Babies treated with antibiotics respond less to vaccines

A new study from Australia has found that babies treated with antibiotics as newborns have reduced immune responses to vaccines given later in infancy. They speculate that changes to the “microbiome” - the community of bacteria that live on each of us - underpin the effect. The findings have been published in Nature, and Claire Waddington - a senior clinical lecturer in infectious diseases at Liverpool School of Tropical Medicine - has been taking a look at them for us…

Claire - What this paper set out to look at was whether antibiotic exposure in early life could affect response to vaccines in young infants and essentially their bottom line was that it did indeed seem that infants given antibiotics when they were very young had different responses to vaccines subsequently.

Chris - They didn't respond as well, they were less well protected?

Claire - This study looked at the immune markers of what we think predicts how well the vaccines are going to work. They weren't able in this paper to drill down specifically to show that it had a negative impact. But what they did show was that the immune response looked less optimal in those infants that were given antibiotics in early life.

Chris - And just to be clear, these are vaccines for all sorts of infections, both bacteria and viruses. It wasn't just your ability to protect someone with vaccines against a bacterial infection and how that was affected by antibiotics, it was everything?

Claire - They did look at a range of different vaccines and these were the standard vaccines that you would give to most infants in most parts of the world. And some of those vaccines are targeting viruses like rotavirus and some of them are targeting bacterial infections like streptococcus pneumoniae. And they did find that the immune response and the impact of antibiotics on that immune response was different looking across the board at all of the vaccines that infants get.

Chris - And was there a window when exposure to antibiotics within that window is most likely to produce this effect? It must wear off at some point.

Claire - They looked at antibiotic exposure in infants through a variety of different routes. One of the groups they looked at was when mums get antibiotics in the late stage of pregnancy. And they also looked at infants given antibiotics in the early few hours or days of life. And then they also looked at infants that were exposed after they'd been born, but through their mum's breast milk.
The strongest effect with the infants that were given individually antibiotics in that early neonatal period, they were able to see that even if mums had antibiotics in the latter part of pregnancy, they could detect a difference in the infant's microbiome, so the bugs that make up the infant's gut. But because they were following these infants prospectively, they were able to show that that effect wore off by seven weeks of life. Whereas those infants that had antibiotics themselves still clearly had a difference in their microbiome at seven weeks.

Chris - And what do they propose is the mechanism by which you get this sort of legacy effect of early life exposure to antibiotics that then affects how you immunologically respond to vaccines later?

Claire - The suggestion in this paper is that the effect that we see on vaccine responses is probably mediated through the microbiome. It looks like early antibiotic exposure, particularly at the higher doses that we see in infants that get it themselves, seems to change the microbiome and that change in the microbiome is probably affecting the response to vaccines.

Chris - Does it go back to normal later though?

Claire - We don't have the direct data to show that at five years, they have different responses. And even in this study, what it was largely looking at was associations in the infants themselves. But what we do know overall is that very early neonatal period and early infancy is really important for subsequent health.

And that first 1000 days of life, as it's often termed, is absolutely crucial to health in the rest of your life. Vaccine responses are part of that equation.

Chris - What do you think, then, are the important questions we now need to answer? Or what should we consider changing? We don't want to make knee-jerk changes to any kind of protocols and policies and people don't get antibiotics for no reason, hopefully. But what should go through our minds then off the back of this and make us think differently?

Claire - I think one of the important strengths of this study and conclusions from this study is that there is something we could potentially do about this. And that namely is looking at the effect of probiotics in those infants that are at risk of having this muted response to vaccines. So those infants that require antibiotics for whatever reason.
There is probiotics that we already quite commonly use in neonates and newborns. And that gives us a potential real world solution to this. And if we can show that giving these probiotics is able to restore microbiome in these infants and that lets them get the best possible chance of a good immune response to vaccines, then that could have a significant impact in terms of all of life health as we were talking about.