This paper in Lancet is a meta-review of the value of social distancing and wearing masks. (Lancet Paper) That means it is not original research but the authors search for and select other research on the topic and then attempt to synthesize the results in a meta-analysis, always a tricky undertaking. The focus was on studies relating to coronaviruses. The studies did not involve actual physical studies of the transmission of the virus. They were inferring potential risk of transmission for infected individuals depending on whether they were using protective gear. The authors found that distancing of 1 meter or more was more protective than less than 1 meter. They found that masks generally limited transmission, at least if they were N95 masks, and that eye protection also could limit transmission. But they note the evidence is largely from non-rigorous studies and randomized trials would be needed for definitive evidence. In regard to masks they noted several issues, including discomfort, skin breakdown, difficulty communicating clearly and if worn by providers, a perceived lack of empathy.
Two more papers looking at antibody presence among health care workers. The first, from China, looked at prevalence among 797 asymptomatic staff and found that 35 were positive for covid-19 antibodies. Most had been wearing extensive protective equipment around coronavirus patients. (Medrxiv Paper) The second is from workers in a hospital in New York City. 285 persons were tested and 33% tested positive, with three more testing weakly positive. All had been working and none reported any significant disease symptoms. (Medrxiv Paper)
Yet another paper on antibody prevalence looked at health care workers and their household members. 232 people in total were tested and 30 had tested positive for coronavirus on infection testing. Of these 27 had antibodies, 2 had weak antibodies and one was pregnant and apparently had a false positive infection test. Overall 33 of the subjects had antibodies and 40 had weak antibodies, but it is likely not enough time had passed since their infection for them to develop strong antibodies. 53% of those who had shared a household with a worker with confirmed coronavirus developed antibodies, although most of these persons had been asymptomatic. (Medrxiv Paper)