Germany, seeking a path out of lockdown, begins broad random testing for antibodies.

While other nations are still struggling to test for infections, Germany is doing that and more. It is aiming to sample the entire population for antibodies in coming months, hoping to gain valuable insight into how deeply the virus has penetrated the society at large, how deadly it really is, and whether immunity might be developing.

In Munich, residents of 3,000 households chosen at random are being asked to allow monthly blood tests for Covid-19 antibodies for a year. It’s an ambitious study whose central aim is to understand how many people — even those with no symptoms — have already had the virus, a key variable to make decisions about public life in a pandemic.

The Munich research is the largest of several regional studies being rolled out in various corners of the country, which has become a leader among Western nations figuring out how to control the contagion while returning to something resembling normal life.

The government hopes to use the findings to unravel a riddle that will allow Germany to move securely into the next phase of the pandemic: Which of the far-reaching social and economic restrictions that have slowed the virus are most effective and which can be safely lifted?