BCG trials hold promise, but don't try this at home, say scientists

In the rush for treatments and vaccines, names of existing medications are flying about, with some even flying off the shelves.

The Covid-19 pandemic has put the lay public at the mercy of their own ignorance as they try get their hands on drugs being trialed by scientists, and punted by presidents.

This week, the governor of Utah in the US had to ask for a refund after blowing $800,000 on a stash of the anti-malarial chloroquine after it was erroneously hyped as helper in the fight against Covid-19.

Even where hope springs eternal, scientists are calling for calm before anything has been proved beyond reasonable doubt.

The latest warning comes in the form of a letter to The Lancet cautioning against unregulated use of the BCG vaccine.

Tongues have been wagging about the vaccine, which is usually given to newborn babies to guard against tuberculosis in high risk countries.

Believing it could help adults in high risk settings like hospitals, scientists have embarked on trials to see if the vaccine given to adult healthcare workers can offer a level of protection against the virus.

However, those involved in carrying out the trial have put out a public call warning other healthcare professionals and members of the public not to seek the vaccine on their own.

“BCG vaccine has beneficial nonspecific effects on the immune system that protect against a wide range of other infections [besides TB] and are used routinely to treat bladder cancer,” Professor Nigel Curtis, who is heading up the Australian trial, said in The Lancet.

This has led to the suggestion that vaccination with BCG might have a role in protecting healthcare workers and other vulnerable individuals against severe coronavirus disease. 

BCG is favoured in the fight against respiratory infections. In Guinea-Bissau, it reduced all-cause neonatal mortality by 38%, mainly because there were fewer deaths from pneumonia and sepsis.

In South Africa, it reduced respiratory tract infections by 73% in adolescents, according to Curtis.

It has been shown to reduce “the severity of infections” by other viruses with a similar structure to the novel coronavirus in controlled trials. 

“Many of the mechanisms underlying the beneficial off-target effects of the BCG vaccine are now understood,” said Curtis and the other authors.

“The BCG vaccine and some other live vaccines induce changes that enhance the innate immune response to subsequent infections, a process termed trained immunity.”

In other words, it’s looking hopeful.

However, very importantly, it should only be used in the controlled trials that are underway.

These are taking place in both the Netherlands and Australia to see if the vaccine “reduces the incidence and severity of Covid-19 in healthcare workers, and the effect this has on time away from work”.

Curtis said: “Until these trials are complete, it is very important to adhere to the World Health Organisation’s recommendation that the BCG vaccine is used for Covid-19 only in randomised controlled trials.”

That’s because it is “already in short supply”, and whether it will even be effective remains unknown.

Furthermore, use of the vaccine could “engender a false sense of security”, and its use can only be safely monitored in the context of the randomised trials.

If the BCG vaccine can “bridge the gap before a disease-specific vaccine is developed, this would be an important tool in the response to Covid-19 and future pandemics”.

The fact is, we don’t know for sure yet.

There is hope, but until hope turns to proof, stay calm and carry on.