Percorrer por autor "Hens, Niel"
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- Assessing the role of children in the COVID-19 pandemic in Belgium using perturbation analysisPublication . Angeli, Leonardo; Caetano, Constantino Pereira; Franco, Nicolas; Coletti, Pietro; Faes, Christel; Molenberghs, Geert; Beutels, Philippe; Abrams, Steven; Willem, Lander; Hens, NielUnderstanding the evolving role of different age groups in virus transmission is essential for effective pandemic management. We investigated SARS-CoV-2 transmission in Belgium from November 2020 to February 2022, focusing on age-specific patterns. Using a next generation matrix approach integrating social contact data and simulating population susceptibility evolution, we performed a longitudinal perturbation analysis of the effective reproduction number to unravel age-specific transmission dynamics. From November to December 2020, adults in the [18, 60) age group were the main transmission drivers, while children contributed marginally. This pattern shifted between January and March 2021, when in-person education resumed, and the Alpha variant emerged: children aged under 12 years old were crucial in transmission. Stringent social distancing measures in March 2021 helped diminish the noticeable contribution of the [18, 30) age group. By June 2021, as the Delta variant became the predominant strain, adults aged [18, 40) years emerged as main contributors to transmission, with a resurgence in children’s contribution during September-October 2021. This study highlights the effectiveness of our methodology in identifying age-specific transmission patterns.
- Different transmission patterns in the early stages of the influenza A(H1N1)v pandemic: a comparative analysis of 12 European countriesPublication . Flasche, Stefan; Hens, Niel; Boëlle, Pierre-Yves; Mossong, Joël; van Ballegooijen, W. Marijn; Nunes, Baltazar; Rizzo, Caterina; Popovici, Florin; Santa-Olalla, Patricia; Hrubá, Frantiska; Parmakova, Kremena; Baguelin, Marc; van Hoek, Albert Jan; Desenclos, Jean-Claude; Bernillon, Pascale; Cámara, Amparro Larrauri; Wallinga, Jacco; Asikainen, Tommi; White, Peter J.; Edmunds, W. JohnFollowing the emergence of a novel strain of influenza A(H1N1) in Mexico and the United States in April 2009, its epidemiology in Europe during the summer was limited to sporadic and localised outbreaks. Only the United Kingdom experienced widespread transmission declining with school holidays in late July. Using statistical modelling where applicable we explored the following causes that could explain this surprising difference in transmission dynamics: extinction by chance, differences in the susceptibility profile, age distribution of the imported cases, differences in contact patterns, mitigation strategies, school holidays and weather patterns. No single factor was able to explain the differences sufficiently. Hence an additive mixed model was used to model the country-specific weekly estimates of the effective reproductive number using the extinction probability, school holidays and weather patterns as explanatory variables. The average extinction probability, its trend and the trend in absolute humidity were found to be significantly negatively correlated with the effective reproduction number - although they could only explain about 3% of the variability in the model. By comparing the initial epidemiology of influenza A (H1N1) across different European countries, our analysis was able to uncover a possible role for the timing of importations (extinction probability), mixing patterns and the absolute humidity as underlying factors. However, much uncertainty remains. With better information on the role of these epidemiological factors, the control of influenza could be improved.
- Pregnancy during COVID-19: social contact patterns and vaccine coverage of pregnant women from CoMix in 19 European countriesPublication . Wong, Kerry L.M.; Gimma, Amy; Paixao, Enny; Paolotti, Daniela; Karch, André; Jäger, Veronika; Baruch, Joaquin; Melillo, Tanya; Hudeckova, Henrieta; Rosińska-Bukowska, Magdalena; Niedźwiedzka-Stadnik, Marta; Fischer, Krista; Vorobjov, Sigrid; Sõnajalg, Hanna; Althaus, Christian; Low, Nicola; Reichmuth, Martina L.; Auranen, Kari; Nurhonen, Markku; Petrović, Goranka; Makaric, Zvjezdana Lovric; Namorado, Sónia; Caetano, Constantino; Santos, Ana João; Röst, Gergely; Oroszi, Beatrix; Karsai, Márton; Fafangel, Mario; Klepac, Petra; Kranjec, Natalija; Vilaplana, Cristina; Casabona-Barbarà, Jordi; FAES, Christel; Beutels, Philippe; Hens, Niel; Jarvis, Christopher; Edmunds, JohnBackground: Evidence and advice for pregnant women evolved during the COVID-19 pandemic. We studied social contact behaviour and vaccine uptake in pregnant women between March 2020 and September 2021 in 19 European countries. Methods: In each country, repeated online survey data were collected from a panel of nationally-representative participants. We calculated the adjusted mean number of contacts reported with an individual-level generalized additive mixed model, modelled using the negative binomial distribution and a log link function. Mean proportion of people in isolation or quarantine, and vaccination coverage by pregnancy status and gender were calculated using a clustered bootstrap. Findings: We recorded 4,129 observations from 1,041 pregnant women, and 115,359 observations from 29,860 non-pregnant individuals aged 18-49. Pregnant women made slightly fewer contacts (3.6, 95%CI = 3.5-3.7) than non-pregnant women (4.0, 95%CI = 3.9-4.0), driven by fewer work contacts but marginally more contacts in non-essential social settings. Approximately 15-20% pregnant and 5% of non-pregnant individuals reported to be in isolation and quarantine for large parts of the study period. COVID-19 vaccine coverage was higher in pregnant women than in non-pregnant women between January and April 2021. Since May 2021, vaccination in non-pregnant women began to increase and surpassed that in pregnant women. Interpretation: Limited social contact to avoid pathogen exposure during the COVID-19 pandemic has been a challenge to many, especially women going through pregnancy. More recognition of maternal social support desire is needed in the ongoing pandemic. As COVID-19 vaccination continues to remain an important pillar of outbreak response, strategies to promote correct information can provide reassurance and facilitate informed pregnancy vaccine decisions in this vulnerable group.
- Social contact patterns during the COVID-19 pandemic in 21 European countries - evidence from a two-year studyPublication . Wong, Kerry L.M.; Gimma, Amy; Coletti, Pietro; Paolotti, Daniela; Tizzani, Michele; Cattuto, Ciro; Schmidt, Andrea; Gredinger, Gerald; Stumpfl, Sophie; Baruch, Joaquin; Melillo, Tanya; Hudeckova, Henrieta; Zibolenova, Jana; Chladna, Zuzana; Rosinska, Magdalena; Niedzwiedzka-Stadnik, Marta; Fischer, Krista; Vorobjov, Sigrid; Sõnajalg, Hanna; Althaus, Christian; Low, Nicola; Reichmuth, Martina; Auranen, Kari; Nurhonen, Markku; Petrović, Goranka; Makaric, Zvjezdana Lovric; Namorado, Sónia; Caetano, Constantino; Santos, Ana João; Röst, Gergely; Oroszi, Beatrix; Karsai, Márton; Fafangel, Mario; Klepac, Petra; Kranjec, Natalija; Vilaplana, Cristina; Casabona, Jordi; Faes, Christel; Beutels, Philippe; Hens, Niel; Jaeger, Veronika K.; Karch, Andre; Johnson, Helen; Jarvis, Christopher I.Background: Most countries have enacted some restrictions to reduce social contacts to slow down disease transmission during the COVID-19 pandemic. For nearly two years, individuals likely also adopted new behaviours to avoid pathogen exposure based on personal circumstances. We aimed to understand the way in which different factors affect social contacts - a critical step to improving future pandemic responses. Methods: The analysis was based on repeated cross-sectional contact survey data collected in a standardized international study from 21 European countries between March 2020 and March 2022. We calculated the mean daily contacts reported using a clustered bootstrap by country and by settings (at home, at work, or in other settings). Where data were available, contact rates during the study period were compared with rates recorded prior to the pandemic. We fitted censored individual-level generalized additive mixed models to examine the effects of various factors on the number of social contacts. Results: The survey recorded 463,336 observations from 96,456 participants. In all countries where comparison data were available, contact rates over the previous two years were substantially lower than those seen prior to the pandemic (approximately from over 10 to < 5), predominantly due to fewer contacts outside the home. Government restrictions imposed immediate effect on contacts, and these effects lingered after the restrictions were lifted. Across countries, the relationships between national policy, individual perceptions, or personal circumstances determining contacts varied. Conclusions: Our study, coordinated at the regional level, provides important insights into the understanding of the factors associated with social contacts to support future infectious disease outbreak responses.