Cancer patients who had been stable for years suffered aggressive relapses shortly after receiving Covid-19 booster jabs, MPs have been told in stark testimony that has prompted calls for urgent regulatory scrutiny.
Specialist’s Claims to MPs
Professor Angus Dalgleish, a leading skin cancer specialist and former foundation chair of oncology at St George’s, University of London, issued the warning to the All-Party Parliamentary Group (APPG) on Pandemic Response and Recovery. He stated that six of his own long-term stable stage-4 melanoma patients all relapsed within weeks of a Covid booster in late 2021 and early 2022, a pattern he claims is supported by emerging international research.
“The only common factor we could find was the booster. These patients had been stable for three to 18 years. The relapses required new treatment,” Professor Dalgleish told the group. He emphasised that the concern applied to the booster or third dose onwards, not the initial two-dose regimen. His claims were described by APPG co-chair Esther McVey MP as “among the most alarming” the group had heard.
The Proposed Immune System Mechanism
Central to Professor Dalgleish’s testimony is a proposed biological mechanism where the vaccine impacts the body’s cancer surveillance. He told MPs that laboratory testing showed the booster dose induced “profound T-cell exhaustion and suppression”. T-cells are a critical component of the immune system responsible for identifying and destroying cancerous cells. When these cells become ‘exhausted’, their function is weakened, potentially diminishing the body’s natural ability to keep existing cancers in check.
Professor Dalgleish, who is also Principal of the Institute for Cancer Vaccines and Immunotherapy, posits that the vaccines suppress the innate and T-cell systems, disturbing this surveillance. He also raised concerns about potential genetic effects, suggesting the mRNA might insert itself into human DNA at random points, potentially switching on cancer-causing genes or turning off natural anti-tumour defences.
This testimony was reinforced by reports from other clinicians, such as colorectal surgeon James Royle, who described a dramatic shift towards younger patients presenting with late-stage, aggressive cancers, alongside increased clotting and inflammation—conditions known to contribute to cancer spread.
Graham Stringer MP, the APPG’s co-chair, highlighted a key regulatory gap, noting that standard carcinogenicity or genotoxicity studies were not conducted for the Pfizer mRNA vaccine before its emergency authorisation in December 2020.
Regulatory and Scientific Responses
The Medicines and Healthcare products Regulatory Agency (MHRA) has responded to the concerns, stating the current evidence does not support a link. Dr Alison Cave, MHRA Chief Safety Officer, said: “Given the prevalence of cancer in the UK population and the vast numbers of people who have received COVID-19 vaccines, the numbers of reports of cancer reported to MHRA in association with the COVID vaccines are very small.”
She pointed to peer-reviewed, population-level studies conducted in the UK, France, Denmark, Finland, Iceland, Norway and Sweden, involving millions of people, which found no evidence of increased cancer rates. The MHRA, along with other international regulators, maintains there is no established causal link and that safety monitoring is continuous.
Pfizer has stated there are no signs of DNA mutation or vaccine-induced cancer reported for its COVID-19 vaccine, asserting that residual DNA is within permitted limits and components are not expected to have carcinogenic potential. The European Medicines Agency has similarly stated such studies were not performed as genotoxic potential was not expected.
The broader scientific consensus, echoed by bodies like the National Cancer Institute, is that there is no information suggesting COVID-19 vaccines cause cancer or recurrence. Studies on cancer patients have shown vaccines are generally safe and effective, offering protection against severe COVID-19, though immunity may wane faster than in the general population.
Conflicting Research Landscape
Amid this official position, some studies have reported associations warranting further investigation. Professor Dalgleish cited international research including a major Spanish hospital study and population data from South Korea and northern Italy. A 2025 South Korean study of over 8.4 million individuals reported statistically significant associations between vaccination and increased risk of certain cancers one year later, though the authors described this as an association, not causation, and other experts suggest the findings may reflect increased detection.
An Italian population study in Pescara reported a 23% higher risk of cancer diagnosis within 180 days of a first dose, with specific increases for breast and bladder cancer. Another study in Italy’s Reggio Emilia province found vaccination associated with a higher risk of hospitalisation for certain cancers. A review in *Oncotarget* of 69 publications noted reports of malignancies in temporal association with vaccination but underscored the need for more rigorous study.
Conversely, research presented at ESMO 2025 suggested mRNA COVID vaccines given near the start of immunotherapy might improve survival odds in cancer patients, indicating a potential complex role in immune reprogramming.
Professor Dalgleish concluded his testimony with a direct appeal, telling MPs: “In my opinion, this is no longer a hypothesis. The data are in. The mechanisms are understood. The signal is screaming. It is time to act.” The APPG session is expected to intensify calls for further independent investigation into the long-term safety profile of the mRNA COVID-19 vaccines.