Following the onset of the ongoing COVID-19 pandemic throughout the world, a large fraction of the global population is or has been under strict measures of physical distancing and quarantine, with many countries being in partial or full lockdown. These measures are imposed in order to reduce the spread of the disease and to lift the pressure on healthcare systems. Estimating the impact of such interventions as well as monitoring the gradual relaxing of these stringent measures is quintessential to understand how resurgence of the COVID-19 epidemic can be controlled for in the future. In this paper we use a stochastic age-structured discrete time compartmental model to describe the transmission of COVID-19 in Belgium. Our model explicitly accounts for age-structure by integrating data on social contacts to (i) assess the impact of the lockdown as implemented on March 13, 2020 on the number of new hospitalizations in Belgium; (ii) conduct a scenario analysis estimating the impact of possible exit strategies on potential future COVID-19 waves. More specifically, the aforementioned model is fitted to hospital admission data, data on the daily number of COVID-19 deaths and serial serological survey data informing the (sero)prevalence of the disease in the population while relying on a Bayesian MCMC approach. Our age-structured stochastic model describes the observed outbreak data well, both in terms of hospitalizations as well as COVID-19 related deaths in the Belgian population. Despite an extensive exploration of various projections for the future course of the epidemic, based on the impact of adherence to measures of physical distancing and a potential increase in contacts as a result of the relaxation of the stringent lockdown measures, a lot of uncertainty remains about the evolution of the epidemic in the next months.

The COVID-19 pandemic caused many governments to impose policies restricting social interactions. A controlled and persistent release of lockdown measures covers many potential strategies and is subject to extensive scenario analyses. Here, we use an individual-based model (STRIDE) to simulate interactions between 11 million inhabitants of Belgium at different levels including extended household settings, i.e., “household bubbles”. The burden of COVID-19 is impacted by both the intensity and frequency of physical contacts, and therefore, household bubbles have the potential to reduce hospital admissions by 90%. In addition, we find that it is crucial to complete contact tracing 4 days after symptom onset. Assumptions on the susceptibility of children affect the impact of school reopening, though we find that business and leisure-related social mixing patterns have more impact on COVID-19 associated disease burden. An optimal deployment of the mitigation policies under study require timely compliance to physical distancing, testing and self-isolation.

Background Partner notification is essential to the comprehensive case management of sexually transmitted infections. Systematic reviews and mathematical modelling can be used to synthesise information about the effects of new interventions to enhance the outcomes of partner notification. Objective To study the effectiveness and cost-effectiveness of traditional and new partner notification technologies for curable sexually transmitted infections (STIs). Design Secondary data analysis of clinical audit data; systematic reviews of randomised controlled trials (MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials) published from 1 January 1966 to 31 August 2012 and of studies of health-related quality of life (HRQL) [MEDLINE, EMBASE, ISI Web of Knowledge, NHS Economic Evaluation Database (NHS EED), Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA)] published from 1 January 1980 to 31 December 2011; static models of clinical effectiveness and cost-effectiveness; and dynamic modelling studies to improve parameter estimation and examine effectiveness. Setting General population and genitourinary medicine clinic attenders. Participants Heterosexual women and men. Interventions Traditional partner notification by patient or provider referral, and new partner notification by expedited partner therapy (EPT) or its UK equivalent, accelerated partner therapy (APT). Main outcome measures Population prevalence; index case reinfection; and partners treated per index case. Results Enhanced partner therapy reduced reinfection in index cases with curable STIs more than simple patient referral [risk ratio (RR) 0.71; 95% confidence interval (CI) 0.56 to 0.89]. There are no randomised trials of APT. The median number of partners treated for chlamydia per index case in UK clinics was 0.60. The number of partners needed to treat to interrupt transmission of chlamydia was lower for casual than for regular partners. In dynamic model simulations, > 10% of partners are chlamydia positive with look-back periods of up to 18 months. In the presence of a chlamydia screening programme that reduces population prevalence, treatment of current partners achieves most of the additional reduction in prevalence attributable to partner notification. Dynamic model simulations show that cotesting and treatment for chlamydia and gonorrhoea reduce the prevalence of both STIs. APT has a limited additional effect on prevalence but reduces the rate of index case reinfection. Published quality-adjusted life-year (QALY) weights were of insufficient quality to be used in a cost-effectiveness study of partner notification in this project. Using an intermediate outcome of cost per infection diagnosed, doubling the efficacy of partner notification from 0.4 to 0.8 partners treated per index case was more cost-effective than increasing chlamydia screening coverage. Conclusions There is evidence to support the improved clinical effectiveness of EPT in reducing index case reinfection. In a general heterosexual population, partner notification identifies new infected cases but the impact on chlamydia prevalence is limited. Partner notification to notify casual partners might have a greater impact than for regular partners in genitourinary clinic populations. Recommendations for future research are (1) to conduct randomised controlled trials using biological outcomes of the effectiveness of APT and of methods to increase testing for human immunodeficiency virus (HIV) and STIs after APT; (2) collection of HRQL data should be a priority to determine QALYs associated with the sequelae of curable STIs; and (3) standardised parameter sets for curable STIs should be developed for mathematical models of STI transmission that are used for policy-making. Funding The National Institute for Health Research Health Technology Assessment programme.

Does the prevalence of adverse maternal and neonatal outcomes vary in women diagnosed with polycystic ovary syndrome (PCOS) according to different definitions? A comparison of different criteria revealed that there is a substantial risk for perinatal complications in PCOS women, regardless of the used definition. Pregnant women with PCOS are susceptible to perinatal complications. At present, there are three main definitions for PCOS. So far, we are aware of only one study, which found that the elevated risk for complications varied widely depending on the different phenotypes and features but only considered a relatively small sample size for some of the phenotypes. Retrospective matched cohort study. Data of primiparous women with PCOS according to ESHRE/ASRM 2003 criteria and healthy controls giving birth to neonates ≥500 g were included. A total of 885 women were analysed: out of 177 women with PCOS, 85 (48.0%) met the National Institutes of Health (NIH) 1990 criteria, another 14 (7.9%) featured the additional phenotypes defined by The Androgen Excess and PCOS Society (AE-PCOS) 2006 criteria, 78 (44.1%) were classified as PCOS exclusively by the ESHRE/ASRM 2003 definition, and 708 represented the control group. The prevalence of adverse maternal (49.4 versus 64.3 versus 60.3%, P = 0.313) and neonatal (27.1 versus 35.7 versus 23.1%, P = 0.615) outcomes did not differ within the three PCOS groups (ESHRE/ASRM, NIH, AE-PCOS, respectively). Compared with healthy controls, the risk for maternal complications was increased in PCOS patients [odds ratio (OR) 2.57; 95% confidence interval (CI) 1.82–3.64; P < 0.001] while there was no difference in neonatal complications (OR 0.83; 95% CI 0.56–1.21; P = 0.343). A limitation of our study is its retrospective design and the relatively small sample size, particularly in the AE-PCOS subgroup. Since women with PCOS have, regardless of the used definition, a high risk of maternal and neonatal complications they should be informed and advised to follow regular checks in units where problems can be detected early to allow specialized care. Marietta Blau Grant (Austrian Agency for International Cooperation in Education and Research; OeAD-GmbH) and mobility scholarship (Medical University of Graz).

To assess the evolving SARS-CoV-2 seroprevalence and seroincidence related to the national lock-down in Belgium, a nationwide seroprevalence study, stratified by age, sex and region using 3000-4000 residual samples was performed during 7 periods between 30 March and 17 October 2020. Residual sera from ambulatory patients were analyzed for IgG antibodies against S1 proteins of SARS-CoV-2 with a semi-quantitative commercial ELISA. Weighted seroprevalence (overall, by age category and sex) and seroincidence during 7 consecutive periods were estimated for the Belgian population while accommodating test-specific sensitivity and specificity. The weighted overall seroprevalence initially increased from 1.8% (95% CrI 1.0-2.6) to 5.3% (95% CrI 4.2-6.4), implying a seroincidence of 3.4% (95% CrI 2.4-4.6) between the 1 ^st and 2 ^nd collection period over a period of 3 weeks during the lockdown period (start lockdown mid March 2020). Thereafter, seroprevalence stabilized, however, significant decreases are observed when comparing the 3 ^rd with the 5 ^th and also with the 6 ^th period resulting in negative seroincidence estimates after lockdown was lifted. We estimated for the last collection period mid October 2020 a weighted overall seroprevalence of 4.2% (95% CrI 3.1-5.2). During lockdown, an initial small but increasing fraction of the Belgian population showed serologically detectable signs of exposure to SARS-CoV-2, which did not further increase when confinement measures eased and full lockdown was lifted.