Reply to Patella et al. and Lindestam Arlehamn et al.: Complex pandemic dynamics and effect of bacillus Calmette–Guérin (BCG) vaccination on COVID-19 prevalence and mortality

Abstract

In agreement with our published results (1), the epidemiological analysis by Lindestam Arlehamn et al. (2), with COVID-19 data from April 22, 2020, found a significant negative correlation ( P = 0.0006) between mean bacillus Calmette–Guérin vaccination coverage and deaths from COVID-19. However, this correlation did not hold when the authors used updated mortality data from August 1, 2020 (2). Two major factors determine the probability that a person will die from COVID-19: first, whether the person becomes infected; second, for those who become infected, how well they respond to the infection, and this is determined by biological and social variables such as age, gender, preexisting conditions, immunological history (such as bacillus Calmette–Guérin vaccination), and the access and efficacy of medical interventions. The dynamics of the COVID-19 pandemic are complex, and as time goes by, the degree of success of social distancing strategies predominate as the major determinant of the number of people that become infected and those that ultimately die from the infection. For example, COVID-19 mortality in the United States decreased from 6.1% on May 12 to 3.2% on August 12, 2020 (3), due, in part, to the large number of young people infected between June and August (4). We compared the mortality rates in different countries during the first 25 to 30 d of the pandemic, because the infections leading to those early deaths took place before … [↵][1]1To whom correspondence may be addressed. Email: cbarillas{at}niaid.nih.gov. [1]: #xref-corresp-1-1