A one-shot jab to protect newborns against meningitis and other fatal infections has been developed by scientists.
The vaccine has proved effective in monkeys, the final animal model before human trials, after a substance or 'adjuvant' was added to boost their immune response.
Newborns are highly vulnerable to infections and don't respond well to vaccines because their young immune systems mount weak antibody responses.
So immunising them before they are two months old, the current limit for most, would prevent thousands of child deaths a year.
Dr Ofer Levy, a paediatric infectious disease specialist at Boston Children's Hospital, Massachusetts, said: "Our efforts to understand the biology of the newborn immune system has now led to adjuvant approaches that may enable earlier protection of newborns and young infants from life threatening infectious diseases, such as pneumococcus, pertussis or even respiratory syncytial virus (RSV)."
Pneumococcus is the most common cause of bloodstream infections, pneumonia, meningitis and ear infections in young children.
Pertussis, also known as whooping cough, is also highly contagious while the cold like symptoms of RSV can be serious in very young babies.
A 5-in-1 single jab already protects against diphtheria, tetanus, whooping cough (pertussis), polio and Hib, a bacterial infection that can cause severe pneumonia or meningitis in young children.
But it isn't recommended by the NHS until babies are eight weeks old.
Globally, vaccines that could be given at birth could sharply reduce infant mortality. Currently, the only vaccines that work in newborns are those for tuberculosis, polio and hepatitis B, with the latter two requiring multiple doses.
Now two new studies cap a decade of research in Dr Levy's lab aimed at tailoring vaccines unique to newborns' immune systems.
Pneumococcal vaccine was used as a test case because it can cause potentially fatal pneumonia, meningitis, and sepsis, or blood poisoning, in infants.
In the first published in the Journal of Clinical Investigation-Insight newborn Rhesus monkeys were given a series of three shots with the existing vaccine known as Prevnar 13.
This is already packaged with an adjuvant (Alum), but half the monkeys who also received another called 3M-052 were much quicker to develop an antibody response after 28 days, even before a second dose.
Pneumonia resistance improved
And their antibody levels were 10 to 100 times greater than that with Prevnar 13 alone - high enough to ensure protection against infection. Immune cells that specifically fight pneumonia were also dramatically enhanced.
Dr Levy said: "The protective antibody response we saw was so strong that it's conceivable that you could get protection with one shot.
"This is critical because in many parts of the world, birth is the most reliable point of healthcare contact. After birth, it becomes challenging to bring children in for repeated clinic visits."
The adjuvant 3M-O52 works by stimulating the chemicals of white blood cells that fight infection.
Studying white blood cells from newborns' umbilical cords, the researchers also saw the number of immune cells increased when given 3M-052 alone. When it was added to Prevnar 13, this improved even more.
The added substance is designed to minimise side effects, being made with chemicals that mix poorly with water. This keeps it from getting into the bloodstream, where it could cause inflammation and flu like symptoms.
Fevers and chills
Explained Dr Levy: "Rather than floating all over the place causing fever and chills, when you inject this 3M-052 adjuvant, it stays put in the muscle and enhances the immune response to the vaccine."
His second study published in the Journal of Allergy and Clinical Immunology used a different adjuvant called CLO75 to both maximize immune response and avoid inflammation.
It was specially engineered to be taken up by infectious cells which trigger immune cells to make antibodies.
When added to human cells in a dish and when injected into mice, it stimulated immune responses that were as good or better than those induced by the tuberculosis jab, one of the few that work in newborns.
The team's next steps are to develop a highly stable formulation, obtain more safety data and further investigate age specific responses, comparing newborns with older infants.
Dr Levy plans to work with scientists from around the world, via the Precision Vaccines Program he founded last year, to work towards eventual human trials.
He added: "There's not a long list of vaccines that can be given at birth and we need better vaccine formulations against a range of early life infectious pathogens. We hope to meet these challenges."