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Covid-19: preparedness, decentralisation, and the hunt for patient zero

BMJ 2020; 368 doi: (Published 28 February 2020) Cite this as: BMJ 2020;368:bmj.m799

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Re: Covid-19: preparedness, decentralisation, and the hunt for patient zero

Dear Editor

I am very impressed regarding editorial comments (1). In this situation, the ecological association between BCG vaccination and COVID-19 infection might give us an additional strategy.

Moorlag et al. reviewed non-specific protection induced by Bacillus Calmette-Guérin (BCG) vaccination against viral infections, including possible mechanisms of action (2). The authors speculated that the effects might partly be mediated via induction of innate immune memory and heterologous lymphocyte activation, which accelerated cytokine production, increased macrophage activities and T-cell responses. There have been many studies that BCG vaccination impacts the immune response to subsequent infections, resulting in reduced morbidity and mortality. Recently, the protective effect of BCG on COVID-19 infection in humans has been speculated by nationwide ecological inverse association between past history of BCG vaccination and COVID-19 infection-related morbidity and mortality.

Murin et al. reviewed antibody responses to viral infections by selecting three enveloped viruses (3). They mentioned that the ability to isolate antigen-specific B-cells and rapidly solve structures of functional, monoclonal antibodies in complex with viral glycoprotein surface antigens has become popular information of the sites of vulnerability on viruses. Shann had been described the concept of non-specific effects of vaccines (4), and urgent actions are required if BCG vaccine can be applied to inhabitants having risk of COVID-19 infection.


1. Carinci F. Covid-19: preparedness, decentralisation, and the hunt for patient zero. BMJ. 2020;368:bmj.m799. doi: 10.1136/bmj.m799

2. Moorlag SJCFM, Arts RJW, van Crevel R, et al. Non-specific effects of BCG vaccine on viral infections. Clin Microbiol Infect. 2019;25(12):1473-1478.

3. Murin CD, Wilson IA, Ward AB. Antibody responses to viral infections: a structural perspective across three different enveloped viruses. Nat Microbiol. 2019;4(5):734-747.

4. Shann F. The non-specific effects of vaccines. Arch Dis Child. 2010;95(9):662-667.

Competing interests: No competing interests

17 April 2020
Tomoyuki Kawada
Nippon Medical School
1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan