Causal inference concepts applied to three observational studies in the context of vaccine development : from theory to practice

Background Randomized controlled trials are considered the gold standard to evaluate causal associations, whereas assessing causality in observational studies is challenging. Methods We applied Hill's Criteria, counterfactual reasoning, and causal diagrams to evaluate a potentially causal relationship between an exposure and outcome in three published observational studies: a) one burden of disease cohort study to determine the association between type 2 diabetes and herpes zoster, b) one post-authorization safety cohort study to assess the effect of AS04-HPV-16/18 vaccine on the risk of autoimmune diseases, and c) one matched case-control study to evaluate the effectiveness of a rotavirus vaccine in preventing hospitalization for rotavirus gastroenteritis. Results Among the 9 Hill's criteria, 8 (Strength, Consistency, Specificity, Temporality, Plausibility, Coherence, Analogy, Experiment) were considered as met for study c, 3 (Temporality, Plausibility, Coherence) for study a, and 2 (Temporary, Plausibility) for study b. For counterfactual reasoning criteria, exchangeability, the most critical assumption, could not be tested. Using these tools, we concluded that causality was very unlikely in study b, unlikely in study a, and very likely in study c. Directed acyclic graphs provided complementary visual structures that identified confounding bias and helped determine the most accurate design and analysis to assess causality. Conclusions Based on our assessment we found causal Hill's criteria and counterfactual thinking valuable in determining some level of certainty about causality in observational studies. Application of causal inference frameworks should be considered in designing and interpreting observational studies

Exploring the concept of functional vitamin D deficiency in pregnancy: impact of the interaction between 25-hydroxyvitamin D and parathyroid hormone on perinatal outcomes

Background: Associations of vitamin D with perinatal outcomes are inconsistent and few studies have considered the wider calcium metabolic system. Objectives: We aimed to explore functional vitamin D deficiency in pregnancy by investigating associations between vitamin D status, parathyroid hormone (PTH), and perinatal outcomes. Design: SCOPE (Screening for Pregnancy Endpoints) Ireland is a prospective cohort study of low-risk, nulliparous pregnant women. We measured serum 25-hydroxyvitamin D [25(OH)D] and PTH at 15 wk of gestation in 1754 participants. Results: Mean ± SD 25(OH)D was 56.6 ± 25.8 nmol/L (22.7 ± 10.3 ng/mL) and geometric mean (95% CI) PTH was 7.84 pg/mL (7.7, 8.0 pg/mL) [0.86 pmol/L (0.85, 0.88 pmol/L)]. PTH was elevated in 34.3% of women who had 25(OH)D <30 nmol/L and in 13.9% of those with 25(OH)D ≥75 nmol/L. Whereas 17% had 25(OH)D <30 nmol/L, 5.5% had functional vitamin D deficiency, defined as 25(OH)D <30 nmol/L with elevated PTH. Elevated mean arterial pressure (MAP), gestational hypertension, pre-eclampsia, and small-for-gestational-age (SGA) birth were confirmed in 9.2%, 11.9%, 3.8%, and 10.6% of participants, respectively. In fully adjusted regression models, neither low 25(OH)D nor elevated PTH alone increased the risk of any individual outcome. The prevalence of elevated MAP (19.1% compared with 9.7%) and SGA (16.0% compared with 6.7%) were highest (P < 0.05) in those with functional vitamin D deficiency compared with the reference group [25(OH)D ≥75 nmol/L and normal PTH]. The adjusted prevalence ratio (PR) and RR (95% CIs) for elevated MAP and SGA were 1.83 (1.02, 3.27) and 1.53 (0.80, 2.93), respectively. There was no effect of functional vitamin D deficiency on the risk of gestational hypertension (adjusted RR: 1.00; 95% CI: 0.60, 1.67) or pre-eclampsia (adjusted RR: 1.17; 95% CI: 0.32, 4.20). Conclusion: The concept of functional vitamin D deficiency, reflecting calcium metabolic stress, should be considered in studies of vitamin D in pregnancy. The SCOPE pregnancy cohort is registered at http://www.anzctr.org.au as ACTRN12607000551493

A crisis of protection and safe passage: violence experienced by migrants/refugees travelling along the Western Balkan corridor to Northern Europe.

BACKGROUND: Pushed by ongoing conflicts and pulled by the desire for a better life, over one million migrants/refugees transited Balkan countries and arrived in Europe during 2015 and early 2016. To curb this influx, European countries instituted restrictive migration policies often characterized by building of razor-wire border fences and border closures. Among migrants/refugees who received mental health care in Serbia while travelling through Balkan countries to Northern Europe, we assessed the prevalence and patterns of violent events experienced including physical trauma. METHODS: A mixed methods study among migrants/refugees attending mobile mental health clinics run by Médecins sans Frontières (MSF) between July 2015 and June 2016, in Serbia - a main transit hub to European countries. Clinics were conducted according to MSF guidelines by experienced psychologists who were supported by cultural mediators. The main outcome measures were violent events and associated physical trauma. RESULTS: Of 992 migrants/refugees attending MSF mental health clinics, the majority (72%) were from Syria and Afghanistan and included vulnerable groups (14%) such as unaccompanied minors and pregnant women. The most frequent mental health symptoms/signs were anxiety (29%) and adjustment reactions (26%). Of the 992 migrants/refugees, 270 (27%) had experienced violent events during their journey. Signs of physical trauma due to acts of violence were seen in 223(22%) of the 992 individuals, 144 (65%) being perpetrated by State authorities and involving women (11%) and children (13%). Border closures along the Balkan route were associated with a dramatic decrease in registered migrants/refugee arrivals in Serbia. Conversely, among those that made it across the borders, an increasing linear trend in reported violent events was observed at MSF mental health clinics (X2 for linear trend, P <0 · 001). Qualitative evidence corroborated with quantitative findings. CONCLUSIONS: Nearly one-in-three migrants/refugees seen in MSF clinics experienced violent events including physical trauma along their journey. State authorities, including those in European countries were the perpetrators in over half of such events which were associated with border closures. There is "a crisis of protection and safe passage" which needs to change towards one of respect for the principles of international human rights and refugee law

Antenatal vitamin D status is not associated with standard neurodevelopmental assessments at age 5 Years in a well-characterized prospective maternal-infant cohort

Background: Although animal studies show evidence for a role of vitamin D during brain development, data from human studies show conflicting signals. Objective: We aimed to explore associations between maternal and neonatal vitamin D status with childhood neurodevelopmental outcomes. Methods: Comprehensive clinical, demographic, and lifestyle data were collected prospectively in 734 maternal-infant dyads from the Cork BASELINE Birth Cohort Study. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were quantified at 15 weeks of gestation and in umbilical cord sera at birth via a CDC-accredited liquid chromatography-tandem mass spectrometry method. Children were assessed at age 5 y through the use of the Kaufman Brief Intelligence Test (2nd Edition, KBIT-2) and the Child Behaviour Checklist (CBCL). Linear regression was used to explore associations between 25(OH)D and neurodevelopmental outcomes. Results: 25(OH)D concentrations were <30 nmol/L in 15% of maternal and 45% of umbilical cord sera and <50 nmol/L in 42% of mothers and 80% of cords. At age 5 y, the mean ± SD KBIT-2 intelligence quotient (IQ) composite score was 104.6 ± 8.6; scores were 107.2 ± 10.0 in verbal and 99.8 ± 8.8 in nonverbal tasks. Developmental delay (scores <85) was seen in <3% of children across all domains. The mean ± SD CBCL total problem score was 21.3 ± 17.5; scores in the abnormal/clinical range for internal, external, and total problem scales were present in 12%, 4%, and 6% of participants, respectively. KBIT-2 and CBCL subscale scores at 5 y were not different between children exposed to low antenatal vitamin D status, either at 30 or 50 nmol/L 25(OH)D thresholds. Neither maternal nor cord 25(OH)D (per 10 nmol/L) were associated with KBIT-2 IQ composite scores [adjusted β (95% CI): maternal –0.01 (−0.03, 0.02); cord 0.01 (−0.03, 0.04] or CBCL total problem scores [maternal 0.01 (−0.04, 0.05); cord 0.01 (−0.07, 0.09)]. Conclusion: In this well-characterized prospective maternal-infant cohort, we found no evidence that antenatal 25(OH)D concentrations are associated with neurodevelopmental outcomes at 5 y. The BASELINE Study was registered at www.clinicaltrials.gov as NCT01498965; the SCOPE Study was registered at http://www.anzctr.org.au as ACTRN1260700055149

Functional characterization of cytochrome b5 reductase and its electron acceptor cytochrome b5 in Plasmodium falciparum

Malaria is a disease of major public health importance, killing approximately one million people and causing about 250 million cases of fever annually. It mostly affects children under the age of five and pregnant women in many developing countries, making it a prominent issue in international health and maternal and child health. The most aggressive form of malaria is caused by the parasite Plasmodium falciparum which is responsible for 80% of infections and 90% of deaths from malaria, and is most prevalent in sub-Saharan Africa. Public Health interventions include the implementation of prevention programs, health education, and chemotherapy. The latter has experienced multiple problems in the past years whereby resistance of the parasite to the available drugs has emerged, rendering the majority of them ineffective. Furthermore, the high cost of those drugs represents a major obstacle to their dispensation in areas of the world where the affected people are often the less fortunate. The enzyme Cytochrome b5 Reductase (cb5r) and its electron acceptor Cytochrome b5 (cb5) play a role in fatty acid elongation, cholesterol biosynthesis, and cytochrome P450-mediated detoxification of xenobiotics. Therefore, these proteins are suitable as potential novel drug targets for malaria. These two proteins have been thoroughly studied in mammals but have to be characterized in microorganisms such as fungi and parasites, including Plasmodium falciparum. It is important to note that plant cb5r has been identified as a novel herbicidal target. Considering the close phylogenetic relationship between plant cb5r and Plasmodium falciparum cb5r, we conclude that these plant inhibitors may also serve as promising candidates for a new class of antimalarial drugs against the parasite. In this project, we want to obtain the biochemical and enzymatic characterization of cb5r and cb5 in order to establish whether these two proteins represent potential novel drug targets in Plasmodium falciparum malaria. This initial work may lead to the development of novel drugs which will consequently affect the field of public health with respect to drug delivery, drug resistance, and drug chemotherapy

The impact of insecticide-treated bed nets on malaria incidence in Ixcán, Guatemala and the associated identification of spatial clusters of malaria

This project was conducted to assess the efficacy of insecticide-treated bed nets (ITNs) in protecting people against malaria infection in a rural area of Northern Guatemala characterized by low malaria endemicity with unstable and seasonal transmission. While studies from sub-Saharan Africa have indicated that ITNs are highly efficacious, likely due to favorable conditions such as stable malaria transmission and Anopheles gambiae or An. funestus as primary malaria vectors, a number of studies from other areas of the world, including Latin America, have shown either no protective efficacy of ITNs or even an increased risk of infection for individuals using ITNs. For this purpose, a cluster randomized controlled trial was conducted in 2001 in Ixcán, Guatemala to compare the risk of malaria between 13 intervention villages in which all individuals were provided with an ITN and 13 control villages in which no ITNs were provided. The rates of malaria were measured during two cross-sectional pre-intervention surveys and one post-intervention survey. Results showed a significantly higher risk of malaria infection for people living in intervention villages compared to those living in control villages (RR = 1.81, 95% CI 1.11 – 1.92). These results suggest that ITNs failed to provide protection against malaria in this area of Guatemala, although, notably, the rate of malaria for intervention villages was considerably magnified due to uncommonly high malaria rates in only two of the thirteen intervention villages during the post-intervention survey. It is essential to conduct more studies in areas of unstable malaria transmission to have a better understanding of the extent of ITN efficacy and to compare ITNs to other malaria control strategies such as prompt diagnosis and treatment, indoor residual spraying, vector control, or a combination of them. In addition to the ITN efficacy study, a spatial and temporal evaluation of the study area (the same area in which the ITN efficacy study was conducted) was carried out using two statistics, i.e., the local Moran’s I and the Getis-Ord*(d), to determine whether malaria aggregated in the form of clusters (or outliers). This analysis was performed to reveal patterns of malaria distribution in an area of low malaria endemicity since a thorough understanding of the spatial and temporal patterns of malaria distribution is essential for targeted malaria control programs. Clusters of malaria exhibited high spatial and temporal variations, suggesting that surveillance and spatial analysis should be conducted on a regular basis to create targeted malaria control activities. Overall, results from the ITN efficacy study confirm the lower efficacy of ITNs in an area of unstable and seasonal malaria transmission characterized by seemingly unfavorable conditions such as local malaria vectors ( An. albimanus) that tend to feed when humans are not sleeping and the high proportion of Plasmodium vivax malaria that favors relapses. The results of the spatial analysis, which indicate marked spatial and temporal variations in malaria distribution, also seem to be consistent with a context of unstable and seasonal malaria where the location of clusters over a relatively short period of time (approximately 1 year in this study) can vary considerably

Airway pathogens detected in stable and exacerbated COPD in patients in Asia-Pacific

Background The burden of chronic obstructive pulmonary disease (COPD) in the Asia-Pacific region is projected to increase. Data from other regions show bacterial and viral infections can trigger acute exacerbations of COPD (AECOPD). Methods This 1-year prospective epidemiological study (ClinicalTrials.gov identifier: NCT03151395) of patients with moderate to very severe COPD in Hong Kong, the Philippines, South Korea and Taiwan assessed the prevalence in sputum samples (by culture and PCR) of bacterial and viral pathogens during stable COPD and AECOPD. The odds of experiencing an exacerbation was evaluated for pathogen presence, acquisition and apparition. Health-related quality of life (HRQOL) was assessed. Results 197 patients provided 983 sputum samples, with 226 provided during exacerbation episodes. The mean yearly AECOPD incidence rate was 1.27 per patient. The most prevalent bacteria by PCR at exacerbation were Haemophilus influenzae (Hi) and Moraxella catarrhalis (Mcat); Mcat prevalence was higher at exacerbation than at stable state. Virus prevalence was low, other than for human rhinovirus (HRV) (8.1%, stable state; 16.6%, exacerbation). The odds ratio (95% CI) for an exacerbation (versus stable state) was statistically significant for the presence, acquisition and apparition of Hi (2.20, 1.26–3.89; 2.43, 1.11–5.35; 2.32, 1.20–4.46, respectively), Mcat (2.24, 1.30–3.88; 5.47, 2.16–13.86; 3.45, 1.71–6.98, respectively) and HRV (2.12, 1.15–3.91; 2.22, 1.09–4.54; 2.09, 1.11–3.91, respectively). HRQOL deteriorated according to the number of exacerbations experienced. Conclusion In patients with COPD in the Asia-Pacific region, the presence of Hi, Mcat or HRV in sputum samples significantly increased the odds of an exacerbation, providing further evidence of potential roles in triggering AECOPD

Impact of bacterial strain acquisition in the lung of patients with COPD: the AERIS study

BACKGROUND: Bacterial infections are associated with acute exacerbations of chronic obstructive pulmonary disease (AECOPD), but the mechanism is incompletely understood.METHOD: In a COPD observational study (NCT01360398), sputum samples were collected monthly at the stable state and exacerbation. Post-hoc analyses of 1307 non-typeable Haemophilus influenzae (NTHi) isolates from 20 patients and 756 Moraxella catarrhalis isolates from 38 patients in one year of follow-up were conducted by multilocus sequence typing (MLST). All isolates came from cultured sputum samples that were analyzed for bacterial species presence, apparition (infection not detected at the preceding visit), or acquisition (first-time infection), with the first study visit as a baseline. Strain apparition or new strain acquisition was analyzed by MLST. The odds ratio (OR) of experiencing an exacerbation vs. stable state was estimated by conditional logistic regression modelling, stratified by patient.RESULTS: The culture results confirmed a significant association with exacerbation only for NTHi species presence (OR 2.28; 95% confidence interval [CI]: 1.12-4.64) and strain apparition (OR 2.38; 95% CI: 1.08-5.27). For M. catarrhalis, although confidence intervals overlapped, the association with exacerbation for first-time species acquisition (OR 5.99; 2.75-13.02) appeared stronger than species presence (OR 3.67; 2.10-6.40), new strain acquisition (OR 2.94; 1.43-6.04), species apparition (OR 4.18; 2.29-7.63), and strain apparition (OR 2.78; 1.42-5.42). This may suggest that previous M. catarrhalis colonization may modify the risk of exacerbation associated with M. catarrhalis infection.CONCLUSIONS: The results confirm that NTHi and M. catarrhalis infections are associated with AECOPD but suggest different dynamic mechanisms in triggering exacerbations.</p

Coexisting conditions and concomitant medications do not affect venetoclax management and survival in chronic lymphocytic leukemia

The question of which parameters may be informative on venetoclax outcome in chronic lymphocytic leukemia (CLL) is still unclear. Furthermore, the choice to treat with venetoclax can be challenging in patients with baseline characteristics or comorbidities that may potentially favor some specific adverse events