According to a study published in the journal Communications Biology, gut bacteria that break down a sugar known as "fucose" can compromise the immune response to the COVID mRNA vaccine. The researchers from the Okinawa Institute of Science and Technology (OIST), Japan, explained the impact of the gut microbiome on overall immune health and its role in the varied degree of effectiveness of vaccination observed in the general population.

In the study, researchers took a stool sample and multiple blood samples from 96 healthy participants, starting before the first dose of the vaccine and ending a month after the second dose. They analyzed the genes from immune cells in the blood and bacteria in the gut to evaluate if there was any association between the gut microbiome and T-cell and antibody levels.

The findings of the study revealed that increased "fucose" digestion by bacteria in the gut before vaccination was associated with lower numbers of T-cells activated by vaccination. They observed that individuals who had a lower T-cell response had a gut microbiome with high activity in fucose digestion.

Additionally, they also found that individuals with a reduced T-cell response had higher expression of two genes, FOS and ATF3, before the vaccination. Individuals with increased expression of FOS and ATF3 before vaccination had microbiomes with high activity of fucose digestion, indicating that the guts influence on the immune system happens through a route including FOS and ATF3.

(Source: https://health.economictimes.indiatimes.com/news/diagnostics/gut-bacteria-suppresses-immune-responses-to-covid-19-vaccine-research/99645030 )