BCG vaccine also boosts non-TB immune system: Study

Filip Vukasin

18/08/2022 4:38:50 PM

But while BCG is the world’s most commonly used vaccine, it has not been routinely administered in Australia since 1985.

BCG vaccine
While most of the world routinely vaccinates their population with BCG, North America, New Zealand, Western Europe and Australia do not.

A Melbourne-led trial has found the Bacille Calmette-Guérin (BCG) vaccine for tuberculosis (TB) confers a number of immune-boosting benefits for more than 14 months post-vaccination by altering monocytes via a ‘trained immunity response’.
But while previous research has shown ‘off-target’ benefits from BCG vaccine, which are those unrelated to TB, the latest study adds to knowledge about duration and how this takes place.
It involved 130 infants and cell dish models, which were used to study the immune system’s response to BCG vaccine. Those randomised to be vaccinated received their BCG within 10 days of birth.
Professor Boris Novakovic, a molecular biologist at Murdoch Children’s Research Institute (MCRI), was a co-author on the study.
‘We know that BCG vaccine improves all-cause mortality from trials in Africa,’ he told newsGP.
‘We wanted to see from this trial, how long the immune memory lasts. Anecdotally, doctors say it lasts over one year.
‘We found this signature on monocytes lasted about 14 months.’
The new analysis shows that BCG exposure induces a persistent change in active histone modifications, DNA methylation, transcription, and adenosine-to-inosine RNA modification in human monocytes.
Genes associated with this epigenetic signature are involved in viral response pathways, consistent with the reported off-target protection against viral infections in neonates, adults, and the elderly.
Last year, studies in Africa also showed that neonatal BCG vaccination confers protection against non-tuberculous infectious diseases in early childhood.
This off-target protection of BCG against unrelated infections has also been replicated in other trials that show BCG-vaccinated adults have better outcomes from yellow fever vaccine side effects and malaria infection, as well as protections against viral respiratory tract infections in the elderly.
But while most of the world routinely vaccinates their population with BCG, North America, New Zealand, Western Europe and Australia do not.
Might there be a benefit to adding BCG vaccine to the national immunisation schedule?
‘We are an outlier with BCG vaccination worldwide,’ Professor Novakovic said.
‘In [Australia], children are less likely to die from infectious diseases. So there have been other studies looking to see if there might be an effect on allergy.
‘There was no effect on allergies generally, but there was on babies that were high risk.’
BCG vaccine is one of the oldest vaccines still in routine use and remains the most commonly administered vaccine worldwide. Multiple different BCG strains exist and are in use. It is usually given at birth and is most effective in preventing childhood meningeal and miliary tuberculosis.
In Australia, there is a disparity between rates of TB in Indigenous and non-Indigenous Australians.
However, the BCG vaccine is usually offered to high risk individuals through travel clinics or hospitals, or to individuals who want it prior to travel to an endemic country.
Other studies into off-target benefits have led to large-scale clinical trials of BCG vaccination in healthcare workers to reduce the burden of severe COVID.
Long term studies regarding off-target effects from BCG vaccine are due to continue, but it is also not the only vaccine that can have off-target benefits.
Professor Novakovic points to the known effects of other vaccines on training the immune system, including MMR vaccine and DTPa.
‘This concept of immune training has been around for about 10 years,’ he said.
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