Doctors have successfully used vaccination to treat a patient with COVID-19 in what is thought to be the first instance of the vaccine being used for therapy instead of prevention.

Ian Lester, 37, a dispensing optician from Pontypridd who has a rare genetic immunodeficiency, tested positive for COVID-19 for seven-and-a-half months after catching the virus.

The virus was finally cleared from his body after clinicians from the Immunodeficiency Centre for Wales used two doses of the Pfizer vaccine to treat him and scientists from Cardiff University monitored his immune system’s response.

It suggests the vaccine successfully kick-started Mr Lester’s immune system to clear the virus – and it is now hoped this approach could be used to treat other patients who are immune compromised.

“They went above and beyond for me. I will be forever thankful to the doctors, nurses and scientists who helped me,” said Mr Lester, whose case is outlined in the Journal of Clinical Immunology.

Mr Lester has Wiskott-Aldrich Syndrome, a rare condition which causes immunodeficiency, so he has a dampened response to infection. When he caught COVID-19 in December 2020, Mr Lester was unable to fight off the virus and it was repeatedly detected for at least 218 days. This is different to long COVID where the effects of infection may remain even after the virus has been cleared.

During this time, he suffered fluctuating symptoms of chest tightness, insomnia, headaches, poor concentration and extreme fatigue and had to self-isolate for large parts of this time.

“Given the persistent positive PCR tests and impact on his health and mental health, we decided on a unique therapeutic approach,” said Professor Stephen Jolles, Clinical Lead at the Centre and Honorary Professor at Cardiff University’s School of Medicine.

“We wondered whether therapeutic vaccination could help in finally clearing the virus by inducing a strong immune response within the body.

“We administered two doses of the BioNTech Pfizer vaccine, one month apart, and very quickly saw a strong antibody response, much stronger than had been induced by the prolonged natural infection.”

Researchers at the Centre, based at the University Hospital of Wales in Cardiff, also saw a strong T-cell response – the arm of the immune system thought to be crucial to fighting off the virus.

Dr Mark Ponsford, a clinician scientist from Cardiff University’s School of Medicine, said SARS-CoV-2 clearance was finally confirmed 72 days after the first vaccination dose, and 218 days since it was first detected.

“It was a pretty astonishing moment,” he said.

“To our knowledge, this is the first time mRNA vaccination has been used to clear persistent COVID-19 infection. Importantly, the vaccine was well tolerated by the patient and successfully induced a strong antibody and T-cell response. This was remarkable given Ian’s response to conventional vaccinations in the past has been extremely limited.”

Scientists will need to reproduce this work to confirm the link and see if it can be used in other cases.

“We have all seen how vital vaccination is to the ongoing fight against the global pandemic – but our study is the first to highlight the exciting potential for it to be used as a treatment in persistent infection,” said Dr Ponsford.

“While genetic causes of immunodeficiency are rare, there are many more individuals whose immune system have been suppressed because of their medical conditions and treatments. We should be alert to persistent COVID-19 infection in this setting and develop the tools to respond accordingly.”