Skip to main content

COVID-19 pneumonia severity and BCG vaccination

A recent research paper published in the BSI’s official journal Clinical & Experimental Immunology explored the relationship between BCG vaccination status and COVID-19 disease severity in patients from a country with a long-standing BCG vaccination programme.

The effect of BCG vaccination on COVID-19 

COVID-19 severity and death differ between countries with different public health policies. It was suggested that a country’s BCG vaccination policies can affect COVID-19 outcomes. This is because countries such as Italy, where BCG vaccination is not mandatory, were severely affected by COVID-19 whereas countries such as Japan, who have a BCG vaccination policy, experienced less severe outbreaks.

The BCG vaccine protects against the bacteria that causes tuberculosis but also improves the immune response to other respiratory viral infections such as influenza. The potential protection that the BCG vaccine offers against SARS-CoV-2, the virus that causes COVID-19, is unknown.

What experiments were carried out in this study?

Researchers recruited 123 adults aged 19–87 years, who had been diagnosed with COVID-19 pneumonia in a hospital in Istanbul, Turkey between March and June 2020. Patients were classified as having either mild or severe pneumonia and their sociodemographic characteristics, body-mass index, smoking history, comorbid diseases, and symptoms were collected. Patients’ BCG vaccination history was determined based on subjects’ self-declaration together with observation of vaccine scar by consultant pulmonologist

Statistical analysis was carried out to determine the effects of age, gender, income, BCG vaccination status, smoking, diabetes and hypertension on the likelihood of severe COVID-19 pneumonia.

What did the results of this study suggest?

The analysis revealed that increased age and low-income were associated with severe COVID-19 pneumonia in those patients. BCG vaccination status was not associated with the severity of COVID-19 pneumonia experienced by patients.

What can we conclude from this study?

This study was the first to look at the individual level of BCG vaccination and COVID-19 severity, rather than national levels of vaccination. The results are important to understand how BCG vaccination does not affect COVID-19 pneumonia severity. However, the sample size was small and, as Turkey has a routine BCG vaccination programme, there’s a limited number of individuals who have not been vaccinated. The study confirmed that age and socioeconomic inequalities affect COVID-19 severity, but they were not able to follow-up patients to better understand how those factors affect recovery time, rate of admission into intensive care or mortality.


Aksu, K., Naziroğlu, T. and Özkan, P. (2020), Factors determining COVID‐19 pneumonia severity in a country with routine BCG vaccination. Clinical & Experimental Immunology. doi:10.1111/cei.13507

Paper first published 19 August 2020


Summary author Erika Aquino, BSI Public Engagement Manager