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The BCG World Atlas: A Database of Global BCG Vaccination Policies and Practices [1]

['Alice Zwerling', 'Department Of Epidemiology', 'Biostatistics', 'Occupational Health', 'Mcgill University', 'Montreal', 'Respiratory Epidemiology', 'Clinical', 'Research Unit', 'Montreal Chest Institute']

Date: 2022-09 

Citation: Zwerling A, Behr MA, Verma A, Brewer TF, Menzies D, Pai M (2011) The BCG World Atlas: A Database of Global BCG Vaccination Policies and Practices. PLoS Med 8(3): e1001012. https://doi.org/10.1371/journal.pmed.1001012 Published: March 22, 2011 Copyright: © 2011 Zwerling et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported in part by the Public Health Agency of Canada (PHAC) and a team award from the National Sanitarium Association (NSA), Canada. AZ is supported by a Canadian Institutes of Health Research (CIHR) Doctoral research award. MP is a recipient of a CIHR New Investigator Award and DM & MB are recipients of Fonds de la recherche en santé du Québec (FRSQ) career awards. These funding sources had no role in the design, execution or publication of this study. Competing interests: No financial conflicts. Madhukar Pai serves as an external consultant for the Bill & Melinda Gates Foundation (BMGF). BMGF had no involvement in this manuscript. Madhukar Pai is a member of the PLoS Medicine Editorial Board. Abbreviations: BCG, Bacille Calmette-Guérin; IGRA, interferon-gamma release assay; LTBI, latent tuberculosis infection; TB, tuberculosis; TST, tuberculin skin test; WHO, World Health Organization Provenance: Not commissioned; externally peer reviewed.

Summary Points Despite nearly a century of use, the Bacille Calmette-Guérin (BCG) vaccine continues to be controversial, with known variations in BCG substrains and vaccine efficacy.

Because vaccination policies and practices vary across time and countries, we created the first searchable, online, open access database of global BCG vaccination policy and practices, the BCG World Atlas (http://www.bcgatlas.org/), which contains detailed information on current and past BCG policies and practices for over 180 countries.

The Atlas is for clinicians, policymakers, and researchers and provides information that may be helpful for better interpretation of tuberculosis (TB) diagnostics as well as design of new TB vaccines.

Tuberculosis: A Global Threat Tuberculosis (TB) remains one of the major causes of infectious morbidity and mortality globally, claiming millions of lives every year. Approximately one-third of the world's population is estimated to be infected with Mycobacterium tuberculosis, giving rise to 9.4 million new cases of active TB disease each year [1]. The majority of the TB burden exists in 22 high-burden countries, but with immigration and global travel TB is difficult to eliminate from any one country [1]–[4]. The Bacille Calmette-Guérin (BCG) vaccine, first introduced in 1921, continues to be the only vaccine used to prevent TB [5],[6]. Despite nearly a century of use, BCG remains controversial, with known variations in BCG substrains, vaccine efficacy, policies, and practices across the world. Global information on BCG policies and practices may be useful for clinical interpretation of diagnostic tests as well as in the design of novel TB vaccines that are under development.

BCG: A Range of Global Policies While most experts agree that BCG is efficacious against severe forms of childhood TB, its efficacy against TB in adults is highly variable [7]. As a result of the uncertain efficacy of the BCG vaccine, countries have developed very different BCG vaccination policies. Some countries, such as the United Kingdom, have or have had universal BCG vaccination programs, while others (including Canada and the United States) either only recommended BCG for high-risk groups or did not advocate BCG countrywide. The Canadian situation was further complicated by differing policies across provinces, where some provinces underwent mass vaccination programs and others did not. In addition, BCG vaccination policies have varied by the number of doses used, the age at which vaccination was given, and the methods used to deliver the vaccine (although most countries today use only the intradermal route) [8]. Vaccination practices also have changed within and across countries over the years, reflecting changes in evidence, health policy, public perception, increasing or decreasing TB incidence, and HIV incidence. As a result of these changes to the BCG policies in various countries, it is necessary to not only know the current BCG vaccination policies but also past policies and applicable changes when dealing with adults who received BCG vaccination in childhood. Since the publication of the M. tuberculosis genome, comparative genomic studies have documented that BCG vaccine strains have evolved and differ from each other and from the original BCG first used in 1921 [9]. Because these genetic differences affect antigenic proteins, these changes may translate into differences in efficacy and effect on the tuberculin skin test (TST) [10],[11]. Work done by Ritz and Curtis looking at global BCG strain variations demonstrates the diversity of strains used by different countries and even within the same countries [12]. They found that 44% (83/188) of countries reported using more than one BCG strain type during an interval of only 5 years. This highlights the importance of documenting BCG vaccination practices for both clinical and research purposes. Clinicians cannot be expected to know BCG practices in all countries, and immigrants themselves may not know about the vaccination policies in their countries of birth (most adult immigrants are unlikely to retain childhood vaccination records). Information on diversity of BCG policies between countries and across time may be helpful for better interpretation of TB diagnostics as well as design of new TB vaccines. To our knowledge, there is no single, comprehensive, searchable database of BCG policies and practices (past and present) across the world. We developed the “BCG World Atlas: A Database of Global BCG Vaccination Policies and Practices,” a database containing BCG information from each country across all world regions (http://www.bcgatlas.org/). Figure 1 shows the homepage of the Atlas. To make this resource practical and useful for clinicians, public health practitioners, and researchers alike, our database captures both present and previous policy and practices within a country, as well as any applicable changes. PPT PowerPoint slide

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TIFF original image Download: Figure 1. Home page of the BCG World Atlas ( Home page of the BCG World Atlas ( http://www.bcgatlas.org/ ) and example of BCG policies and practices in Japan. https://doi.org/10.1371/journal.pmed.1001012.g001

Assembling the Database Detailed information on past and present BCG vaccination policies and practices were collected from as many countries as possible by one of three methods. First, short respondent-completed questionnaires were sent out to at least two individuals in each country. Questionnaires were sent to experts in TB research, TB control programs, or public health/vaccination programs. Whenever possible, an attempt was made to collect two completed questionnaires from each country in order to validate the data. Questionnaires were available in English, French, and Spanish, and were designed to capture both current policy and actual BCG practices, as well any applicable changes that had occurred over the last 25 years. Detailed questions asked for information concerning past as well as current practices, the timing and nature of changes to the policies and or practices, repeat, multiple, or booster shots, information concerning tuberculin skin testing in conjunction with BCG vaccination, influence of HIV on the decision to vaccinate, and vaccine strain differences. A total of 89 completed questionnaires were received over a 2-year period. Second, data were abstracted from published papers, reports, and available government policy documents retrieved through literature searches on PubMed and via the World Wide Web. Third, we used immunization data available from the World Health Organization Vaccine Preventable Diseases Monitoring System (http://apps.who.int/immunization_monitoring/en/globalsummary/ScheduleSelect.cfm), which provide basic information on all vaccines currently in use in each country [13]. Based on the data generated by all methods, countries were grouped into three main categories: A), the country currently recommends universal BCG vaccination at a certain age; B), the country used to recommend universal BCG vaccination but currently does not; or category C), BCG vaccination is recommended only for selected high-risk groups or was never recommended.

Open Access through an Interactive Web Site The Atlas is an interactive Web site that allows users to select and view information concerning a country's past and current BCG vaccination policy either by clicking on an interactive map or by selecting the country of interest from a drop-down list (Figure 1). The Web site is available to the public and is free of charge. Over the past year (during its beta phase), we have recorded over 6,000 visits to the site, with a steady increase in traffic over time.

Implications for Immunization Strategies Recently there has been renewed interest in developing novel vaccines for TB. According to the Global Plan to Stop TB, 2006–2015, “effective TB vaccines will be an essential component of any strategy to eliminate tuberculosis (TB) by 2050” [33]. In 2009, at least six different vaccine candidates completed Phase I clinical trials, and three are currently in Phase II [18]. Novel vaccine candidates include both live and sub-unit vaccines. Many employ a heterologous “prime-boost” strategy that complements the existing immune response to BCG. Either the existing BCG or a new recombinant BCG is administered first, and then the new vaccine serves as a “booster”. Different vaccines are being developed that could be administered in infants and young children pre-exposure, and others as adjuvants to chemotherapy post-exposure. Given that novel vaccines may work to complement the existing BCG, it may be relevant to know what previous BCG vaccination individuals have had, how many and at what ages prior to administering novel “booster vaccines”. Similarly, we may be concerned that antigens from the primary vaccination with BCG may affect the booster vaccine. Therefore, in countries where revaccination with BCG was practiced, we might expect higher rates of Koch response, or delayed hypersensitivity response. In 2007, the WHO revised its policy on BCG vaccination of children with HIV, making HIV infection in infants a full contra-indication for BCG vaccination, even in settings highly endemic for TB [34]. In 2008, the IUATLD BCG Working Group published a consensus statement supporting the revised WHO BCG vaccination policy, but recommended that current universal BCG immunization of infants continue in countries highly endemic for TB until countries have programs in place for implementing selective deferral of BCG vaccination in infants exposed to HIV [35]. As countries respond to these new global recommendations, changes in vaccination policies because of the HIV epidemic should be captured in future updates of the Atlas.

Conclusions Despite nearly a century of use, the BCG vaccine continues to be controversial, and policies and practices vary widely across the world. Many countries have experienced major changes in regards to revaccination over the past 20 years. The BCG World Atlas: A Database of Global BCG Vaccination Policy and Practices is an interactive Web site that attempts to provide the clinician, researcher, and pubic health practitioner alike with resources and information necessary to interpret current and novel TB diagnostics and conduct fruitful research on novel vaccines. Most critically, this is a useful resource for the TB community and is publicly available free of charge through an easy-to-use Web site.

Acknowledgments The authors are grateful to a large number of colleagues from around the world for their contributions to this BCG Atlas. The authors welcome input that will help improve the Atlas, especially from countries that are currently not covered.

Author Contributions Wrote the first draft of the paper: AZ MB MP. Contributed to the writing of the paper: AZ MB AV TB DM MP. ICMJE criteria for authorship met: AZ MB AV TB DM MP. Agree with results and conclusions: AZ MB AV TB DM MP. Built and programmed the Web site: AV. Provided supervision: MB DM MP.

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[1] Url: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001012

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