{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,26]],"date-time":"2025-11-26T16:41:35Z","timestamp":1764175295731,"version":"build-2065373602"},"reference-count":142,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2022,9,30]],"date-time":"2022-09-30T00:00:00Z","timestamp":1664496000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Despite controversy over the protective effect of the BCG (Bacille Calmette-Gu\u00e9rin) vaccine in preventing pulmonary tuberculosis (TB) in adults, it has been used worldwide since 1921. Although the first reports in the 1930s had noted a remarkable decrease in child mortality after BCG immunization, this could not be explained solely by a decrease in mortality from TB. These observations gave rise to the suggestion of nonspecific beneficial effects of BCG vaccination, beyond the desired protection against M. tuberculosis. The existence of an innate immunity-training mechanism based on epigenetic changes was demonstrated several years ago. The emergence of the pandemic caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2) in 2019 revived the debate about whether the BCG vaccine can affect the immune response against the virus or other unrelated pathogens. Due to the mortality of the coronavirus disease (COVID-19), it is important to verify each factor that may have a potential protective value against the severe course of COVID-19, complications, and death. This paper reviews the results of numerous retrospective studies and prospective trials which shed light on the potential of a century-old vaccine to mitigate the pandemic impact of the new virus. It should be noted, however, that although there are numerous studies intending to verify the hypothesis that the BCG vaccine may have a beneficial effect on COVID-19, there is no definitive evidence on the efficacy of the BCG vaccine against SARS-CoV-2.<\/jats:p>","DOI":"10.3390\/vaccines10101641","type":"journal-article","created":{"date-parts":[[2022,10,11]],"date-time":"2022-10-11T06:13:27Z","timestamp":1665468807000},"page":"1641","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["BCG and SARS-CoV-2\u2014What Have We Learned?"],"prefix":"10.3390","volume":"10","author":[{"given":"Jakub","family":"Kulesza","sequence":"first","affiliation":[{"name":"Department of Internal Diseases and Clinical Pharmacology, Medical University of Lodz, Kniaziewicza 1\/5, 91-347 Lodz, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ewelina","family":"Kulesza","sequence":"additional","affiliation":[{"name":"Department of Rheumatology and Internal Diseases, Medical University of Lodz, \u017beromskiego 113, 90-549 Lodz, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Piotr","family":"Kozi\u0144ski","sequence":"additional","affiliation":[{"name":"Tuberculosis and Lung Diseases Outpatient Clinic, Health Facility Unit in \u0141\u0119czyca, Zachodnia 6, 99-100 \u0141\u0119czyca, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wojciech","family":"Karpik","sequence":"additional","affiliation":[{"name":"Department of Immunology and Infectious Biology, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12\/16, 90-237 Lodz, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3659-8115","authenticated-orcid":false,"given":"Marlena","family":"Broncel","sequence":"additional","affiliation":[{"name":"Department of Internal Diseases and Clinical Pharmacology, Medical University of Lodz, Kniaziewicza 1\/5, 91-347 Lodz, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marek","family":"Fol","sequence":"additional","affiliation":[{"name":"Department of Immunology and Infectious Biology, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12\/16, 90-237 Lodz, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,9,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"The Lancet (2016). 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