About 15 years ago I had sepsis. It struck out of the blue. In fact, the day beforehand I was pushing a wheelchair-bound friend around a park until, from one minute to the next I couldn’t take another step.

We managed to get home but that night I was wakened by severe pain in my left ankle and discovered it was swollen and blue. I called 999 and by the time I got to hospital, my organs were failing. My infected ankle was drained and I was on IV antibiotics for four weeks.

The culprit was Strep A. I was lucky. Globally every year, around half a million people, including many ­children and teens, die from Strep A infections, some of which lead to deadly sepsis or heart damage. There’s currently no available vaccine for it either.

The newly launched iSpy Network brings together 28 investigators to study Strep A from 11 countries ­worldwide. It includes experts in immunology, infectious diseases, epidemiology, vaccinology and ­experimental medicine led by Imperial College London alongside the ­University of California San Diego.

Imperial Professor Shiranee Sriskandan, who heads up one of two iSpy sub-networks, iSpy-LIFE, points to the deaths among children. She says: “The overwhelming burden of disease is shouldered by middle and low-income countries (LMICs), where we see more invasive disease and children getting persistent Strep A infections, which can lead to debilitating rheumatic heart disease.”

The iSpy Network collaborates with partners in The Gambia, South Africa, Brazil and Fiji to figure out the body’s immune response to Strep A and the most effective way to vaccinate against it.

Strep A commonly causes sore throat and skin infections in younger children and, more rarely, can trigger sepsis and toxic shock when the ­bacterium enters the bloodstream. Repeated Strep A infections can damage the valves of the heart, known as rheumatic heart disease (RHD), which affects an estimated 50 million people worldwide, with most living in LMICs.

Professor Liesl Zuhlke, a paediatric cardiologist at Cape Town University, emphasises that RHD patients they see in LMICs have advanced to heart failure. Many need cardiac surgery or IV treatment which often aren’t ­available, leading to long-term illness and death.

Professor Sriskandan adds: “It’s also unclear how overreaction by the immune system to StrepA – what we might call ‘bad’ immunity – leads to RHD and how that differs from the ‘good’, protective immunity we’d like to see.”

The iSpy-LIFE sub-network will investigate how “good” immunity to Strep A develops in children and learn how a vaccine might accelerate that immunity in all youngsters.