A study has shown that vaccinating newborn babies might be possible.
Agents could be added to vaccines to boost the immune response
Currently, most immunisations are given to babies at two months of age because they are unable to mount an immune response to the majority of vaccines.
But US scientists have found a way to stimulate an immune response in newborns, following the discovery of a type of molecule present at birth.
The team, writing in the journal Blood, say infant mortality could be reduced if babies are vaccinated at birth.
Newborn babies have an immature immune system. This, coupled with their reduced response to most vaccines, leaves very young babies vulnerable to infections.
But immunologists from the Children's Hospital, Boston, say they have found a molecule, called Toll-like receptor 8, which could be stimulated to boost immune responses and enable vaccination.
Toll-like receptors, or TLRs, are found on the surface of certain types of white blood cells, and are the first line of defence against infection.
They detect the presence of invading bacteria and viruses, and trigger the production of cytokines, a type of protein, that cause other immune cells to mount a defence against infection.
Babies, like adults, have 10 kinds of TLRs, but unlike in adults, most, when stimulated, do not trigger this kind of immune response.
This, according to the researchers, could be an evolutionary factor, whereby a baby's immune system is inactivated during pregnancy so as to prevent attacking its mother's.
However, the researchers discovered that one of the TLRs, TLR-8, was an exception and could be stimulated by several compounds to produce an immune response.
Dr Ofer Levy, lead researcher on the study and an immunologist from Harvard Medical School, said: "These are exactly the kinds of responses you need to get good vaccine responses."
These compounds could perhaps given to babies alongside vaccines, he said, to boost the neonatal vaccine response, thereby enabling vaccination of newborns.
"We believe we have stumbled across the molecular holy grail of neonatal immunology."
His team will now carry out further studies to test this possibility in animals and eventually in babies.
He said his findings could have real practical benefits.
"In the Western world we tend to vaccinate babies at two, four and six months - this means that we leave a window of susceptibility," said Dr Levy.
"If we could come up with a way to get the system to work at birth, then you would close that window of susceptibility."
From a global health perspective, he said, there is evidence that babies in the developing world have the highest rate of contact with the healthcare system at birth, compared to the rest of their childhoods.
"And if a vaccine could be given at birth, you will achieve better vaccine coverage rates," he said.
But Adam Finn, professor of paediatrics from Bristol University, said it was too early to say whether this research could change vaccination.
"This is an interesting observation about one aspect of a baby's immune system that appears to work quite well and which could, theoretically, be exploited to make vaccines more effective in the future," said Professor Finn.
"But it is important to remember that it is a preliminary observation."