The original COVID-19 vaccine trials were designed primarily to assess whether vaccination reduced symptomatic COVID-19 illness. They were not designed to determine whether vaccination prevented infection or transmission before authorisation.
During a European Parliament hearing in October 2022, Pfizer executive Janine Small confirmed that transmission had not been tested before market release. The trial also reported a 95% Relative Risk Reduction (RRR), while the Absolute Risk Reduction (ARR) was approximately 0.84%, illustrating two different ways of presenting efficacy data. These distinctions provide important context when considering the wider discussion surrounding vaccine safety and adverse event reporting.
Since the introduction of the COVID-19 vaccines, much discussion surrounding adverse events has focused on cardiovascular and neurological conditions, yet there is a growing body of published literature examining gastrointestinal (GI) symptoms and disorders following vaccination.
This article aims to summarise the current literature while also highlighting areas of ongoing research and clinical interest.
Digestive symptoms are recognised among the more commonly reported adverse effects following COVID-19 vaccination. Published studies have described:
Nausea
Vomiting
Diarrhoea
Abdominal pain
Dyspepsia (indigestion)
Bloating
Heartburn
Loss of appetite
In most published studies these symptoms developed within hours or days of vaccination and settled without long-term consequences.
Beyond these transient symptoms, peer-reviewed literature has described a number of inflammatory and structural gastrointestinal conditions occurring after vaccination, including:
Enterocolitis
Ischaemic colitis
Microscopic colitis
New-onset ulcerative colitis
Crohn’s disease flares
Diverticulitis
Acute pancreatitis
Autoimmune hepatitis
Gastrointestinal bleeding
Appendicitis
Rare disorders such as Cronkhite–Canada syndrome
Many of these publications are individual case reports or small case series and thus valuable in identifying safety signals that may warrant further investigation through larger epidemiological studies.
Several studies have investigated inflammatory bowel disease (IBD). Isolated flares of Crohn’s disease and ulcerative colitis have been reported following vaccination. Yet mainstream continues to report “Safe and Effective” so as not to cause public confidence to be knocked.
Researchers have proposed several mechanisms that may help explain gastrointestinal symptoms experienced by some individuals. These include:
Immune activation and inflammatory signalling
Endothelial (blood vessel) dysfunction
Mast cell activation and histamine dysregulation
Autoimmune responses
Molecular mimicry
Altered intestinal permeability (”leaky gut”)
Changes in the gut microbiome
Persistence of vaccine-derived spike protein or antigenic material in some individuals
These mechanisms remain areas of active investigation. Some have stronger supporting evidence than others, and none should currently be regarded as explaining every case of post-vaccination illness.
Anyone experiencing persistent or severe gastrointestinal symptoms should first seek an appropriate medical assessment. Blood in the stool, persistent vomiting, severe abdominal pain, dehydration, fever, unexplained weight loss or abnormal blood tests warrant prompt investigation. Conditions such as infection, food poisoning, medication-induced enteritis, inflammatory bowel disease, gallbladder disease, pancreatitis, coeliac disease and Clostridioides difficile infection should be excluded where appropriate.
Alongside conventional investigation and treatment, a number of clinicians and organisations have proposed supportive approaches for individuals who believe they are experiencing persistent symptoms following COVID-19 vaccination or long COVID. These should be viewed as areas of ongoing research and clinical observation rather than universally accepted treatment protocols.
General supportive measures frequently discussed include:
Maintaining good hydration and electrolyte balance.
Eating a minimally processed, nutrient-dense diet.
Temporarily avoiding foods that appear to aggravate symptoms.
Supporting recovery of the gut microbiome, particularly following antibiotic use.
Reviewing medications that may contribute to gastrointestinal irritation.
Considering appropriate blood tests and stool investigations where indicated.
Some individuals also choose to investigate whether specific foods contribute to ongoing gastrointestinal symptoms. Food intolerances may become more noticeable following periods of gut inflammation, infection or disruption of the gut microbiome. Working with a suitably qualified practitioner, some people find structured elimination diets, careful food diaries or selected food intolerance testing helpful in identifying foods that may exacerbate symptoms. Commonly reported triggers include dairy, gluten-containing grains, eggs, soy, alcohol, caffeine, artificial sweeteners, high-histamine foods and fermentable carbohydrates (FODMAPs). While commercially available food intolerance tests vary considerably in their evidence base, carefully supervised elimination and reintroduction remain widely recognised methods of assessing individual food triggers.
Dr Peter McCullough and colleagues have published and discussed a proposed “base spike detoxification” protocol using nattokinase, bromelain and curcumin. The rationale is that these compounds may theoretically assist with reducing inflammation, supporting fibrinolysis and promoting clearance of spike protein. This remains a proposed therapeutic approach rather than an established standard of care.
The World Council for Health has similarly published educational guidance discussing nutritional support, anti-inflammatory diets and supplements including nattokinase, bromelain, curcumin, quercetin, vitamin C and other nutrients as possible supportive measures for those wishing to explore this area further.
Dr Tina Peers has worked extensively with patients experiencing long COVID and post-vaccination illness. Her work explores mast cell activation, histamine intolerance, immune dysregulation and oxidative stress as possible contributors to persistent symptoms.
She has also discussed the potential role of augmented N-acetylcysteine (Augmented NAC) as part of a broader strategy to support glutathione production, antioxidant defences and detoxification pathways. Whilst conventional NAC has a long-established role within medicine, augmented formulations and their specific role in post-vaccination illness remain emerging areas of clinical practice.
Another practitioner whose work may be of interest is Lucy De Angeles, a naturopath and nutritional therapist. She focuses on restoring cellular health through hydration, bowel function, liver support and improving absorption of essential nutrients.
Particular emphasis is placed on:
highly bioavailable omega-3 essential fatty acids
hydration
bowel regularity
liver support
mineral balance
reducing inflammatory foods
identifying individual food intolerances
supporting digestive function before introducing more complex interventions
Her work reflects a holistic nutritional model designed to optimise the body’s natural healing capacity.
Dr Clare Craig has published (two books: “Expired” and “Spiked” fully researched and evidenced material on both the lockdown era and the vaccine issues) and spoken extensively about vaccine safety, pharmacovigilance, excess mortality data and the interpretation of adverse event reporting systems. Her work encourages careful examination of published data and continued transparency when evaluating both benefits and risks associated with medical interventions.
Some researchers and clinicians have proposed further hypotheses involving nicotinic acetylcholine receptors, cholinergic signalling and their potential role in COVID-19 and post-vaccination illness.
Dr Bryan Ardis has discussed hypotheses involving venom-like mechanisms together with possible roles for nicotine and nicotinic receptors. These ideas have generated considerable discussion and continue to be explored by clinicians. Readers wishing to investigate this area are encouraged to examine the original presentations alongside the available scientific literature and draw their own conclusions.
As with many developing areas of science, continued research will determine which hypotheses become more strongly supported and which require revision as additional evidence emerges.
The published literature demonstrates that gastrointestinal symptoms following COVID-19 vaccination have been reported across a broad spectrum ranging from transient digestive upset to rare inflammatory gastrointestinal conditions. Whilst many reported events remain uncommon, continued pharmacovigilance, open scientific enquiry and ongoing research remain essential.
This article has focused specifically on gastrointestinal health. Readers interested in broader areas of post-COVID-19 vaccination research may also wish to explore the work of Professor Angus Dalgleish, an oncologist and immunologist who has written and spoken about possible links between immune dysregulation, persistent spike protein, and cancer progression in some patients. These observations remain in ongoing research and scientific debate, and readers may wish to consult Professor Dalgleish's published papers, presentations and interviews alongside the wider scientific literature.
Medical investigation does not take place in a vacuum. The NHS works within financial, staffing and time constraints, influencing waiting times, access to investigations and the range of treatments available. Some clinicians, including Dr Sarah Myhill and other retired or independent doctors, argue that modern healthcare has become increasingly protocol-driven, with standardised pathways taking precedence over more individualised clinical investigation.
Whatever one’s perspective, patients experiencing persistent or unexplained symptoms should feel empowered to ask questions, seek appropriate investigations, request second opinions (whilst listening to their bodies) where appropriate and work collaboratively with healthcare professionals. Medicine evolves, and important advances often come from remaining curious and willing to re-examine existing assumptions in the light of new evidence.
Most vaccinations (for people and animals) when examined historically rarely and truly demonstrate the disappearance of disease, rather it was diminishing at the point of vaccination. An interesting part of scientific history that rarely comes to light until researched more deeply. There is much more on this topic that may sound initially controversial but many off-mainstream books examine these scenarios.
Keeping an open mind is so important as financial incentives have been inextricably linked for decades, with the ARR (absolute risk reduction) rarely mentioned - only the much marketed RRR (relative risk reduction).
Many ongoing scientific enquiries may not either be done, or even become public for many years as there is considerable financial disincentive. It is up to us to become our own medical ambassadors, armed with as much research both off and on mainstream and listen to our bodies to ascertain what is right for our bodies.
This article was developed from my own questions and areas of interest, together with research collated using ChatGPT to help bring together published literature and other publicly available resources into a format that is easier to read and more accessible. Every effort has been made to reference relevant sources wherever possible.
Medicine and science continue to evolve, as is understanding of COVID-19 (related to all coronaviruses); vaccination and associated health conditions is developing. This article is not designed to be definitive nor complete but to encourage readers to explore literature for themselves, consider a range of perspectives, ask questions and discuss any health concerns with healthcare professionals.
We are all responsible for making informed decisions about our health. Listen to your body, remain open to new evidence, and continue learning. If any factual inaccuracies, omissions or newer evidence are identified, please notify the author who is happy to acknowledge and update this article accordingly in the interests of accuracy, transparency and ongoing scientific enquiry.
Lee DS, et al. Significance of Digestive Symptoms After COVID-19 Vaccination: A Retrospective Single-Center Study. American Journal of Emergency Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC9144838/
Ajmera K, et al. Gastrointestinal Complications of COVID-19 Vaccines. https://pmc.ncbi.nlm.nih.gov/articles/PMC9097558/
Ischaemic Colitis Following COVID-19 Vaccination (case report). https://pmc.ncbi.nlm.nih.gov/articles/PMC9100719/
Massad M, et al. Association Between COVID-19 Vaccination and Gastrointestinal Side Effects. https://pmc.ncbi.nlm.nih.gov/articles/PMC12434069/
Inflammatory Bowel Disease Activity Following COVID-19 Vaccination. https://pmc.ncbi.nlm.nih.gov/articles/PMC10781543/
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Cronkhite–Canada Syndrome Following mRNA COVID-19 Vaccination. https://www.e-ce.org/journal/view.php?number=7871
Immune Profiling Demonstrates a Distinct Response in Patients with Post-Acute Sequelae After SARS-CoV-2 Infection Compared with Vaccination. https://pmc.ncbi.nlm.nih.gov/articles/PMC8598962/
Hulscher N, et al. Clinical Approach to Post-acute Sequelae After COVID-19 Infection and Vaccination. https://pmc.ncbi.nlm.nih.gov/articles/PMC10663976/
Halma MTJ, et al. Strategies for the Management of Spike Protein-Related Pathology. https://www.mdpi.com/2076-2607/11/5/1308
World Council for Health. Spike Protein Detox Guide. https://www.worldcouncilforhealth.org/wchresources/spike-protein-detox-guide/
Amrita Nutrition. Understanding Augmented NAC. https://www.amritanutrition.co.uk/blogs/news/understanding-augmented-nac
Oliveira ASF, et al. The SARS-CoV-2 Spike Protein May Interact with Nicotinic Acetylcholine Receptors. https://pmc.ncbi.nlm.nih.gov/articles/PMC7386492/
O’Brien BCV, et al. SARS-CoV-2 Spike Ectodomain Targets α7 Nicotinic Acetylcholine Receptors. https://www.jbc.org/article/S0021-9258(23)01735-0/fulltext
Skok M. The Role of α7 Nicotinic Acetylcholine Receptors in Post-COVID Conditions. https://www.sciencedirect.com/science/article/abs/pii/S1357272524000104
Lucy De Angeles. Natural Born Healer. https://www.naturalbornhealer.co.uk/
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