collection to running the tests to privacy-protected reporting, and to get the swabs and reagents ready to begin large-scale testing. On Thursday 12 March 2020, the company opened its website to book appointments for testing and within hours 12,000 people had signed up. Testing began the following morning, free of charge. The deCODE effort scaled up quickly to a capacity of over 1000 samples per day. From the beginning of population screening, fewer than 1% of those taking part were found to be infected, indicating that the health authorities' containment strategy was working. From mid-March to the end of May 2020, the company conducted an average of 600 tests a day, complementing the health authorities' 250 tests per day at the National-University Hospital. Those testing positive in deCODE's screening were similarly isolated and their contacts traced and asked to quarantine themselves. In total, by the beginning of June more than 60,000 tests had been conducted in Iceland, equivalent to 18 percent of the population. Powered by this combined testing strategy and tracing and isolation follow up, the number of infections in Iceland peaked in the first week of April and dropped steeply off by the end of the month. By mid-May, there were only a handful of active infections in the country, although deCODE and the health authorities continued to conduct as many as 200 tests per day thereafter to try to detect any fresh outbreaks. In tandem with its screening work, deCODE used its genetics capabilities to sequence the virus from hundreds of infected individuals, and to draw a kind of genealogy of the different clades of the virus in the country. This showed how during the early weeks of the pandemic the virus had entered the country with people infected in different countries and then spread within Iceland. In April 2020, with colleagues from the Directorate of Health and the national hospital, the company published in the New England Journal of Medicine a paper detailing what the spread of COVID-19 looks like across a population, and how a robust policy of testing, tracing and isolation could effectively contain it. In May, the company began work to develop and carry out antibody testing in the population, and early results showed that around one percent of the general population that had not been diagnosed with infection carried antibodies for the virus. This meant on the one hand that the virus