A study published yesterday in The Lancet discovered that only 4.6% of questionnaire respondents across Spain had antibodies against SARS-CoV-2, the virus that causes COVID-19, in their serum by immunoassay, while 5% tested positive on a point-of-care finger stick test.Also, a study yesterday in Clinical Infectious Diseases reported that 19 (7.6%) of 249 frontline healthcare workers in Nashville, Tennessee, tested positive for antibodies against the novel coronavirus, with only 11 of them reporting COVID-19 symptoms.Natural herd immunity still far offIn the first study, conducted from Apr 27 to May 11, researchers in Madrid tested 61,075 participants with a point-of-care test, 51,958 with an immunoassay, and some with both.