A new study has revealed that the gut microbiome, the community of bacteria that live in our digestive tract, can influence how well people respond to mRNA COVID vaccines. The study, published in the journal npj Biofilms and Microbiomes, involved 68 people with HIV and 75 healthy individuals who received either the CoronaVac (Sinovac) or the BNT162b2 (BioNTech) vaccine.
Gut microbiome and immune response
The researchers performed shotgun metagenomic sequencing, a technique that analyzes the DNA of all the microbes in a sample, on stool samples collected from the participants before and one month after the second dose of vaccination. They also measured the levels of antibodies and immune cells that target the spike protein of the coronavirus, which is the main component of both vaccines.
They found that a less diverse gut microbiome was associated with a stronger vaccine response, marked by higher levels of spike protein antibodies and spike specific CD4 T-cells. These are key components of the immune system that help to neutralize the virus and prevent severe infection.
The researchers also identified specific bacteria that were associated with different vaccine responses. For example, Bifidobacterium adolescentis was persistently higher in subjects with high neutralising antibodies to CoronaVac vaccine, while Roseburia faecis was positively correlated with neutralising antibodies in BNT162b2 vaccinees.
Gut microbiome and adverse events
The study also examined the relationship between the gut microbiome and adverse events following vaccination, such as fever, headache, fatigue, and pain at the injection site. The researchers found that some bacteria were enriched in individuals who experienced fewer adverse events, such as Prevotella copri and two Megamonas species. These bacteria may play an anti-inflammatory role in host immune response, according to the researchers.
Implications and limitations
The study suggests that modulating the gut microbiome may be a potential strategy to enhance vaccine efficacy and reduce adverse events. The researchers propose that oral supplementation of prebiotics or probiotics, which are substances or microorganisms that can alter the gut microbiome composition, may be beneficial for vaccine recipients.
However, the study also has some limitations, such as the small sample size, the lack of a placebo group, and the heterogeneity of the participants in terms of age, sex, health status, and diet. Therefore, more studies are needed to confirm and generalize these findings to larger and more diverse populations.