A solid epidemiological study from deCODE in Iceland was recently published in The New England Journal of Medicine. Population prevalence of SARS-CoV-2 positive tests in Iceland? 0.8% A separate serostudy from New York City? ~21%. This isn't quite an apples to apples comparison, as the two tests used and the study designs are completely different. There are also significant questions around the antibody testing used, and reliability. Even assuming significant noise in the numbers, the difference is striking.
Key takeaways from the robust Icelandic study:
- 43% of positive participants reported no symptoms at testing, though some may have gone on to later develop symptoms.
- Testing had been carried out for a month before the first positive.
- Over the course of the study, the percent positive (that 0.8%) remained stable, while overall respiratory symptoms decreased, possibly indicating that distancing and other measures were more broadly reducing the spread of seasonal respiratory infections.
- An interesting observation that those concerned about having an infection with mild symptoms may be more likely to seek out testing probably impacts both study's findings.
Key takeaway from the New York data:
- Antibody testing is not ready to be used as a benchmark for reopening the economy as the question of durable immunity to SARS-CoV-2 remains hotly debated.
Both are worth the read. Comment below with any questions, and I'll try to get them answered for you.