New insight into effective triggers of infants’ immature immune response may set scientists on the road toward more effective vaccines that could be administered safely at an earlier age, find medical researchers at Trinity College Dublin in Ireland.

Babies are born with immature immune systems — most scientists believe in order to allow their microbiomes to populate fully with good bacteria and flourish in a way that sets them up for good health. This is why inoculation schedules stretch across the first 13 months of life: babies’ immune systems need time to mature into the ability to mount and encode a reactionary defense.

But that leaves a window of time during which infants are susceptible to preventable infections — especially viral infections like mumps, measles, or rubella, the vaccine (MMR) for which is only administered to children one year old.

Unlike some bacteria, viruses serve no beneficial function in the human body; therefore, scientists suspected newborns’ immune systems might be able to respond more robustly to viral vaccines, if only they could figure out a way to trigger such response safely, without any risk of wiping out their growing collection of good bacteria.

An immune ‘danger trigger’ is known as an adjuvant. It’s one of two main components in any vaccine. An adjuvant instructs the immune system to mount a response to the infection, which in the case of a vaccine is usually a weaker, inactive form, or fragment, of the bacteria or virus. An adjuvant is critical not only for triggering the immune system into action, but also for directing the type of response best suited to fight a particular infection.

“Many adjuvants used in vaccines today were developed in adults. However, babies and children are not simply little adults, and because of this, a child’s immune system responds differently to that of an adult,” explains lead author Dr Kiva Brennan, a research fellow at Trinity’s School of Medicine.

Brennan’s team found a specific class of adjuvants that activate specialised sensors that drive a strong immune response in newborns, despite their immature systems. They’ve published their findings in the highly regarded Journal of Immunology.

“These sensors are normally activated in response to viral infection and direct the immune system to clear viral infections. Harnessing these efficient anti-viral immune responses will help in the design of targeted adjuvants for paediatric vaccines by directly activating immune responses that are fully functional in infants and newborns,” says senior author, Dr Sarah Doyle, an assistant professor of immunology at Trinity.

Infections remain the most common cause of death in early life. The team says the discovery has the potential to allow vaccination — and thus, immunity — at an earlier age, and eliminate the need for multiple booster injections. In other words, the potential to develop shots worth raising a shot to.