BCG vaccination early in life does not improve COVID‐19 outcome of elderly populations, based on nationally reported data

Abstract

Significance and Impact of the Study: It has been suggested in the recent literature that some countries have lower case rates or death rates of Covid-19 as a result of large-scale BCG vaccination programs. This has resulted in the initiation of clinical trials to assess if the vaccine can act as a prophylactic or ameliorate the disease. However, by comparing countries that are well into the epidemic and have different (current or past) BCG vaccination practices, we conclude that there is currently no compelling evidence of any such protective effect.

Why Are COVID-19 Mortality Rates by Country or Region So Different?: An Ecologic Study of Factors Associated with Mortality from Novel Coronavirus Infections by Country

“…[5][6][7] However, this hypothesis has proven to be unreliable, as some studies have shown conf lictive results. 8,9 Although, BCG vaccination coverage was not statistically significant in the current study, mortality rate was found to be low in countries that implemented BCG vaccination (Fig. 6).…”

“…There are articles that mortality or morbidity from COVID-19 by country is associated with Bacille de Calmette et Guérin (BCG) coverage and smoking rates. [3][4][5][6][7][8][9] Report of a high incidence of Kawasaki disease-like symptoms among children affected by COVID-19 suggests a link between the two diseases. 10 Factors commonly associated with mortality include accessibility of healthcare, healthcare delivery systems, number of healthcare facilities and the healthcare professionals.…”

COVID-19 Infection and Previous BCG Vaccination Coverage in the Ecuadorian Population

“…These data could suggest a protective effect of BCG vaccination, but such studies cannot provide definitive proof of causality, owing to several inherent biases, including the quality of raw data COVID-19 reports [37], differences in the demographic and genetic structure of the populations, and the non-pharmaceutical interventions being adopted (e.g., quarantine or social distancing, the moment during the pandemic in which the data are analyzed, age of vaccination and changes in this regard (because BCG has better epigenetic activity at an early age, when the body is more susceptible to these changes being made), the time needed for the country to have appropriate coverage, and variations in coverage in terms of geographic areas) [23]. As of 7 November 2020, the effect of prophylactic BCG vaccination on COVID-19 outcomes is being investigated in 18 registered clinical trials (on clinicaltrials.gov).…”

“…Appropriate epidemiological pandemic control and differences in policies regarding the age of vaccination and when countries adopted nationwide vaccination (and whether it was adopted at all) make it impossible to identify a clear correlation. A recent study by Wassenaar et al indicates the presence of a high attack rate even in countries with high BCG coverage [23]; however, we think that it is extremely important to analyze this phenomenon in more depth, particularly by country or in even smaller geographic units, in order to identify possible correlations and minimize confusion.…”

Pandemic-stage propagation dynamics in South Africa suggest pre-existing cross-reactive protection against severe Covid-19

“…All scenarios of reinfection also require assuming a low IFR in order to replicate the observed attributes of the outbreak. Introduction In the early stages of the Covid-19 pandemic it was suggested that population-wide vaccination programs such as for Bacille Calmette-Guérin (BCG) vaccines may have conferred trainedimmunity to SARS-CoV-2 (O'Neill and Netea, 2020), but later assessments provide evidence to the contrary (Lindestam Arlehamna et al, 2020;Wassenaar et al, 2020). It has also been suggested that previous exposure to common cold cornaviruses could result in cross-reactive Tlymphocyte immunity to SARS-CoV-2 (Braun et al, 2020;Sette and Crotty, 2020).…”