Effectiveness of BNT162b2 Vaccine Against Omicron-SARS-CoV-2 Subvariants in Children 5-11 Years of Age in Quebec, Canada, January 2022 to January 2023.

BACKGROUND: In premarketing clinical trials conducted before Omicron emergence, BNT162b2 vaccine efficacy against COVID-19 was 90% in children. We conducted postmarketing evaluation of 1- and 2-dose vaccine effectiveness (VE) against Omicron BA.1, BA.2 and BA.4/5 subvariants in 5- to 11-year olds. METHODS: We estimated VE against SARS-CoV-2 infection using a test-negative design. Specimens collected between January 9, 2022, and January 7, 2023, from children 5-11 years old in Quebec, Canada, and tested by nucleic acid amplification test were eligible. We estimated VE by time since last vaccine dose, interval between doses and by period of Omicron subvariant predominance. RESULTS: A total of 48,826 NAATs were included in overall analysis. From 14-55 to 56-385 days postvaccination, 2-dose VE against symptomatic infection decreased from 68% (95% CI, 62-74) to 25% (95% CI, 11-36). Two-dose VE with restriction to specimens collected from acute care hospitals (emergency rooms or wards) did not decline but was stable at ~40%. VE against symptomatic infection remained comparable at any interval between doses but increased with longer interval among children tested in acute care settings, from 18% (95% CI, -17 to 44) with 21- to 55-day interval to 69% (95% CI, 43-86) with ≥84-day interval. Two-dose VE against symptomatic infection dropped from 70% (95% CI, 63-76) during BA.1, to 32% (95% CI, 13-47) with BA.2 and to nonprotective during BA.4/5 dominance. CONCLUSIONS: In children 5-11 years of age, VE against symptomatic infection was stable at any interval between doses but decreased with time since the last dose and against more divergent omicron subvariants.

Transmission of Antimicrobial Resistant Yersinia pestis During a Pneumonic Plague Outbreak.

BACKGROUND: Pneumonic plague (PP), caused by Yersinia pestis, is the most feared clinical form of plague due to its rapid lethality and potential to cause outbreaks. PP outbreaks are now rare due to antimicrobial therapy. METHODS: A PP outbreak in Madagascar involving transmission of a Y. pestis strain resistant to streptomycin, the current recommended first-line treatment in Madagascar, was retrospectively characterized using epidemiology, clinical diagnostics, molecular characterization, and animal studies. RESULTS: The outbreak occurred in February 2013 in the Faratsiho district of Madagascar and involved 22 cases, including 3 untreated fatalities. The 19 other cases participated in funeral practices for the fatal cases and fully recovered after combination antimicrobial therapy: intramuscular streptomycin followed by oral co-trimoxazole. The Y. pestis strain that circulated during this outbreak is resistant to streptomycin resulting from a spontaneous point mutation in the 30S ribosomal protein S12 (rpsL) gene. This same mutation causes streptomycin resistance in 2 unrelated Y. pestis strains, one isolated from a fatal PP case in a different region of Madagascar in 1987 and another isolated from a fatal PP case in China in 1996, documenting this mutation has occurred independently at least 3 times in Y. pestis. Laboratory experiments revealed this mutation has no detectable impact on fitness or virulence, and revertants to wild-type are rare in other species containing it, suggesting Y. pestis strains containing it could persist in the environment. CONCLUSIONS: Unique antimicrobial resistant (AMR) strains of Y. pestis continue to arise in Madagascar and can be transmitted during PP outbreaks.

How could an African swine fever outbreak evolve in an enzootic context? The case of Imerintsiatosika, Madagascar in 2015.

African swine fever (ASF) is a haemorrhagic contagious pig disease generally causing high mortality. ASF is enzootic in Madagascar with outbreaks reported each year. An ASF outbreak occurred in May 2015 in the municipality of Imerintsiatosika in Madagascar. We investigated the outbreak to describe it and to identify risk factors in order to propose control measures, and to document evidence of an ASF outbreak in an enzootic country. We took biological samples from very sick and dying pigs, sold by the farmer to the butcher, for PCR analysis. An active search for all possible farm-cases was carried out. A definition of suspected farm-case was established and we implemented a descriptive survey and a retrospective cohort study. Laboratory results confirmed ASF virus infection. Suspected farm-cases represented 81 farms out of 922. Out of 3081 pigs of infected farms, 44% (95% CI: 42-46%) were sick, of which 47% were sold or slaughtered. Case fatality was 60% (95% CI: 56-63%) while 21% (95% CI: 19-24%) of the diseased pigs recovered. The outbreak duration was nine months and half of the infected farms' pig population remained after the outbreak. Compared to the exotic breed, local pigs had twice the risk of infection. It is the first detailed report of an ASF outbreak in an enzootic situation. The disease still has a large impact with 50% animals lost. However, the case fatality is lower than expected that suggests the possibility of resistance and subclinical cases. Proximity to road and increased number of farms are risk factors so biosecurity measures are needed. Further studies are needed to understand why pigs of local breed are more affected. Finally, an acceptable alternative to the sale of sick animals should be found as this currently is the breeders' means to reducing economic loss.

Evaluation of the reinforced integrated disease surveillance and response strategy using short message service data transmission in two southern regions of Madagascar, 2014-15.

BACKGROUND: The Integrated Disease Surveillance and Response (IDSR) strategy was introduced in Madagascar in 2007. Information was collected by Healthcare structures (HS) on paper forms and transferred to the central level by post or email. Completeness of data reporting was around 20% in 2009-10. From 2011, in two southern regions data were transmitted through short messages service using one telephone provider. We evaluated the system in 2014-15 to determine its performance before changing or expanding it. METHODS: We randomly selected 80 HS and interviewed their representatives face-to-face (42) or by telephone (38). We evaluated knowledge of surveillance activities and selected case definitions, number of SMS with erroneous or missing information among the last ten transferred SMS, proportion of weekly reports received in the last 4 weeks and of the last four health alerts notified within 48 h, as well as mobile phone network coverage. RESULTS: Sixty-four percent of 80 interviewed HS representatives didn't know their terms of reference, 83% were familiar with the malaria case definition and 32% with that of dengue. Ninety percent (37/41) of visited HS had five or more errors and 47% had missing data in the last ten SMS they transferred. The average time needed for weekly IDSR data compilation was 24 min in the Southern and 47 in the South-eastern region. Of 320 expected SMS 232 (73%) were received, 136 (43%) of them in time. Out of 38 alerts detected, four were notified on time. Nine percent (7/80) of HS had no telephone network with the current provider. CONCLUSIONS: SMS transfer has improved IDSR data completeness, but timeliness and data quality remain a problem. Healthcare staff needs training on guidelines and case definitions. From 2016, data are collected and managed electronically to reduce errors and improve the system's performance.

Four years into the Indian ocean field epidemiology training programme.

INTRODUCTION: Following the 2005-6 chikungunya outbreak, a project to strengthen regional Public Health preparedness in the Indian Ocean was implemented. It includes the Comoros, Madagascar, Mauritius, Reunion (France) and Seychelles. A Field Epidemiology Training Programme (FETP-OI) was started in 2011 to develop a pool of well-trained intervention epidemiologists. METHODS: The FETP-OI consists of two years of supervised, learning-by-doing, on-the-job training at national sites involved in disease surveillance and response. It includes work placements at the Madagascar Pasteur Institute and the French regional epidemiology unit in Reunion and up to three training courses per year. Training objectives include epidemiological surveillance, outbreak investigations, research studies, scientific communication and transfer of competencies. RESULTS: In four years, two cohorts of in total 15 fellows originating from four countries followed the FETP-OI. They led 42 surveillance projects (71% routine management, 14% evaluations, 12% setup, 3% other) and investigated 36 outbreak alerts, 58% of them in Madagascar; most investigations (72%) concerned foodborne pathogens, plague or malaria. Fellows performed 18 studies (44% descriptive analyses, 22% disease risk factors, and 34% on other subjects), and presented results during regional and international conferences through 26 oral and 15 poster presentations. Four articles were published in regional Public Health bulletins and several scientific manuscripts are in process. CONCLUSION: The FETP-OI has created a regional force of intervention consisting of field epidemiologists and trained supervisors using the same technical language and epidemiological methods. The third cohort is now ongoing. Technically and financially sustainable FETP-OI projects help addressing public health priorities of the Indian Ocean.

Multiple causes of an unexpected malaria outbreak in a high-transmission area in Madagascar.

BACKGROUND: The malaria burden in Madagascar dropped down last decade, largely due to scale-up of control measures. Nevertheless, a significant rise of malaria cases occurred in 2011-2012 in two regions of the rainy South-Eastern Madagascar, where malaria is considered as mesoendemic and the population is supposed to be protected by its acquired immunity against Plasmodium. A multidisciplinary investigation was conducted in order to identify the causes of the outbreak. METHODS: In March 2012, a cross-sectional study was conducted in 20 randomly selected clusters, involving the rapid diagnostic testing of all ≥6 month-old members of households and a questionnaire about socio-demographic data and exposure to malaria control interventions. Changes in environmental conditions were evaluated by qualitative interview of local authorities, climatic conditions were evaluated by remote-sensing, and stock outs of malaria supplies in health facilities were evaluated by quantitative means. Two long-lasting insecticidal nets (LLINs) were sampled in each cluster in order to evaluate their condition and the remanence of their insecticidal activity. The entomological investigation also encompassed the collection Anopheles vectors in two sites, and the measure of their sensitivity to deltamethrin. RESULTS: The cross-sectional survey included 1615 members of 440 households. The mean Plasmodium infection rate was 25.6 % and the mean bed net use on the day before survey was 71.1 %. The prevalence of Plasmodium infections was higher in 6-14 year-old children (odds ratio (OR) 7.73 [95 % CI 3.58-16.68]), in rural areas (OR 6.25 [4.46-8.76]), in poorest socio-economic tercile (OR 1.54 [1.13-2.08]), and it was lower in individuals sleeping regularly under the bed net (OR 0.51 [0.32-0.82]). Stock outs of anti-malarial drugs in the last 6 months have been reported in two third of health facilities. Rainfalls were increased as compared with the three previous rainy seasons. Vectors collected were sensitive to pyrethroids. Two years after distribution, nearly all LLINs collected showed a loss of physical integrity and insecticide activity, CONCLUSIONS: Increased rainfall, decreasing use and reduced insecticide activity of long-lasting insecticide-treated nets, and drug shortages may have been responsible for, or contributed to, the outbreak observed in South-Eastern Madagascar in 2011-2012. Control interventions for malaria elimination must be sustained at the risk of triggering harmful epidemics, even in zones of high transmission.