A groundbreaking study has claimed that the key to saving the lives of newborns is found in just half a teaspoon of blood.

Research has revealed dramatic changes in the immune systems of newborns, which scientists say could transform our understanding of disease in babies.

Co-led by the MRC Unit The Gambia, at London School of Hygiene & Tropical Medicine, and published in Nature Communications, the research revealed changes in development pathways within the cells of newborns related to fighting infection.

Researchers took blood samples from babies in a health centre in the Gambia, at birth and then again at either one, three or seven days old. They found thousands of changes in gene expression and in components related to immunity in babies in the first week of life. They then compared the findings with those in samples taken from a group of babies in Papua New Guinea. They concluded the changes were not random, but age-specific.

One of the biggest challenges in gathering data on newborn development has been how to collect blood samples large enough to profile tiny babies. The researchers overcame this by refining their techniques to allow smaller samples.

Researchers said they hoped the findings would inform vaccine studies targeted at newborns, the population most vulnerable to fatal infections, particularly in the developing world.

Senior author Beate Kampmann, professor of paediatrics at London School of Hygiene & Tropical Medicine, said: “Knowledge about key developmental processes during our earliest days remains sparse, but this study plugs some of those crucial gaps. This work is particularly important for vaccine research.

“Newborns have very limited protection from infection in early life and there is an urgent need to optimise protective measures, including vaccines, used in this age group.”

The first few days of life is a time of rapid biological change, as babies adapt to living outside their mother’s womb, in a world exposed to bacteria and viruses. Yet surprisingly little is known about these changes at a molecular level, said Kampmann.

The scientists were keen to work in a real-world situation, she said, in order to gain insight into infant immune development in a setting where new interventions could have the biggest impact on survival, paving the way to identifying newborns most at risk of disease, and to vaccine development that could benefit them.

Ofer Levy, of Boston children’s hospital, and a senior author on the paper, said: “Currently, most vaccines are developed by trial and error. We seek deep molecular insight into vaccine function in early life so we can better develop infant vaccines for the future.”

An estimated 5.4 million children under the age of five died in 2017, 2.5 million of those within the first month of life, according to the World Health Organization.