Infectious disease accounts for more than one-third of infant deaths worldwide, according to the World Health Organization. No such vaccine exists because scientists haven’t understood why infants rapidly lose immunities.

Babies repeatedly become ill because their immune system is extremely forgetful, researchers have discovered. Published in the Journal of Immunology in May, the discovery suggests a new angle immunizations could take to better protect infants and children from infectious diseases. Immunizations protect people by 'teaching' immune systems to remember pathogens.

'The perfect vaccine would be a single dose given at birth that generates long-lasting immunity, but no such vaccine exists ' said immunologist Brian Rudd at the College of Veterinary Medicine, the study’s lead author.

'Our finding could change the way we immunize infants and ultimately lead to more effective ways of enhancing immunity in early life,' said Rudd.

Immunity against most microbes depends on forming memory T cells that remember specific pathogens and can rapidly respond to future infections. Adults almost always generate large numbers of effective memory T cells during infection, around 10 percent of which stay in a long-lived memory pool to rapidly respond next time.

Rudd found that newborn T cells generated in response to infection in mice made T cells that responded more rapidly to infection than adult cells, but die off sooner, before they can give rise to memory T cells and remember what they’ve learned.

The team now hope to find a way to change the behaviour.

'We hope to find a way to make neonatal cells behave more like adult cells in how they learn from vaccines and respond to infection,' said Rudd.

'Knowledge gained from these studies could be used to design more effective therapeutic interventions and vaccines that can be safely administered in early life.'