducted unmatched case-control study. A case was any person living in Batié with fever (temp. ? 38.5°C) and any of the following: neck stiffness, neurological disor-der, bulging fontanelle, convulsion during January to April 2016 with cerebrospinal fluid (CSF) positive to PCR. Controls were non sick household members, neighbors or friends to the cases. We analyzed the investigation and laboratory records. We included all confirmed cases and two neighborhood controls per case. We used a standard questionnaire to collect data. We analyzed data by Epi info 7 and calculated odds ratio (ORs),adjusted odds ratios (AOR) and 95% confidence interval. We proceeded to univariate, bivariate, multivariate and logistic re-gression analysis. RESULTS: We interviewed 93 participants including 31 meningitis cases and 62 controls. The median age of cases was 8 years old [2 months-55 years] and 6.5 years old [5 months-51 years] for controls. <i>Streptococcus pneumoniae </i>16(51.61%), <i>Neisseria meningitidis W </i>14(45.16%) and <i>Haemophilus influenzae </i>b 1(3.23%) were the identified germs. The independent risk factors identified were travel to meningitis affected areas (Adjusted odd ra-tio(AOR)=12[2.3-60],p=0.0029); >5 persons sharing bedroom (AOR=5.7[1.5-22],p=0.012) and rhino-pharyngitis (AOR=26[1.8-380],p=0.017).CONCLUSION: Streptococcus pneumoniae and Neisseria meningitidis W caused the out-break in Batié. The risk factors were overcrowding, travel to affected areas, and rhino-pharyngitis. We recommended reactive vaccination against Neisseria meningitidis W, limited travel to affected areas and ventilation of rooms.

A reactive vaccination campaign with single dose oral cholera vaccine (OCV) during a cholera outbreak in Cameroon

BackgroundCameroon chose Oral Cholera Vaccine (OCV) mass vaccination campaign in addition to other interventions to respond to outbreaks since 2015. There is still a persistent controversy on the effectiveness of reactive OCV mass vaccination campaign. ObjectiveThis article aimed to share evidence-based observations on the effect of a reactive single-dose OCV mass vaccination campaign on cholera cases in Cameroon. MethodsHealth area centered risk analysis was used to identify nine high risk health areas among four health districts in the |North Region as hotspots. About 537,274 people at risk of cholera transmission one year of age and above including pregnant women were eligible to receive OCV. A total of 537,279 doses of OCV was deployed for vaccination from August 1–5, 2019 through door-to-door strategy for urban health districts, and fixed/ temporary fixed posts strategies for rural health districts. ResultsThe overall vaccination coverage was 99.9%. Vaccine wastage rate was less than 0.5% (0.0011%). Independent monitoring showed vaccination coverage at 97.2%. The 2019 epidemic curve went down after OCV intervention on the contrary to that in the year 2018 at the same period. After OCV intervention, cholera cases dropped from about 10.5 to 9.3 cases per week at the regional level while at the district level, they dropped from 5.3 to 2.1, 2.2 to 1.7, 0.6 to 0 and 1.7 to 1.5 cases per week respectively for Garoua, Garoua II, Tchollire and Pitoa. Though not statistically significant (p = 1.4, α = 0.05), cases per 1000 population seemed to remain unchanged among OCV zones (0.32/1000) and non-OCV zones (0.31/1000) in 2018 while they increased from 0.37 (OCV zones) to 0.53 (non-0CV zones) cases per 1000 population in 2019. ConclusionThere might have been a general trend in the reduction of the number of new cases after a reactive single-dose OCV campaign.

Reactive mass vaccination campaign against cholera in the COVID-19 context in Cameroon: challenges, best practices and lessons learned.

Introductionsince 1971, Cameroon is facing a growing series of cholera epidemics despite all the efforts made by the government to address this huge public health threat. In 2020, in addition to the COVID-19 pandemic, Cameroon recorded a high cholera case fatality rate of 4.3% following epidemics noted in the South, Littoral and South-West regions. The Cameroon Ministry of Public Health, has thus organized a reactive vaccination campaign against cholera to address the high mortality rate in the affected health districts of those regions. The objective of this study was to describe the challenges, best practices and lessons learned drawing from daily experiences from this reactive vaccination campaign against cholera.Methodswe conducted a cross-sectional study drawn from the results of the campaign. We had a target population of 631,109 participants aged 1 year and above resident of the targeted health areas.Resultsthe overall vaccination coverage was 64.4% with a refusal rate ranging from 0-10% according to health districts. Vaccination coverage was the lowest among people aged 20 years and above. The main challenge was difficulty maintaining physical distanciation, the main best practice was the screening of all actors taking part at the vaccination against COVID-19 and we found that emphasizing on thorough population sensitization through quarter heads and social mobilizers and adequately programming the campaign during a good climate season is crucial to achieving good vaccination coverage.Conclusionlessons learned from this study could serve to inform various agencies in the event of planning rapid mass vaccination programs during pandemics.

Measles outbreak investigation in Kambia District, Sierra Leone-2018

Background: Measles, an acute highly infectious viral disease, remains one of the leading causes of childhood morbidity and mortality worldwide. Despite the availability of safe and effective vaccines, measles cases have been reported in Sierra Leone. On 29 October 2018, the Kambia district health management team was notified of a suspected measles outbreak. On 1 November 2019, we investigated the outbreak to confirm the diagnosis, assess the magnitude, identify potential risk factors, and institute control measures. Methods and materials: We defined a suspected case as any person with fever and maculopapular rash in Kambia district from 1st October 2018 and a probable case as any suspected case with epidemiologic link to a laboratory confirmed case. We reviewed medical records, interviewed parents, patients and collected blood samples for measles confirmation. We collected patients’ demographic, clinical and exposure history. We conducted active case search and needs assessment for measles reactive mass vaccination in the community. We conducted social mobilization and risk communication. Results: A total of 91 cases (14 laboratory-confirmed and 77 probable cases) with no deaths reported. The overall Attack Rate (AR) was 24.2/100,000 persons, with the highest AR (119.6/100,000 persons) among the 6–11 months age group. The median age was 24.5 months (range 4–348), and 48 (56%) were females. Four out of seven chiefdoms were affected and Gibnleh-Dixon chiefdom was the most affected (AR = 274.9/100,000). The first four detected cases had travel history to the neighboring Republic of Guinea, where there was a confirmed measles outbreak, and three of the four affected villages are close to the border. The district administrative vaccination coverage was 87%, however, of the total 84 eligible cases, only two had vaccination cards. Conclusion: A measles outbreak was confirmed in Kambia district which shares a border with Guinea. The importation of measles cases in a susceptible community might have contributed to the spread of measles in the affected chiefdoms. A reactive mass vaccination targeting children aged six months to 15 years was conducted and achieved coverage of 100.8%. We recommended strengthening routine immunization through increased outreach vaccination sessions to communities, supplementary vaccination and to strengthen cross border surveillance and response framework.

Emergence of Neisseria meningitidis serogroup X in the 2017/2018 Cerebrospinal Meningitis outbreak, Nigeria

Background: Outbreaks of meningitis occur periodically in Nigeria, with the northern parts mostly affected. Neisseria meningitidis is the commonest cause of meningitis outbreaks; Streptococcus pneumoniae and Haemophilus influenzae causes. Following a large outbreak in 2016/2017, another outbreak occurred in 2017/2018, with Neisseria meningitis C being the cause. This study is aimed at characterizing Neisseria meningitidis strains using genotypic technique (PCR) and bringing to limelight the need for continued surveillance, especially with the emergence of Neisseria meningitidis serogroup X, which like serogroup C, is also capable of causing epidemics. Methods and materials: We conducted active surveillance of suspected meningitis cases that met the WHO case definition in states that reported cases of meningitis between November 2017 and June 2018. CSF was collected from suspected meningitis cases and aliquots sent to the National Reference Laboratory, Abuja from States that reported cases and analysed by culture, Rapid Diagnostic Test (Pastorex®) and Polymerase Chain Reaction for detection of N. meningitidis, S. pneumoniae and H. influenzae. Results: 548 samples were analysed by PCR to detect sodC, lytA and hpd genes. Neisseria meningitidis (n = 236, 43.1.0%; NmC = 182, 33.2%, NmX = 43, 8.0%. others = 11, 2.0%) was the predominant cause of meningitis followed by S. pneumoniae (n = 22, 4.0%) and Haemophilus influenzae (n = 26, 4.7%). Conclusion: This study detected an unusual serogroup of Nm, although outbreaks of meningitis in Nigeria have previously been caused by NmA and NmC. Our data underscores the urgent need for ongoing bio surveillance. The increasing incidence of Neisseria meningitidis X is worrisome, because the reactive and preventive vaccination for meningitis does not cover this serogroup, countries in the African meningitis belt must prepare to face this potential new challenge. Information has been shared with the Nigeria Centre for Disease Control and WHO for further action.

Successive epidemic waves of cholera in South Sudan between 2014 and 2017: a descriptive epidemiological study

SummaryBackgroundBetween 2014 and 2017, successive cholera epidemics occurred in South Sudan within the context of civil war, population displacement, flooding, and drought. We aim to describe the spatiotemporal and molecular features of the three distinct epidemic waves and explore the role of vaccination campaigns, precipitation, and population movement in shaping cholera spread in this complex setting.MethodsIn this descriptive epidemiological study, we analysed cholera linelist data to describe the spatiotemporal progression of the epidemics. We placed whole-genome sequence data from pandemic Vibrio cholerae collected throughout these epidemics into the global phylogenetic context. Using whole-genome sequence data in combination with other molecular attributes, we characterise the relatedness of strains circulating in each wave and the region. We investigated the association of rainfall and the instantaneous basic reproduction number using distributed lag non-linear models, compared county-level attack rates between those with early and late reactive vaccination campaigns, and explored the consistency of the spatial patterns of displacement and suspected cholera case reports.FindingsThe 2014 (6389 cases) and 2015 (1818 cases) cholera epidemics in South Sudan remained spatially limited whereas the 2016–17 epidemic (20 438 cases) spread among settlements along the Nile river. Initial cases of each epidemic were reported in or around Juba soon after the start of the rainy season, but we found no evidence that rainfall modulated transmission during each epidemic. All isolates analysed had similar genotypic and phenotypic characteristics, closely related to sequences from Uganda and Democratic Republic of the Congo. Large-scale population movements between counties of South Sudan with cholera outbreaks were consistent with the spatial distribution of cases. 21 of 26 vaccination campaigns occurred during or after the county-level epidemic peak. Counties vaccinated on or after the peak incidence week had 2·2 times (95% CI 2·1–2·3) higher attack rates than those where vaccination occurred before the peak.InterpretationPandemic V cholerae of the same clonal origin was isolated throughout the study period despite interepidemic periods of no reported cases. Although the complex emergency in South Sudan probably shaped some of the observed spatial and temporal patterns of cases, the full scope of transmission determinants remains unclear. Timely and well targeted use of vaccines can reduce the burden of cholera; however, rapid vaccine deployment in complex emergencies remains challenging.FundingThe Bill & Melinda Gates Foundation.

Yellow fever outbreak investigation in Mgbakwu, Awka North Local Government Area (LGA), Anambra State, Southeast Nigeria - Entomological perspective.

Background:Nigeria has reported cases of Yellow fever (YF) since 2017.Cases have been confirmed in at least 18 states, including the capital, Abuja. The disease is mostly transmitted by mosquitoes of the Aedes genus. We determined the risk of transmission of YF in Dunokofia, Awka-North and Awka-South Local Government Areas.Method:We conducted a baseline study to establish presence of the vectors and risk of the disease transmission in one community each of the three LGAs (Dunokofia, AwkaNorth and Awka-South) of Anambra State. We used major mosquito sampling methods – ovitrapping, larval survey, human landing catch and light trapping – to ascertain the biting and breeding behavior of the vector. We collected samples day and night. We identified adult collections right in the field using standard identification keys, while immature stages were reared to adults for proper identification. Results:A total of 1,014 mosquitoes were collected in the study. Of these,72 (7.1%) were YF non-related vectors while Aedes species (Ae. aegypti, Ae. albopictus, Ae. circumluteolus and Ae. simpsoni complex) accounted for 942 (92.9%). Aedes albopictus, 478 (50.7%) and Aedes aegypti, 461 (49%) were predominant across all locations surveyed. The House Index ranged from 60-80% while the Breteau Index ranged from 75-131, across all sites. No Aedes mosquito was collected indoors.Conclusion:The high larval indices, abundance and diversity of the vectors across the study locations make them high-risk areas for transmission of the disease. This is underscored by the YF outbreak in Awka-North LGA and the large number of primates in the study area. There was Immediate reactive mass vaccination in the affected State. Residual treatment of discarded containers, as well as massive community sensitization and mobilization on larval source reduction, to reduce vector density in the study area were recommended and initiated.

Estimation of Rift Valley fever virus spillover to humans during the Mayotte 2018–2019 epidemic

Rift Valley fever (RVF) is an emerging, zoonotic, arboviral hemorrhagic fever threatening livestock and humans mainly in Africa. RVF is of global concern, having expanded its geographical range over the last decades. The impact of control measures on epidemic dynamics using empirical data has not been assessed. Here, we fitted a mathematical model to seroprevalence livestock and human RVF case data from the 2018-2019 epidemic in Mayotte to estimate viral transmission among livestock, and spillover from livestock to humans through both direct contact and vector-mediated routes. Model simulations were used to assess the impact of vaccination on reducing the epidemic size. The rate of spillover by direct contact was about twice as high as vector transmission. Assuming 30% of the population were farmers, each transmission route contributed to 45% and 55% of the number of human infections, respectively. Reactive vaccination immunizing 20% of the livestock population reduced the number of human cases by 30%. Vaccinating 1 mo later required using 50% more vaccine doses for a similar reduction. Vaccinating only farmers required 10 times as more vaccine doses for a similar reduction in human cases. Finally, with 52.0% (95% credible interval [CrI] [42.9-59.4]) of livestock immune at the end of the epidemic wave, viral reemergence in the next rainy season (2019-2020) is unlikely. Coordinated human and animal health surveillance, and timely livestock vaccination appear to be key to controlling RVF in this setting. We furthermore demonstrate the value of a One Health quantitative approach to surveillance and control of zoonotic infectious diseases.

Evaluation of pneumococcal meningitis clusters in Burkina Faso and implications for potential reactive vaccination

BackgroundTo better understand how to prevent and respond to pneumococcal meningitis outbreaks in the meningitis belt, we retrospectively examined Burkina Faso’s case-based meningitis surveillance data for pneumococcal meningitis clusters and assessed potential usefulness of response strategies. MethodsDemographic and clinical information, and cerebrospinal fluid laboratory results for meningitis cases were collected through nationwide surveillance. Pneumococcal cases were confirmed by culture, polymerase chain reaction (PCR), or latex agglutination; strains were serotyped using PCR. We reviewed data from 2011 to 2017 to identify and describe clusters of ≥ 5 confirmed pneumococcal meningitis cases per week in a single district. We assessed whether identified clusters met the 2016 WHO provisional pneumococcal meningitis outbreak definition: a district with a weekly incidence of >5 suspected meningitis cases/100,000 persons, >60% of confirmed meningitis cases caused by Streptococcus pneumoniae, and >10 confirmed pneumococcal meningitis cases. ResultsTwenty pneumococcal meningitis clusters were identified, with a maximum weekly incidence of 7 cases and a maximum duration of 4 weeks. Most identified clusters (15/20; 75%) occurred before nationwide introduction of 13-valent pneumococcal conjugate vaccine (PCV13) in October 2013. Most cases were due to serotype 1 (74%), 10% were due to PCV13 serotypes besides serotype 1, and 8 clusters had >1 serotype. While 6 identified clusters had a weekly incidence of >5 suspected cases/100,000 and all 20 clusters had >60% of confirmed meningitis cases due to S. pneumoniae, no cluster had >10 confirmed pneumococcal meningitis cases in a single week. ConclusionsFollowing PCV13 introduction, pneumococcal meningitis clusters were rarely detected, and none met the WHO provisional pneumococcal outbreak definition. Due to the limited cluster size and duration, there were no clear instances where reactive vaccination could have been useful. More data are needed to inform potential response strategies.

The reactive vaccination campaign against cholera emergency in camps for internally displaced persons, Borno, Nigeria, 2017: a two-stage cluster survey

IntroductionIn 2017, amidst insecurity and displacements posed by Boko Haram armed insurgency, cholera outbreak started in the Muna Garage camp for Internally Displaced Persons (IDPs) in Borno State, Nigeria. In...

Movement patterns of free-roaming dogs on heterogeneous urban landscapes: Implications for rabies control

In 2015, a case of canine rabies in Arequipa, Peru indicated the re-emergence of rabies virus in the city. Despite mass dog vaccination campaigns across the city and reactive ring vaccination and other control activities around positive cases (e.g. elimination of unowned dogs), the outbreak has spread. Here we explore how the urban landscape of Arequipa affects the movement patterns of free-roaming dogs, the main reservoirs of the rabies virus in the area. We tracked 23 free-roaming dogs using Global Positioning System (GPS) collars. We analyzed the spatio-temporal GPS data using the time- local convex hull method. Dog movement patterns varied across local environments. We found that water channels, an urban feature of Arequipa that are dry most of the year, promote movement. Dogs that used the water channels extensively move on average 7 times further (p = 0.002) and 1.2 times more directionally (p = 0.027) than dogs that do not use the water channels at all. They were also 1.3 times faster on average, but this difference was not statistically significant (p = 0.197). Our findings suggest that water channels can be used by dogs as ‘highways’ to transverse the city and have the potential to spread disease far beyond the radius of control practices. Control efforts should focus on a robust vaccination campaign attuned to the geography of the city, and not limited to small-scale rings surrounding cases.

Field challenges to measles elimination in the Democratic Republic of the Congo

BackgroundDuring a measles epidemic, the Ministry of Public Health (MOH) of the Democratic Republic of the Congo conducted supplementary immunization activities (2016-SIA) from August 28-September 3, 2016 throughout Maniema Province. From October 29-November 4, 2016, Médecins Sans Frontières and the MOH conducted a reactive measles vaccination campaign (2016-RVC) targeting children six months to 14 years old in seven health areas with heavy ongoing transmission despite inclusion in the 2016-SIA, and a post-vaccination survey. We report the measles vaccine coverage (VC) and effectiveness (VE) of the 2016-SIA and VC of the 2016-RVC. MethodsA cross-sectional VC cluster survey stratified by semi-urban/rural health area and age was conducted. A retrospective cohort analysis of measles reported by the parent/guardian allowed calculation of the cumulative measles incidence according to vaccination status after the 2016-SIA for an estimation of crude and adjusted VE. ResultsIn November 2016, 1145 children (6–59 months old) in the semi-urban and 1158 in the rural areas were surveyed. Post-2016-SIA VC (documentation/declaration) was 81.6% (95%CI: 76.5–85.7) in the semi-urban and 91.0% (95%CI: 84.9–94.7) in the rural areas. The reported measles incidence in October among children less than 5 years old was 5.0% for 2016-SIA-vaccinated and 11.2% for 2016-SIA-non-vaccinated in the semi-urban area, and 0.7% for 2016-SIA-vaccinated and 4.0% for 2016-SIA-non-vaccinated in the rural area. Post-2016-SIA VE (adjusted for age, sex) was 53.9% (95%CI: 2.9–78.8) in the semi-urban and 78.7% (95%CI: 0–97.1) in the rural areas. Post 2016-RVC VC (documentation/declaration) was 99.1% (95%CI: 98.2–99.6) in the semi-urban and 98.8% (95%CI: 96.5–99.6) in the rural areas. ConclusionsAlthough our VE estimates could be underestimated due to misclassification of measles status, the VC and VE point estimates of the 2016-SIA in the semi-urban area appear suboptimal, and in combination, could not limit the epidemic. Further research is needed on vaccination strategies adapted to urban contexts.

Quantifying the success of measles vaccination campaigns in the Rohingya refugee camps

In the wake of the Rohingya population's mass migration from Myanmar, one of the world's largest refugee settlements was constructed in Cox's Bazar, Bangladesh to accommodate nearly 900,000 new refugees. Refugee populations are particularly vulnerable to infectious disease outbreaks due to many population and environmental factors. A large measles outbreak, with over 1700 cases, occurred among the Rohingya population between September and November 2017. Here, we estimate key epidemiological parameters and use a dynamic mathematical model of measles transmission to evaluate the effectiveness of the reactive vaccination campaigns in the refugee camps. We also estimate the potential for subsequent outbreaks under different vaccination coverage scenarios. Our modeling results highlight the success of the vaccination campaigns in rapidly curbing transmission and emphasize the public health importance of maintaining high levels of vaccination in this population, where high birth rates and historically low vaccination coverage rates create suitable conditions for future measles outbreaks.