On Mar. 17, 2020, a small study of macaques found they don’t develop a coronavirus infection the second time they are exposed, supporting the idea of using plasma from recovered patients as a treatment for COVID-19.

The research, posted as a preprint to bioRxiv Mar. 14, had yet to undergo peer review. To the authors, the results indicated that reports of some COVID-19 survivors being ‘re-infected’ a second time can be explained by issues with testing rather than a failure to develop immunity.