Background incidence rates of health outcomes in populations at risk for Lyme disease using US administrative claims data.

BACKGROUND: Background incidence rates (IRs) of health outcomes in Lyme disease endemic regions are useful to contextualize events reported during Lyme disease vaccine clinical trials or post-marketing. The objective of this study was to estimate and compare IRs of health outcomes in Lyme disease endemic versus non-endemic regions in the US during pre-COVID and COVID era timeframes. METHODS: IQVIA PharMetrics® Plus commercial claims database was used to estimate IRs of 64 outcomes relevant to vaccine safety monitoring in the US during January 1, 2017-December 31, 2019 and January 1, 2020-December 31, 2021. Analyses included all individuals aged ≥ 2 years with ≥ 1 year of continuous enrollment. Outcomes were defined by International Classification of Diseases Clinical Modification, 10th Revision (ICD-10-CM) diagnosis codes. IRs and 95 % confidence intervals (CIs) were calculated for each outcome and compared between endemic vs. non-endemic regions, and pre-COVID vs. COVID era using IR ratios (IRR). RESULTS: The study population included 8.7 million (M) in endemic and 27.8 M in non-endemic regions. Mean age and sex were similar in endemic and non-endemic regions. In both study periods, the IRs were statistically higher in endemic regions for anaphylaxis, meningoencephalitis, myocarditis/pericarditis, and rash (including erythema migrans) as compared with non-endemic regions. Conversely, significantly lower IRs were observed in endemic regions for acute kidney injury, disseminated intravascular coagulation, heart failure, myelitis, myopathies, and systemic lupus erythematosus in both study periods. Most outcomes were statistically less frequent during the COVID-era. CONCLUSION: This study identified potential differences between Lyme endemic and non-endemic regions of the US in background IRs of health conditions during pre-COVID and COVID era timeframes to inform Lyme disease vaccine safety monitoring. These regional and temporal differences in background IRs should be considered when contextualizing possible safety signals in clinical trials and post-marketing of a vaccine targeted at Lyme disease prevention.

Detecting Rickettsia parkeri infection from eschar swab specimens.

The typical clinical presentation of several spotted fever group Rickettsia infections includes eschars. Clinical diagnosis of the condition is usually made by analysis of blood samples. We describe a more sensitive, noninvasive means of obtaining a sample for diagnosis by using an eschar swab specimen from patients infected with Rickettsia parkeri.

Hepatitis B virus coinfection negatively impacts HIV outcomes in HIV seroconverters.

BACKGROUND: Understanding the impact of hepatitis B virus (HBV) in human immunodeficiency virus (HIV) coinfection has been limited by heterogeneity of HIV disease. We evaluated HBV coinfection and HIV-related disease progression in a cohort of HIV seroconverters. METHODS: Participants with HIV diagnosis seroconversion window of ≤ 3 years and serologically confirmed HBV infection (HB) status were classified at baseline into 4 HB groups. The risk of clinical AIDS/death in HIV seroconverters was calculated by HB status. RESULTS: Of 2352 HIV seroconverters, 474 (20%) had resolved HB, 82 (3%) had isolated total antibody to hepatitis B core antigen (HBcAb), and 64 (3%) had chronic HB. Unadjusted rates (95% confidence intervals [CIs]) of clinical AIDS/death for the HB-negative, resolved HB, isolated HBcAb, and chronic HB groups were 2.43 (2.15-2.71); 3.27 (2.71-3.84); 3.75 (2.25-5.25); and 5.41 (3.41-7.42), respectively. The multivariable risk of clinical AIDS/death was significantly higher in the chronic HB group compared to the HB-negative group (hazard ratio [HR], 1.80; 95% CI, 1.20-2.69); while the HRs were increased but nonsignificant for those with resolved HB (HR, 1.17; 95% CI, .94-1.46) and isolated HBcAb (HR, 1.14; 95% CI, .75-1.75). CONCLUSIONS: HBV coinfection has a significant impact on HIV outcomes. The hazard for an AIDS or death event is almost double for those with chronic HB compared, with HIV-monoinfected persons.

Safety and immunogenicity of a primary series and booster dose of the meningococcal serogroup B-factor H binding protein vaccine (MenB-FHbp) in healthy children aged 1-9 years: two phase 2 randomised, controlled, observer-blinded studies.

BACKGROUND: The meningococcal serogroup B-factor H binding protein vaccine (MenB-FHbp) is licensed for use in children aged 10 years or older for protection against invasive serogroup B meningococcal disease. Because young children are at increased risk of invasive meningococcal disease, MenB-FHbp clinical data in this population are needed. METHODS: We conducted two phase 2 randomised, controlled, observer-blinded studies including healthy toddlers (age 12-23 months) across 26 Australian, Czech, Finnish, and Polish centres, and older children (age 2-9 years) across 14 Finnish and Polish centres. Exclusion criteria included previous vaccinations against serogroup B meningococcus or hepatitis A virus (HAV), and chronic antibiotic use. Toddlers were randomly allocated (2:1) via an interactive response technology system to receive either 60 µg or 120 µg MenB-FHbp or HAV vaccine and saline (control). Older children were randomly allocated (3:1) to receive 120 µg MenB-FHbp or control, with stratification by age group (2-3 years and 4-9 years). All vaccinations were administered as three doses (0, 2, and 6 months, with only saline given at 2 months in the control group). Toddlers who received 120 µg MenB-FHbp could receive a 120 µg booster dose 24 months after the end of the primary series. The percentages of participants with serum bactericidal activity using human complement (hSBA) titres at or above the lower limit of quantification (LLOQ; all greater than the 1:4 correlate of protection) against four test strains of serogroup B meningococcus 1 month after the third dose (primary immunogenicity endpoint) were measured in the evaluable immunogenicity populations (participants who received the vaccine as randomised, had available and determinate hSBA results, and had no major protocol violations). Not all participants were tested against all strains because of serum sample volume constraints. The frequencies of reactogenicity and adverse events after each dose were recorded in the safety population (all participants who received at least one dose and had safety data available). These studies are registered with ClinicalTrials.gov (NCT02534935 and NCT02531698) and are completed. FINDINGS: Between Aug 31, 2015, and Aug 22, 2016, for the toddler study and between Aug 27, 2015, and March 7, 2016, for the older children study, we enrolled and randomly allocated 396 toddlers (60 µg MenB-FHbp group n=44; 120 µg MenB-FHbp group n=220; control group n=132) and 400 older children (120 µg MenB-FHbp group n=294; control group n=106). 1 month after the third dose, the proportions of participants with hSBA titres at or above the LLOQ ranged across test strains from 85·0% (95% CI 62·1-96·8; 17 of 20 participants) to 100·0% (82·4-100·0; 19 of 19) in toddlers receiving 60 µg MenB-FHbp, and from 71·6% (61·4-80·4; 68 of 95) to 100·0% (96·2-100·0; 95 of 95) in toddlers receiving 120 µg MenB-FHbp, and from 79·1% (71·2-85·6; 106 of 134) to 100·0% (97·4-100·0; 139 of 139) in children aged 2-9 years receiving 120 µg MenB-FHbp. hSBA titres peaked at 1 month after the third primary dose of MenB-FHbp and then declined over time. 24 months after the third dose in the toddler study, the proportions with hSBA titres at or above the LLOQ ranged from 0·0% (0·0-17·6; 0 of 19 participants) to 41·2% (18·4-67·1; seven of 17) in those who received 60 µg MenB-FHbp and from 3·7% (0·8-10·4; three of 81) to 22·8% (14·1-33·6; 18 of 79) in those who received 120 µg MenB-FHbp. 1 month after the booster dose in toddlers, the proportions with hSBA titres at or above the LLOQ were higher than at 1 month after the primary series. MenB-FHbp reactogenicity was mostly transient and of mild to moderate severity. Adverse event frequency was similar between the MenB-FHbp and control groups and less frequent following MenB-FHbp booster than following primary doses. Two participants from the toddler study (both from the 120 µg MenB-FHbp group) and four from the older children study (three from the 120 µg MenB-FHbp group and one from the control group) were withdrawn from the study because of adverse events. INTERPRETATION: MenB-FHbp was well tolerated and induced protective immune responses in a high proportion of participants. These findings support a favourable MenB-FHbp immunogenicity and reactogenicity profile in young children, a population at increased risk of adverse invasive meningococcal disease outcomes. FUNDING: Pfizer.

A phase 3 study to assess the immunogenicity, safety, and tolerability of MenB-FHbp administered as a 2-dose schedule in adolescents and young adults.

BACKGROUND: The MenB-FHbp vaccine is licensed to prevent meningococcal serogroup B disease on either a 2-dose (0, 6 months) or 3-dose (0, 1-2, 6 months) series. This phase 3 study further assessed the immunogenicity and safety of the 2-dose MenB-FHbp schedule. METHODS: Subjects 10-25 years of age received MenB-FHbp (months 0, 6) and the quadrivalent meningococcal conjugate vaccine MenACWY-CRM (month 0). Primary immunogenicity endpoints included percentages of subjects achieving ≥ 4-fold increases from baseline in serum bactericidal antibody using human complement (hSBA) titers for 4 diverse, vaccine-heterologous primary serogroup B test strains and titers ≥ lower limit of quantitation (LLOQ; 1:8 or 1:16) for all 4 primary strains combined (composite response) after dose 2; a titer ≥ 1:4 is the accepted correlate of protection. Percentages of participants with hSBA titers ≥ LLOQ for 10 additional vaccine-heterologous strains were also assessed; positive predictive values of primary strain responses for secondary strain responses were determined. Safety was assessed. RESULTS: Overall, 1057 subjects received dose 1 and 946 received dose 2 of MenB-FHbp. Percentages of participants achieving ≥ 4-fold increases in hSBA titers against each primary strain after dose 2 ranged from 67.4% to 95.0% and the composite response was 74.3%. Primary strain responses were highly predictive of secondary strain responses. Most reactogenicity events were mild-to-moderate in severity and did not lead to withdrawal from the study. Adverse events (AEs) considered by the investigator to be related to vaccination occurred in 4.2% (44/1057) of subjects, and there were no serious AEs or newly diagnosed chronic medical conditions considered related to vaccination. CONCLUSIONS: MenB-FHbp administered at 0, 6 months was well tolerated and induced protective bactericidal antibody responses against diverse serogroup B strains. Findings provide further support for the continued use of MenB-FHbp on a 2-dose schedule in this population.

Safety data from the MenB-FHbp clinical development program in healthy individuals aged 10 years and older.

BACKGROUND: The MenB-FHbp vaccine (Trumenba®) is licensed in various countries for the prevention of meningococcal serogroup B disease in individuals ≥ 10 years of age. The clinical development program included 11 completed trials where, in each trial, MenB-FHbp had an acceptable safety profile after a primary vaccination series was administered to individuals 10-65 years of age. However, the detection of potential rare events was limited because of individual clinical trial size. The current safety analysis evaluates pooled reactogenicity and other adverse events (AEs) reported in these trials to identify new safety signals not detectable in individual trials. METHODS: Eleven trials contributed safety data, of which 10 recorded local and systemic reactogenicity events; 8 of the trials were controlled, and reactogenicity data were pooled for 7 of these 8 trials. Additional AE evaluations included immediate AEs (IAEs), medically attended AEs (MAEs), serious AEs (SAEs), newly diagnosed chronic medical conditions (NDCMCs), and autoimmune or neuroinflammatory conditions. RESULTS: Local and systemic reactions were more frequent in the MenB-FHbp group (n = 15,294) compared with controls (n = 5509), although most reactions were transient and mild to moderate in severity. Frequencies of IAEs, SAEs, MAEs, NDCMCs, and autoimmune or neuroinflammatory conditions were similar between the MenB-FHbp and control groups. CONCLUSIONS: MenB-FHbp demonstrated a favorable safety and tolerability profile in the clinical development program of > 15,000 vaccine recipients ≥ 10 years of age. No new safety signals were identified in the pooled analysis compared with data from the individual trials. Continued postmarketing safety surveillance is important for the identification of rare events. Clinicaltrials.gov: NCT01299480; NCT000808028; NCT00879814; NCT00780806; NCT01352845; NCT01352793; NCT01461993; NCT01323270; NCT01830855; NCT01461980; NCT01768117.

Multiple genetic backgrounds of the amplified Plasmodium falciparum multidrug resistance (pfmdr1) gene and selective sweep of 184F mutation in Cambodia.

BACKGROUND: The emergence of artesunate-mefloquine (AS+MQ)-resistant Plasmodium falciparum in the Thailand-Cambodia region is a major concern for malaria control. Studies indicate that copy number increase and key alleles in the pfmdr1 gene are associated with AS+MQ resistance. In the present study, we investigated evidence for a selective sweep around pfmdr1 because of the spread of adaptive mutation and/or multiple copies of this gene in the P. falciparum population in Cambodia. METHODS: We characterized 13 microsatellite loci flanking (+/-99 kb) pfmdr1 in 93 single-clone P. falciparum infections, of which 31 had multiple copies and 62 had a single copy of the pfmdr1 gene. RESULTS: Genetic analysis revealed no difference in the mean (+/- standard deviation) expected heterozygosity (H(e)) at loci around single (0.75+/-0.03) and multiple (0.76+/-0.04) copies of pfmdr1. Evidence of genetic hitchhiking with the selective sweep of certain haplotypes was seen around mutant (184F) pfmdr1 allele, irrespective of the copy number. There was an overall reduction of 28% in mean H(e) (+/-SD) around mutant allele (0.56+/-0.05), compared with wild-type allele (0.84+/-0.02). Significant linkage disequilibrium was also observed between the loci flanking mutant pfmdr1 allele. CONCLUSION: The 184F mutant allele is under selection, whereas amplification of pfmdr1 gene in this population occurs on multiple genetic backgrounds.

Persistence of hSBA titers elicited by the meningococcal serogroup B vaccine menB-FHbp for up to 4 years after a 2- or 3-dose primary series and immunogenicity, safety, and tolerability of a booster dose through 26 months.

BACKGROUND: To demonstrate extended protection against meningococcal serogroup B (MenB) disease after MenB-FHbp (bivalent rLP2086) vaccination, this study evaluated immunopersistence through 26 months following MenB-FHbp boosting after 2 or 3 primary doses in adolescents. STUDY DESIGN: This phase 3, open-label study was an extension of 3 phase 2 studies with participants aged 11-18 years randomized to receive primary MenB-FHbp vaccination following 1 of 5 dosing schedules or control. A booster dose was administered 48 months after the primary series. Immunopersistence through 48 months after the last primary dose (persistence stage) and 26 months postbooster (booster stage) was determined by serum bactericidal assays using human complement (hSBAs) against 4 vaccine-heterologous test strains. Safety evaluations included adverse events (AEs) and local and systemic reactions. RESULTS: Overall, 698 and 304 subjects enrolled in the persistence and booster stages, respectively. hSBA titers declined in all groups during 12 months postprimary vaccination, then remained stable through 48 months. One month postbooster, 93.4-100.0% of subjects achieved hSBA titers ≥ lower limit of quantitation against each test strain; percentages at 12 and 26 months postbooster were higher than at similar time points following primary vaccination. Primary and booster MenB-FHbp vaccinations were well tolerated, with ≤ 12.5% of subjects reporting AEs during each stage. The most common local (reported by 84.4-93.8% of subjects) and systemic (68.8-76.6%) reactions to the booster were injection site pain and fatigue and headache, respectively; ≤ 3.7% of subjects reported severe systemic events. CONCLUSION: Protective hSBA titers initially declined but were retained by many subjects for 4 years irrespective of primary MenB-FHbp vaccination schedule. Boosting at 48 months after primary vaccination was safe, well tolerated, and induced immune responses indicative of immunological memory that persisted through 26 months. Booster vaccination during late adolescence may prolong protection against MenB disease.

Active case detection, treatment of falciparum malaria with combined chloroquine and sulphadoxine/pyrimethamine and vivax malaria with chloroquine and molecular markers of anti-malarial resistance in the Republic of Vanuatu.

BACKGROUND: Chloroquine-resistant Plasmodium falciparum was first described in the Republic of Vanuatu in the early 1980s. In 1991, the Vanuatu Ministry of Health instituted new treatment guidelines for uncomplicated P. falciparum infection consisting of chloroquine/sulphadoxine-pyrimethamine combination therapy. Chloroquine remains the recommended treatment for Plasmodium vivax. METHODS: In 2005, cross-sectional blood surveys at 45 sites on Malo Island were conducted and 4,060 adults and children screened for malaria. Of those screened, 203 volunteer study subjects without malaria at the time of screening were followed for 13 weeks to observe peak seasonal incidence of infection. Another 54 subjects with malaria were followed over a 28-day period to determine efficacy of anti-malarial therapy; chloroquine alone for P. vivax and chloroquine/sulphadoxine-pyrimethamine for P. falciparum infections. RESULTS: The overall prevalence of parasitaemia by mass blood screening was 6%, equally divided between P. falciparum and P. vivax. Twenty percent and 23% of participants with patent P. vivax and P. falciparum parasitaemia, respectively, were febrile at the time of screening. In the incidence study cohort, after 2,303 person-weeks of follow-up, the incidence density of malaria was 1.3 cases per person-year with P. vivax predominating. Among individuals participating in the clinical trial, the 28-day chloroquine P. vivax cure rate was 100%. The 28-day chloroquine/sulphadoxine-pyrimethamine P. falciparum cure rate was 97%. The single treatment failure, confirmed by merozoite surface protein-2 genotyping, was classified as a day 28 late parasitological treatment failure. All P. falciparum isolates carried the Thr-76 pfcrt mutant allele and the double Asn-108 + Arg-59 dhfr mutant alleles. Dhps mutant alleles were not detected in the study sample. CONCLUSION: Peak seasonal malaria prevalence on Malo Island reached hypoendemic levels during the study observation period. The only in vivo malaria drug efficacy trial thus far published from the Republic of Vanuatu showed chloroquine/sulphadoxine-pyrimethamine combination therapy for P. falciparum and chloroquine alone for P. vivax to be highly efficacious. Although the chloroquine-resistant pfcrt allele was present in all P. falciparum isolates, mutant alleles in the dhfr and dhps genes do not yet occur to the extent required to confer sulphadoxine-pyrimethamine resistance in this population.

Molecular surveillance for multidrug-resistant Plasmodium falciparum, Cambodia.

We conducted surveillance for multidrug-resistant Plasmodium falciparum in Cambodia during 2004-2006 by assessing molecular changes in pfmdr1. The high prevalence of isolates with multiple pfmdr1 copies found in western Cambodia near the Thai border, where artesunate-mefloquine therapy failures occur, contrasts with isolates from eastern Cambodia, where this combination therapy remains highly effective.

Discordant patterns of genetic variation at two chloroquine resistance loci in worldwide populations of the malaria parasite Plasmodium falciparum.

Mutations in the chloroquine resistance (CQR) transporter gene of Plasmodium falciparum (Pfcrt; chromosome 7) play a key role in CQR, while mutations in the multidrug resistance gene (Pfmdr1; chromosome 5) play a significant role in the parasite's resistance to a variety of antimalarials and also modulate CQR. To compare patterns of genetic variation at Pfcrt and Pfmdr1 loci, we investigated 460 blood samples from P. falciparum-infected patients from four Asian, three African, and three South American countries, analyzing microsatellite (MS) loci flanking Pfcrt (five loci [approximately 40 kb]) and Pfmdr1 (either two loci [approximately 5 kb] or four loci [approximately 10 kb]). CQR Pfmdr1 allele-associated MS haplotypes showed considerably higher genetic diversity and higher levels of subdivision than CQR Pfcrt allele-associated MS haplotypes in both Asian and African parasite populations. However, both Pfcrt and Pfmdr1 MS haplotypes showed similar levels of low diversity in South American parasite populations. Median-joining network analyses showed that the Pfcrt MS haplotypes correlated well with geography and CQR Pfcrt alleles, whereas there was no distinct Pfmdr1 MS haplotype that correlated with geography and/or CQR Pfmdr1 alleles. Furthermore, multiple independent origins of CQR Pfmdr1 alleles in Asia and Africa were inferred. These results suggest that variation at Pfcrt and Pfmdr1 loci in both Asian and African parasite populations is generated and/or maintained via substantially different mechanisms. Since Pfmdr1 mutations may be associated with resistance to artemisinin combination therapies that are replacing CQ, particularly in Africa, it is important to determine if, and how, the genetic characteristics of this locus change over time.

Pfmdr1 and in vivo resistance to artesunate-mefloquine in falciparum malaria on the Cambodian-Thai border.

Artemisinin combination therapies (ACTs) have recently been adopted as first-line therapy for Plasmodium falciparum infections in most malaria-endemic countries. In this study, we estimated the association between artesunate-mefloquine therapy failure and genetic changes in the putative transporter, pfmdr1. Blood samples were acquired from 80 patients enrolled in an 2004 in vivo efficacy study in Pailin, Cambodia, and genotyped for pfmdr1 copy number and haplotype. Having parasites with three or more copies of pfmdr1 before treatment was strongly associated with recrudescence (hazard ratio [HR] = 8.30; 95% CI: 2.60-26.43). This relationship was maintained when controlling for initial parasite density and hematocrit (HR = 7.91; 95% CI: 2.38-26.29). Artesunate-mefloquine treatment selected for increased pfmdr1 copy number, because isolates from recurrent episodes had higher copy numbers than the paired enrollment samples (Wilcoxon rank test, P = 0.040). pfmdr1 copy number should be evaluated further as a surveillance tool for artesunate-mefloquine resistance in Cambodia.

Relapsing vivax malaria after 6 months of daily atovaquone/proguanil in Afghanistan: the case for expanded use of primaquine as a causal prophylactic.

A 22-year-old soldier presented with vivax malaria after extended travel in Afghanistan. Compliant with atovaquone/proguanil in country, he discontinued prophylaxis immediately upon departure. This case raises important issues regarding prophylactic choice and compliance during travel to Plasmodium vivax endemic locations and primaquine's registration status for prophylaxis and use by practitioners.

Plasmodium vivax-associated acute respiratory distress syndrome after extended travel in Afghanistan.

A 21-year-old soldier developed anorexia, vomiting, diarrhea and fever 10 days after returning to the United States from an 8-month deployment in Afghanistan. His symptoms persisted over the next 5 days until he presented in respiratory failure with a partial pressure oxygen: concentration of inspired oxygen (PaO(2):FiO(2)) ratio of 63, requiring urgent intubation and ventilator support. Chest roentgenogram revealed diffuse bilateral alveolar opacities consistent with acute respiratory distress syndrome. Although sputum and blood cultures did not reveal a causative agent, Giemsa-stained blood smears were positive for Plasmodium vivax alone, which was later confirmed by small subunit ribosomal RNA polymerase chain reaction amplification. After a tenuous course marked by splenic rupture and prolonged requirement for ventilator support, the patient ultimately recovered. Although generally considered benign, this and other recent reports of vivax malaria-associated lung injury emphasize the need for persistent pursuit of the diagnosis in febrile travelers returning from vivax endemic locations as well as aggressive monitoring for and management of life-threatening complications.

Safety and immunogenicity of a recombinant Staphylococcus aureus α-toxoid and a recombinant Panton-Valentine leukocidin subunit, in healthy adults.

We conducted a randomized, double-blind, placebo-controlled dose-escalation study in healthy adults to evaluate the safety and immunogenicity of recombinant Staphylococcus aureus candidate vaccine antigens, recombinant α-toxoid (rAT) and a sub-unit of Panton-Valentine leukocidin (rLukS-PV). 176 subjects were enrolled and randomized within 1 of 11 treatment cohorts: monovalent rAT or rLukS-PV dosages of 10, 25, 50, and 100 µg; bivalent rAT:rLukS dosages of 10:10, 25:25, and 50:50 µg; and alum or saline placebo. All subjects were assessed at Days 0, 7, 14, 28, and 84. Subjects in the 50:50 µg bivalent cohort received a second injection on Day 84 and were assessed on Days 98 and 112. Incidence and severity of reactogenicity and adverse events (AEs) were compared. Geometric mean serum concentrations (GMC) and neutralizing activity of anti-rAT and anti-rLukS-PV IgG were assessed. Reactogenicity incidence was significantly higher in vaccine than placebo recipients (77% versus 55%, respectively; p = 0.006). However, 77% of reactogenicity events were mild and 19% were moderate in severity. The AE incidence and severity were similar between the cohorts. All monovalent and bivalent rAT dosages resulted in a significant increase in the anti-rAT IgG and anti- rLukS-PV GMCs between day 0 and 28 compared with placebo, and persisted through Day 84. Exploratory subgroup analyses suggested a higher GMC and neutralizing antibody titers for the 50 µg monovalent or bivalent rAT and rLukS-PV dose as compared to the other doses. No booster effect was observed after administration of the second dose. We conclude that the rAT and rLukS-PV vaccine formulations were well-tolerated and had a favorable immunogenicity profile, producing antibody with neutralizing activity through day 84. There was no benefit observed with a booster dose of the vaccine.

Mefloquine is highly efficacious against chloroquine-resistant Plasmodium vivax malaria and Plasmodium falciparum malaria in Papua, Indonesia.

BACKGROUND: During the period of 1996-1999, we prospectively monitored 243 Javanese adults and children after arriving in Papua, Indonesia, and microscopically documented each new case of malaria by active surveillance. METHODS: In a randomized, open-label, comparative malaria treatment trial, 72 adults and 50 children received chloroquine for each incident case of malaria, and 74 adults and 47 children received mefloquine. RESULTS: Among 975 primary treatment courses, the cumulative 28-day curative efficacies were 26% and 82% for chloroquine against Plasmodium falciparum malaria and Plasmodium vivax malaria, respectively. Mefloquine cure rates were far superior (96% against P. falciparum malaria and 99.6% against P. vivax malaria). CONCLUSIONS: Mefloquine is a useful alternative treatment for P. vivax malaria and P. falciparum malaria in areas such as Papua, where chloroquine is still recommended as the first-line therapeutic agent.

Rapid onset of transmission-reducing antibodies in javanese migrants exposed to malaria in papua, indonesia.

Transmission of Plasmodium falciparum malaria is initiated by sexual stages in the mosquito. Anti-Pfs48/45 and anti-Pfs230 sexual stage antibodies that are ingested together with parasites can reduce parasite development and subsequently malaria transmission. Acquisition of sexual stage immunity was studied in a cohort of 102 non-immune Javanese individuals migrating to hyperendemic Papua Indonesia. Seroprevalence of antibodies against Pfs48/45 and Pfs230 and functional transmission-reducing activity (TRA) were measured upon arrival and at 6, 12, and 24 months. Asexual parasitemia and gametocytemia were assessed every two weeks. The TRA and seroreactivity increased with the number of P. falciparum infections. The longitudinally sustained association between TRA and antibodies against Pfs48/45 (odds ratio [OR] = 3.74, 95% confidence interval [CI] = 1.51-9.29) and Pfs230 (OR = 3.72, 95% CI = 1.36-10.17) suggests that functional transmission reducing immunity is acquired after limited exposure to infection.

Reader technique as a source of variability in determining malaria parasite density by microscopy.

BACKGROUND: Accurate identification and quantification of malaria parasites are critical for measuring clinical trial outcomes. Positive and negative diagnosis is usually sufficient for the assessment of therapeutic outcome, but vaccine or prophylactic drug trials require measuring density of infection as a primary endpoint. Microscopy is the most established and widely-used technique for quantifying parasite densities in the blood. METHODS: Results obtained by 24-27 expert malaria microscopists, who had independently read 895 slides from 35 donors, were analysed to understand how reader technique contributes to discrepancy in measurements of parasite density over a wide range of densities. RESULTS: Among these 35 donations, standard deviations ranged from 30% to 250% of the mean parasite density and the percent discrepancy was inversely correlated with the mean parasite density. The number of white blood cells indexed and whether parasites were counted in the thick film or thin film were shown to significantly contribute to discrepancy amongst microscopists. CONCLUSION: Errors in microscopy measurements are not widely appreciated or addressed but have serious consequences for efficacy trials, including possibly abandoning promising vaccine candidates.

Combined chloroquine, sulfadoxine/pyrimethamine and primaquine against Plasmodium falciparum in Central Java, Indonesia.

BACKGROUND: Chloroquine (CQ) or sulfadoxine-pyrimethamine (SP) monotherapy for Plasmodium falciparum often leads to therapeutic failure in Indonesia. Combining CQ with other drugs, like SP, may provide an affordable, available and effective option where artemisinin-combined therapies (ACT) are not licensed or are unavailable. METHODS: This study compared CQ (n = 29 subjects) versus CQ + SP (with or without primaquine; n = 88) for clinical and parasitological cure of uncomplicated falciparum malaria in the Menoreh Hills region of southern Central Java, Indonesia. Gametocyte clearance rates were measured with (n = 56 subjects) and without (n = 61) a single 45 mg dose of primaquine (PQ). RESULTS: After 28 days, 58% of subjects receiving CQ had cleared parasitaemia and remained aparasitaemic, compared to 94% receiving CQ combined with SP (p < 0.001). Msp-2 genotyping permitted reinfection-adjusted cure rates for CQ and CQ combined with SP, 70% and 99%, respectively (p = 0.0006). CONCLUSION: Primaquine exerted no apparent affect on cure of asexual stage parasitaemia, but clearly accelerated clearance of gametocytes. CQ combined with SP was safe and well-tolerated with superior efficacy over CQ for P. falciparum parasitaemia in this study.

Production and validation of durable, high quality standardized malaria microscopy slides for teaching, testing and quality assurance during an era of declining diagnostic proficiency.

BACKGROUND: Sets of Giemsa-stained, blood smear slides with systematically verified composite diagnoses would contribute substantially to development of externally validated quality assurance systems for the microscopic diagnosis of malaria. METHODS: whole blood from Plasmodium-positive donors in Cambodia and Indonesia and individuals with no history of risk for malaria was collected. Using standard operating procedures, technicians prepared Giemsa-stained thick and thin smears from each donor. One slide from each of the first 35 donations was distributed to each of 28 individuals acknowledged by reputation as having expertise in the microscopic diagnosis of malaria. These reference readers recorded presence or absence of Plasmodium species and parasite density. A composite diagnosis for each donation was determined based on microscopic findings and species-specific small subunit ribosomal RNA (ssrRNA) DNA polymerase chain reaction (PCR) amplification. RESULTS: More than 12,000 slides were generated from 124 donations. Reference readers correctly identified presence of parasites on 85% of slides with densities <100 parasites/microl, which improved to 100% for densities >350 parasites/microl. Percentages of agreement with composite diagnoses were highest for Plasmodium falciparum (99%), followed by Plasmodium vivax (86%). CONCLUSION: Herein, a standardized method for producing large numbers of consistently high quality, durable Giemsa-stained blood smears and validating composite diagnoses for the purpose of creating a malaria slide repository in support of initiatives to improve training and competency assessment amidst a background of variability in diagnosis is described.