Vaginal birth lays the foundation for a healthy microbiome for newborns. This in turn is important for the immune system. A study now shows that the type of birth and the associated bacterial colonization in the intestine also influence how well the children later respond to vaccinations. According to this, more antibodies against pneumococci and meningococci can be detected in babies born vaginally after the corresponding vaccinations than in peers who were born by caesarean section. The results could help to develop special programs for caesarean babies that promote the development of a healthy intestinal flora and a strong immune system.
On their way through the birth canal, newborns receive numerous helpful bacteria from their mother, which lay the basis for the children's microbiome. In the further course of life, the composition of the bacterial intestinal dwellers is influenced by many other factors: Does the baby receive breast milk or formula? Does it need to be treated with antibiotics? And in what environment does it grow up? All of this determines which bacteria are present in the child's intestines and how strongly. The bacterial community, in turn, helps shape the immune system.
Vaginal or caesarean?
A research team led by Emma de Koff from the University Hospital Utrecht in the Netherlands has now investigated to what extent the method of birth and the microbiome influence how well children respond to vaccinations. To do this, they took stool samples from 120 newborns, who were born either vaginally or by caesarean section, at different times, which they used to examine the intestinal microbiome. Using saliva samples after twelve and 18 months, they also determined how many antibodies the children had formed in response to two early childhood vaccinations: the pneumococcal vaccination, in which, according to the Dutch vaccination recommendation, the first dose was given at the age of two months and the last at the age of eleven months and the meningococcal vaccine given to the children at 14 months of age.
The result: "Vaginal birth is associated with higher antibody levels in response to the two vaccinations," the authors report. The stronger immune reaction is apparently mediated by the bacterial colonization in the first few weeks of life: one week after birth, children born vaginally had significantly more bifidobacteria and Escherichia coli in their intestines than children who were born by caesarean section. Although the intestinal flora adjusted over time, so that at the age of two months - at the time of the first vaccination - there were hardly any differences between the intestinal flora in vaginally born and caesarean children, the researchers found a statistically significant connection between the bacterial colonization in the first week after birth and later response to vaccinations.
Bacterial flora shapes the immune system
"The first few weeks of life represent a critical time window in which the microbiome in the intestine shapes the maturation of the immune system," the researchers explain. If the microbiome is unfavorable at this time due to a caesarean birth, this can affect the immune response to vaccinations months later. De Koff and her colleagues identified breastfeeding as a further influencing factor: for example, children born vaginally who were breastfed in the first few months of life had 3.5 times higher antibody levels than their peers who were bottle-fed.
The researchers found no significant effects for other possible influencing factors, including administration of antibiotics, pets and siblings. However, the number of cases examined was relatively small: of the original 120 infants, 101 took part in the follow-up examination at twelve months and 66 at the follow-up examination at 18 months. The extent to which the different antibody levels in the saliva indicate that caesarean children may be less well protected against the relevant diseases cannot be derived from the current study.
Support the microbiome early on
"I don't think that a change in the vaccines themselves will be the consequence of this study," comments infectiologist Maria Vehreschild from the University Hospital Frankfurt, who was not involved in the study. "Rather, I see potential here for the development of microbiota-based therapies that can be given in the phase of immune maturation of the newborn in order to later achieve an optimal vaccination result." The pediatrician Michael Zemlin from the Saarland University Hospital in Homburg agrees : "After all, it's not just about the vaccination response, but about the immune response against all possible pathogens that we encounter in life," he comments.
Source: Emma de Koff (Wilhelmina Children's Hospital and University Medical Center Utrecht, The Netherlands) et al., Nature Communications, doi: 10.1038/s41467-022-34155-2