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

Until 23 June 2022, 539.1 million people had been diagnosed with Covid-19. This number consists only of those who have actually tested themselves and had live virus detected in their bodies and is therefore lower than the actual number of those who have had the disease since March 2020. An article from the Lancet from 2022 estimates that 44% (or 3, 4 billion) have been infected. The gap in registered infected and the number of likely infected is therefore large and this was the background for carrying out the study, many in Norway believed that this gap was also large in 2020/2021. The number of those who have been diagnosed as ill can be used for a lot, but in order to understand the disease and its spread in Norway even better, it would have been nice to know how many people have actually had the virus in their bodies since the pandemic broke out. To find this out, you can test, via a small blood sample, the presence of so-called antibodies. If they are present, you have had the virus in your body at one point or another. If, for example, the total number of confirmed infected people in Norway was 1% and a representative sample of participants in a study shows that 3% have antibodies, we understand that the official number of infected people is greatly underestimated. In this project, we collected blood samples from 27,700 people living in Norway at the end of 2020 and the beginning of 2021, all over the age of 16. The samples showed that 0.9% had antibodies and had the virus in their bodies. The official number of infected people at the same time was 0.8%. In other words, there were very few cases in Norway that were not registered. It shows again that the testing, isolation, infection tracing and quarantine arrangements (TISK) we had in Norway were very effective. It is a very important lesson to take with you for the next time something like this happens.