Dutch authorities report 3% of 10,000 samples of donated blood tested positive for coronavirus antibodies. The days on which samples were collected isn’t reported, but worst case, 3% of the population had developed some immunity as of April 16, when the Netherlands’ per capita mortality was 183 deaths per million. This suggests if the entire population had been infected and received the same quality of health care, there would be 183 / 3% = 6,100 deaths per million. So a 49-year-old (the median age of COVID-19 deaths) faces approximately the same risk as 59-year-old men and 64-year-old women in Canada face from everyday (non-COVID-19) risks.
Estimates suggest that herd immunity is achieved when 50% – 80% of a population is immune. This means the Dutch, who appear to be further along than most countries, aren’t even a tenth of the way to herd immunity.