Can your gut microbiota predict the effectiveness of the Covid vaccine?

Tell me what your microbiota looks like, and I’ll tell you how the Covid vaccine protects you. 

That’s the takeaway from a study ¹ published last September in the academic journal Signal Transduction and Targeted Therapy.

The researchers succeeded in demonstrating that the presence of certain bacteria and molecules in the gut prior to the first injection may reinforce the immunity conferred by the vaccine, thereby extending its duration of action. 

A promising avenue for the development of new adjuvants.

• 161 participants
• two Covid-19 vaccines
• six months follow-up

This finding was made thanks to the participation of 161 volunteers enrolled for six months. 

121 participants received two injections of Comirnaty, Pfizer-BioNTech’s mRNA vaccine, while the remaining 40 received CoronaVac, Chinese firm Sinovac Biotech’s inactivated virus vaccine. No volunteers were infected with Covid during the study. Immediately prior to vaccination, then one month and six months later, the researchers took the following samples from the participants:

• blood samples to measure antibody concentrations; 
• stool samples to identify the bacteria in their gut microbiota and measure the levels of substances produced by the subject and their bacteria (vitamin B3, GABA, fumaric acid, etc. – i.e., the renowned “metabolome”).

The researchers found, first of all, that Comirnaty achieves better immunity than CoronaVac. 

State of gut flora modulates vaccine-induced immune response

In the Comirnaty group, patients whose gut microbiota before the first injection was abundant in bacteria such as Bacterium adolescentis, Bifidobacterium (sidenote: Bifidobacterium A genus of Y-shaped bacteria, most species of which are beneficial to humans. They are found in the gut of humans, and in some yogurts.

They:
- Protect the gut barrier 
- Participate in the development of the immune system and help fight inflammation 
- Promote digestion and improve symptoms of gastrointestinal disorders Sung V, D'Amico F, Cabana MD, et al. Lactobacillus reuteri to Treat Infant Colic: A Meta-analysis. Pediatrics. 2018 Jan;141(1):e20171811.  O'Callaghan A, van Sinderen D. Bifidobacteria and Their Role as Members of the Human Gut Microbiota. Front Microbiol. 2016 Jun 15;7:925. Ruiz L, Delgado S, Ruas-Madiedo P, et al. Bifidobacteria and Their Molecular Communication with the Immune System. Front Microbiol. 2017 Dec 4;8:2345. ) bifidum and Roseburia faecis had higher levels of SARS-CoV-2 antibodies in their blood six months later. The same type of stronger, longer-lasting immunity was found in those with a metabolome richer in vitamin B3 and GABA.

In the CoronaVac group, a low abundance of Faecalibacterium prausnitzii and a higher abundance of Phocaeicola dorei – a signature found in Covid-infected patients – was associated with better immunity at six months, as was a higher presence of fumaric acid in the metabolome, a compound known to hinder virus replication.

Another finding was that, for the Comirnaty group, a greater proportion of the bacterial strains in the microbiota altered by the vaccine had not recovered their pre-vaccination state when compared with the CoronaVac group. While it remains difficult to analyze the consequences, the researchers point out that some of the strains affected are the same as those found altered in people suffering from long Covid.