Rotavirus diarrhoea is a major cause of infant and child mortality, especially in India. However, like most other oral vaccines, oral rotavirus vaccines have lower efficacy and immunogenicity when given to children in developing countries, compared to those in developed countries.
Furthermore, the intestinal microbiota — which could be vital to the adaptive immune response to live oral vaccination — may be compromised in children in developing countries due to widespread faecal contamination, pathogen infection, frequent antibiotic intake, or malnutrition.
These factors are thought to affect oral vaccine immunogenicity, and probiotics could positively alter the intestinal microbiota and improve immune response to oral vaccines.
In addition, zinc deficiency is pervasive among Indian children, thereby affecting adaptive immune system function.
Based on this, an RCT led by researchers from the Christian Medical College in Vellore, India was conducted to determine the effect of probiotic and zinc supplementation on infants' immune response to Rotarix.
The researchers enrolled 620 infants aged between five and six weeks — each weighing at least 3.2kg — in the study, dividing them into four groups: one supplemented with zinc and a probiotic (1010 Lactobacillus rhamnosus GG), one given a probiotic supplement and zinc placebo, one given a probiotic placebo and zinc supplement, and the last given probiotic and zinc placebos.
They were administered Rotarix at six and 10 weeks of age and given their respective supplements and placebos. They were also administered the trivalent oral poliovirus vaccine (OPV) at birth and six, 10 and 14 weeks of age.
The researchers then observed "modest improvement" in the immunogenicity of Rotarix among those who had received probiotic supplementation.
They said that even small improvements in immunogenicity to oral rotavirus vaccines "may translate into higher efficacy", which could have an effect on vaccine impact in countries with a high disease burden.
The infants who had received zinc but not probiotic supplementation, on the other hand, showed no improvement whatsoever:"Provision of zinc alone did not improve rotavirus vaccine immunogenicity, and there was no significant interaction between zinc and probiotics in their association with seroconversion."
It added that probiotic supplementation did not alter the diversity or broader composition of the infants' bacterial microbiota.
The researchers concluded: "(The) modest effect of combined supplementation deserves further investigation."
"The effect of probiotics and zinc supplementation on the immune response to oral rotavirus vaccine: A randomized, factorial design, placebo-controlled study among Indian infants"
Authors: Robin P. Lazarus, et al.