The impact of wildtype SARS-CoV-2 on fatigue and quality of life: prevalence of post COVID-19 condition in a Dutch population-based serosurveillance cohort. (preprint)

Background: Our aim was to assess the relationship between (time since) wild-type SARS-CoV-2 infection and health-related quality of life (HRQoL) and fatigue as endpoints linked to Post COVID-19 condition (PCC). Methods: Participants [≥]15 years were selected from the February 2021 round of the population-based PIENTER Corona study. We investigated the association between (time since) SARS-COV-2 infection and health outcomes: HRQoL (health utility (SF-6D); physical health and mental health (both SF-12)) and fatigue (CIS-fatigue) using multivariable logistic regression analyses adjusted for age, sex, educational level, number of comorbidities, COVID-19 vaccination status, and the intensity of restrictions. For each outcome, multivariable logistic regression models were fitted at cut-off points selected based on the cumulative distribution of those uninfected. Results: Results shown correspond to the cut-off point related to the worst off 15% of each outcome. Significant differences between those uninfected (n=4,614) and cases infected [≤]4 months ago (n=368) were observed for health utility (OR [95%CI]: 1.6 [1.2-2.2]), physical health (OR [95%CI]: 1.7 [1.3-2.3]) and fatigue (OR [95%CI]: 1.6 [1.2-2.0]), but not for mental health. There were no significant differences between uninfected and cases infected >4 months ago (n=345) for all outcomes. Conclusions: In a Dutch population-based cohort of seroconverted individuals, those infected with wild-type SARS-CoV-2 [≤]4 months ago more often reported poor health utility and physical health and were more often severely fatigued compared to those uninfected (at the 15% cut-off). HRQoL and fatigue remained below the detection limit for those infected >4 months ago, suggesting a relatively low prevalence of PCC.

Nationwide SARS-CoV-2 Seroprevalence Trends in the Netherlands in the Variant of Concern Era, 2021-2022: an Ongoing Prospective Cohort Study (preprint)

BackgroundRepeated population-based SARS-CoV-2 serosurveillance is key in complementing other surveillance tools. AimAssessing trends in infection- and/or vaccine-induced immunity, including breakthrough infections, among (sub)groups and regions in the Dutch population during the Variant of Concern (VOC)-era whilst varying levels of stringency, to evaluate population immunity dynamics and inform future pandemic response planning. MethodsIn this prospective population-based cohort, randomly-selected participants (n=9,985) aged 1-92 years (recruited since early-2020) donated home-collected fingerstick blood samples at six timepoints in 2021-2022, covering waves dominated by Alpha, Delta, and Omicron (BA.1, BA.2, BA.5). IgG antibody assessments against Spike-S1 and Nucleoprotein were combined with vaccination- and testing data to estimate infection-induced (inf) and total (infection- and vaccination-induced) seroprevalence. ResultsIn 2021, nationwide inf-seroprevalence rose modestly from 12% since Alpha to 26% amidst Delta, while total seroprevalence increased rapidly to nearly 90%, particularly fast in vulnerable groups (i.e., elderly and those with comorbidities). Highest infection rates were noticeable in adolescents and young adults, low/middle educated elderly, non-Western, contact professions (other than healthcare), and low-vaccination coverage regions. In 2022, following Omicron emergence, inf-seroprevalence elevated sharply to 62% and further to 86%, with frequent breakthrough infections and reduction of seroprevalence dissimilarities between most groups. Whereas >90% of <60-year-olds had been infected, 30% of vaccinated vulnerable individuals had not acquired hybrid immunity. ConclusionAlthough total SARS-CoV-2 seroprevalence had increased rapidly, infection rates were unequally distributed within the Dutch population. Ongoing tailored vaccination efforts and (sero-)monitoring of vulnerable groups remain important given their lowest rate of hybrid immunity and highest susceptibility to severe disease.

Dynamics of non-household contacts during the COVID-19 pandemic in 2020 and 2021 in the Netherlands (preprint)

The COVID-19 pandemic was in 2020 and 2021 for a large part mitigated by reducing contacts in the general population. To monitor how these contacts changed over the course of the pandemic in the Netherlands, a longitudinal survey was conducted where participants reported on their at-risk contacts every two weeks, as part of the European CoMix survey. The survey included 1659 participants from April to August 2020 and 2514 participants from December 2020 to September 2021. We categorized the number of unique contacted persons excluding household members, reported per participant per day into six activity levels, defined as 0, 1, 2, 3-4, 5-9 and 10 or more reported contacts. After correcting for age, vaccination status, risk status for severe outcome of infection, and frequency of participation, activity levels increased over time, coinciding with relaxation of COVID-19 control measures.

Associations between measures of social distancing and SARS-CoV-2 seropositivity: a nationwide population-based study in the Netherlands (preprint)

ABSTRACT This large nationwide population-based seroepidemiological study provides evidence on the effectiveness of physical distancing (>1.5m) and indoor group size reductions on SARS-CoV-2 infection. Additionally, young adults seem to play a significant role in viral spread, opposed to children up until the primary school age with whom close contact is permitted.