Potential role of Bacillus Calmette-Guérin (BCG) vaccination in COVID-19 pandemic mortality: Epidemiological and Immunological aspects.

SARS-CoV-2 had already killed more than 400,000 patients around the world according to data on 7 June 2020. Bacillus Calmette-Guérin (BCG) vaccine is developed from live-attenuated Mycobacterium bovis, which is a microorganism found in a cow. Discovered by Dr. Albert Calmette and Camille Guérin since 1921, the BCG has served as a protection against tuberculosis and its complications. It is noticeable that countries which use mandatory BCG vaccination approach had lower COVID-19 infection and death rate. Current review aims to clarify this issue through epidemiological illustration of correlation between national BCG immunization and COVID-19 mortality, in addition to biological background of BCG-induced immunity Epidemiological data shows that universal BCG policy countries have lower median mortality rate compare to countries with past universal BCG policy and non-mass immunization BCG. (18 May 2020). Still, the links between BCG vaccination and better COVID-19 situation in certain countries are unclear, and more data on actual infection rate using SAR-CoV-2 antibody testing in large population sample is crucial for disease spreading comparison. Two immunological mechanisms, heterologous effects of adaptive immunity and trained innate immunity which induced by BCG vaccination, may explain host tolerance against COVID-19 infection, however, there is no direct evidence to support this biological background. Clinical trials related to BCG vaccination against COVID-19 are under investigation. Without a strong evidence, BCG must not be recommended for COVID-19 prevention, although, this should not be absolute contraindication. Risk of local and systemic complications from the vaccine should be informed to individual, who request BCG immunization.

Effects of secondhand smoke exposure on asthma morbidity and health care utilization in children: a systematic review and meta-analysis.

BACKGROUND: Secondhand smoke (SHS) exposure can trigger asthma exacerbations in children. Different studies have linked increased asthma symptoms, health care use, and deaths in children exposed to SHS, but the risk has not been quantified uniformly across studies. OBJECTIVE: To perform a systematic review and meta-analysis to evaluate and quantify asthma severity and health care use from SHS exposure in children. METHODS: A systematic review was undertaken to assess the association between asthma severity and SHS in children. Inclusion criteria included studies that evaluated children with SHS exposure and reported outcomes of interest with asthma severity including exacerbations. Random effect models were used to combine the outcomes of interest (hospitalization, emergency department or urgent care visits, severe asthma symptoms, wheeze symptoms, and pulmonary function test results) from the included studies. RESULTS: A total of 1,945 studies were identified and 25 studies met the inclusion criteria. Children with asthma and SHS exposure were twice as likely to be hospitalized for asthma (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.20-2.86, P = .01) than children with asthma but without SHS exposure. SHS exposure also was significantly associated with emergency department or urgent care visits (OR 1.66, 95% CI 1.02-2.69, P = 0.04), wheeze symptoms (OR 1.32, 95% CI 1.24, 1.41, P < .001), and lower ratio of forced expiratory volume in 1 second to forced vital capacity (OR -3.34, 95% CI -5.35 to -1.33, P = .001). CONCLUSION: Children with asthma and SHS exposure are nearly twice as likely to be hospitalized with asthma exacerbation and are more likely to have lower pulmonary function test results.