Monitoring the population seroprevalence of SARS-CoV-2 infection in Norway to model and predict the current and future epidemics (Map-SARS)

To June 23 2022, 539.1 million people worldwide had been diagnosed with coronavirus disease (Covid-19). However, as these figures are only based on the number detected cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), they are too low. An article from the Lancet (2022) estimates that 44% (or 3.4 billion) people have been infected. This inherent underestimation limits our understanding of the spread of Covid-19 and makes it difficult to develop effective public health strategies. To better understand how many persons have been exposed to the virus, we can look for past disease in blood samples by detection of so-called antibodies. If for example, the detected cases add up to 1% of the Norwegian population and a representative sample from the Norwegian population show antibodies in 3%, we know that there is a large underestimation of the true number of cases in Norway. In this study we collected blood samples from 27 700 Norwegians from November 2020 - January 2021, all above the age of 16. The investigation showed that 0.9% of Norwegians had antibodies and had thus been exposed to the disease. The official proportion of reported cases at the time was 0.8%, indicating that only a very few cases had gone undetected in Norway by January 2021. This shows that the Norwegian strategy related to testing, isolation, infection tracing and quarantine was very effective up to this point at least. It is important to know that when faced with a similar disease in the future, it is possible to detain and slow it down until we know what we are dealing with.

The dataset did provide accurate information on the spread of SARS-CoV-2 amidst the pandemic, just before the first vaccines were administered. The results are published and easily accessible for the public and decision makers. The dataset does, however, contain much more information, including personal information from the participants that can be used for other epidemiological investigations. In addition, we have linked our participants with the official reporting system for infectious diseases (MSIS) to see how many of those with known past infection were missed by the antibody test. We are currently working with a publication that will increase the accuracy of mathematical modelling for estimations of the real number of infected people during a pandemic and the timing of infections in relation to detection of antibodies. Our findings thus far can be used to confirm that the Norwegian strategy related to testing, isolation, infection tracing and quarantine did, in fact, work as intended and managed to slow down and detain the pandemic until we knew what we were dealing with. We did not implement an open-source dashboard. Our data were too limited in time and the seroprevalence so low that coincidence, randomness and rapidly changing restrictions, more than anything else, dictated the spread of the disease. Instead we will use our questionnaires to ascertain which demographic and behavioural characteristics increased or decreased) the risk of infection. The study demonstrated that mass sampling of blood through the use of micro samples without the involvement (or added stress) of the medical community is feasible amidst a pandemic. Lessons learned from this activity have been used actively in global health initiatives in the republic of Georgia, where we are currently setting up a surveillance system involving micro sampling in kids. The micro sampling methods used in the "Monitoring the population seroprevalence of SARS-CoV-2 infection in Norway to model and predict the current and future epidemics" project are being improved so that we are able to sample a known volume of blood, thus allowing relative quantification of virtually any substance present, for example environmental contaminants. If successful, this will virtually eliminate the need for extraction of larger volumes of venous blood in children in the future.

The current COVID-19 pandemic is an emergency with difficult challenges. Most cases have mild symptoms and transmissions occur pre-symptomatically or even asymptomatically. Furthermore, there are large differences in mortality rates between countries. Limited testing and epidemiological uncertainties lead to possible underestimation of the scope of the epidemic. Data are needed to estimate the true prevalence of the disease and tools to assess changes and predictions of the epidemic dynamics. The goals of this project are to assess the seroprevalence the Sars-Cov-2 infection in the Norwegian population at multiple time points, to accurately model the epidemic dynamics and establish a system for continuous assessment of changes in overall immunity in the population. The seroprevalence will be assessed by collecting blood samples in a random sample of 10 000 Norwegians above the age of 16, that will be analysed for the presence of SARS-CoV-2 antibodies. The participants will be asked to donate a blood sample through their Home Doctor Network (Praksisnett). Additionally, the participants will complete a questionnaire with personal information, including living/working conditions and travels. The participants will report symptoms on a weekly basis through the NIPH platform hosted by Helsenorge. The national seroprevalence will be assessed in the fall and early 2021 to assess changes after the summer and the flu season. Additional blood samples may be collected, depending on necessity and availability of funding. Questionnaires and transportation databases will allow machine- and complex network modeling to improve understanding of the evolution of the epidemic. Comparative data analysis will be carried out in collaboration with our international partners (UK and Italy. The project will be part of a national effort and an open source dashboard will be implemented to make data and results available.