This is a summary, written by members of the CITF Secretariat, of:

Healey GR, Golding L, Schick A, Majdoubi A, Lavoie PM, Vallance BA. Gut microbiome and dietary fibre intake strongly associate with IgG function and maturation following SARS-CoV-2 mRNA vaccination. Gut. Dec 2022. DOI: 10.1136/gutjnl-2022-328556

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

In a letter published in Gut, Drs. Genelle Healey, Bruce Vallance and CITF-funded researcher Dr. Pascal Lavoie (University of British Columbia) and their team identified a link between the composition of one’s gut microbiotaThe gut microbiota comprises of all the microorganisms, including bacteria, that live in our gastrointestinal tract. and COVID-19 vaccine-induced immunity. The research suggests that those with higher microbial-derived branched-chain fatty acids (produced via microbial protein fermentation) have more trouble developing a strong immune response with vaccine-induced antibodies effectively binding the virus. On the other hand, those who consume a lot of fiber exhibit a more effective immune response.

Key findings:

  • The composition of the gut microbiota changed after the first dose of Pfizer-BioNTech’s mRNA vaccine in a cohort of health care worker participants: the population of some microorganisms declined and there was a generalized reduction in diversity of the microbiome.
  • The baseline composition of the gut microbiota (i.e., before vaccination) differed between participants showing high and low levels of antibodies following COVID-19 vaccination.
  • The presence of some bacterial species before vaccination seemed to be associated with a reduced ability for vaccine-induced antibodies to bind the virus.
  • Higher levels of microbial-derived branched-chain fatty acids (BCFA) were associated with reduced vaccine responses. BCFA levels are known to be higher in patients with immune-mediated conditions such as inflammatory bowel diseases (but the mechanisms underlying this are not well understood).
  • Participants consuming more fiber showed enhanced vaccine-induced immunity, including stronger antibody responses and binding abilities. Also, high fiber consumers experienced a reduction in BCFAs after vaccination.

Since antibody levels after COVID-19 vaccination have been shown to wane rather rapidly, particularly in vulnerable older populations and among those with other health conditions, the gut microbiome may represent a valuable way to enhance longer-term protection.

This observational study was based on meta-genomic sequencing of stool samples from 52 participants.