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The BCG vaccine given to every British teenager between 1953 and 2005 to protect against tuberculosis could offer protection against Covid-19, a new study has found.  

Bacillus Calmette-Guerin (BCG) was first mass produced in 1924, and widespread vaccination for secondary school children was only halted in the UK when TB was effectively eradicated.

Academics in the US compared the BCG jab's popularity in several countries with each nation's coronavirus outbreak — including both infections and deaths — and found a clear link between the vaccine and a lower mortality rate from Covid-19.

When differences in social, economic, and demographics were taken into account, scientists found that where there was a 10 per cent greater prevalence of the BCG vaccine there was also a 10.4 per cent reduction in COVID-19 mortality. 

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The Bacillus Calmette-Guérin (BCG) vaccine (pictured) is used to fend off tuberculosis (TB) but it has long been known to have other health benefits, including helping a person's immune system to fend off respiratory infections

Children in the UK were required to have the injection by the age of 14, making the last cohort to receive the immune-boosting jab around 29 to 30 now. 

BCG is still widely used in some countries around the world where there is a higher risk of TB, but in the UK only at-risk individuals, such as babies living with infected relatives and children in some BAME groups, receive the jab. 

Professor Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases at the University of Nottingham who was not involved in the research, said: 'Within the UK, most people over 30 and under 80 will have had BCG in the schools programme.

'Many children in the BAME groups will have continued to be vaccinated at birth, although people born outside the UK may not have been vaccinated.

'There are also many different BCGs around the world.' 

Coronavirus have spikes on their surfaces which help them infect cells. The spike on SARS-CoV-2 (right), the virus causing the current pandemic, is very similar to the spike of a different coronavirus seen in bats (left). However, it is 1,000 times better at infecting human cells 

The latest study, from academics at Virginia Polytechnic Institute and State University and the National Institutes of Health, has been peer-reviewed and published in the journal PNAS. 

Writing in their paper, they say: 'This epidemiological study assessed the global linkage between BCG vaccination and Covid-19 mortality. 

'Signals of BCG vaccination effect on Covid-19 mortality are influenced by social, economic, and demographic differences between countries. 

'After mitigating multiple confounding factors, several significant associations between BCG vaccination and reduced Covid-19 deaths were observed.' 

The BCG vaccine was invented a century ago and gives immunity to tuberculosis (TB) — a bacterial infection — but it is known to have other benefits.  

Previous trials discovered people who receive the jab, which costs as little as £30, have improved immune systems and are able to protect themselves from infection. 

For example, in a trial among Native Americans, BCG vaccination in childhood was able to offer protection against TB up to 60 years after vaccination. 

These so-called off-target effects include enhanced protection against respiratory diseases, and have been recognised by the World Health Organization (WHO).

BCG has been used for more than 90 years but exactly how it works still remains a mystery. 

And how it may protect against Covid-19 is an even larger enigma. 

The best theory is that the vaccine, which contains a live bacteria called Mycobacterium, boosts the innate immune system, making it more effective. 

Ongoing studies into whether BCG can help fend of Covid-19 are ongoing in Holland and Australia but, until these results are available, the researchers of the latest study say even transient immunity could help fight the pandemic. 

'[The BCG vaccine] may be useful in individuals at high risk, such as health workers, first responders, and police officers, or those with preexisting conditions such as obesity, diabetes, or cardiovascular disease,' say researchers.

'Similarly, even enhanced unspecific immunity through BCG vaccination in vulnerable age groups could ameliorate severe Covid-19. 

'Temporarily induced trained immunity could buy time until specific vaccines and/or effective treatments against SARS-CoV-2 infections become available.' 

How useful this short-term immunity would be in the current pandemic, remains to be seen.  

Professor Ben Neuman, Visiting Associate Professor at the University of Reading, say that while there is a clear benefit to using BCG to protect against TB, 'it is questionable whether a tuberculosis vaccine would be seen as a viable form of long-term immune system modification for use against Covid-19'.