Many dialysis patients remain vulnerable to Omicron
New laboratory data from our researchers working at the Francis Crick Institute, published this week as a Research Letter in The Lancet, show that, even after vaccination, patients receiving in-hospital dialysis treatment are less likely to be protected against infection by the Omicron variant.
Omicron is now the dominant Covid-19 variant in the UK. Although this variant is less severe than Delta, Omicron can still cause serious illness in clinically vulnerable groups.
Are the vaccines effective against Omicron?
The virus that causes Covid-19 – SARS-CoV-2 – is covered in a protein called spike that it uses to get into our cells. Covid-19 vaccines stimulate the body to produce antibodies against spike. The Omicron variant has over 30 mutations in the spike protein compared to the original virus on which all the vaccines are based. This means that the vaccines are less effective at preventing infection, but are still good at preventing severe disease in younger, healthy people with normal immune systems.
Kidney patients are vulnerable to Covid-19 infection
Kidney patients who need to travel to hospital several times a week for life-saving dialysis treatment are unable to ‘shield’ and are therefore particularly vulnerable to catching Covid-19. Needing dialysis, and some of the treatments for kidney disease, cause the response to vaccination to be reduced in kidney patients. Currently, unless they are also taking immunosuppressive drugs, or have other immune-compromising conditions, dialysis patients are considered ‘fully vaccinated’ after two vaccine doses and ‘boosted’ after three.
Understanding whether kidney patients are protected by the vaccines
Last year, we joined forces with the National Kidney Federation (NKF), Kidney Wales, the PKD Charity and several Kidney Patient Associations to fund a study, NAOMI (neutralising antibody after COVID vaccination in haemodialysis patients), to discover how well Covid-19 vaccines work in patients who receive dialysis treatment in hospital.
Dr Edward Carr and Dr Rupert Beale at the Francis Crick Institute along with Dr Michelle Willicombe and Dr Steve McAdoo from Imperial College London, are using a novel high-throughput method developed at the Crick to measure patients’ immune responses to Covid-19 vaccines.
While some groups have studied the levels of antibodies that bind the SARS-CoV-2 spike protein to try to gauge patients’ immune response to vaccination, none of these studies have looked specifically at a group of antibodies called neutralising antibodies. These are difficult antibodies to test for because you need to work with live cultures of the SARS-CoV-2 virus. However, these antibodies provide the most important kind of protection against infection because they bind to the spike protein and stop the virus entering cells. Viruses that are covered by neutralising antibodies are also recognised for destruction by the immune system. Data from previous studies suggest that neutralising antibody levels are a good predictor of how well a vaccine works and how well the recipient is protected. Using their test, the team can easily test for neutralising antibodies against multiple different Covid-19 variants, including Omicron.
In August, we shared the first results from this study, comparing neutralising antibodies in kidney patients who receive in-hospital dialysis after two doses of either the Pfizer/BioNTech or the Oxford/AstraZeneca vaccine. The researchers found that those who had received the Pfizer/BioNTech mRNA vaccine had six-times higher levels of neutralising antibodies against the Delta variant than patients vaccinated with the Oxford/AstraZeneca vaccine.
Since this paper was published, the team have been investigating immune responses before and after three vaccine doses and they have also been able to test for neutralising antibodies against the Omicron variant.
New results
In the new paper, the team measured the levels of neutralising antibodies against the Omicron and Delta variants in 98 patients who travel to hospital for dialysis sessions at around 158 days after their second dose of vaccine and at around 27 days after their third vaccine dose. Patient samples were gathered by researchers in Leicester and Cambridge. The patients’ first and second doses were either Pfizer/BioNTech or Oxford/AstraZeneca. All patients received the Pfizer/BioNTech vaccine for their third dose.
After two doses of the Oxford/AstraZeneca vaccine, most patients’ antibody levels against both Delta and Omicron were too low to be detected. Most patients who received the Pfizer/BioNTech vaccine did produce antibodies against the Delta variant but their antibody levels against Omicron were undetectable.
The team assessed neutralising antibodies after a third dose of the Pfizer/BioNTech vaccine was given to all patients. Less than half of patients who had received the Oxford/AstraZeneca vaccine for their first two doses showed a detectable antibody response to Omicron. Those patients who had received three doses of the Pfizer/BioNTech vaccine had four-times higher levels of neutralising antibodies against Delta than they did after two doses, and although many of them also developed detectable antibodies against Omicron, a substantial minority did not.
These findings suggest that patients who travel to hospital for dialysis treatment will likely benefit from a fourth vaccine dose to increase protection against the Omicron variant. We are grateful to all of the patients and researchers involved in this study.
Dr Aisling McMahon, Executive director of Research, Innovation and Policy at Kidney Research UK, said: “As the pandemic continues, it is extremely important that we continue to monitor how well the vaccines are protecting kidney patients. These findings clearly show that many patients on dialysis are still vulnerable to Covid-19 infection, particularly the Omicron variant, even after three vaccine doses. We believe this study provides strong evidence that patients who travel to hospital for dialysis should receive a fourth vaccine dose to ensure they have the best protection possible.”
Edward Carr, postdoctoral clinical fellow in the Crick’s Cell Biology of Infection Laboratory, said: “Patients in need of kidney dialysis treatment are making regular visits to hospital and are also more vulnerable to severe COVID-19 infection. Some of these patients are considered to be immunocompromised because of the medication they’re taking or their comorbidities. Currently, just these patients - and not all dialysis patients - are automatically offered a fourth vaccine dose.
“Our data supports fourth doses for all kidney dialysis patients to maximise levels of protection in this group.”
Rupert Beale, head of the Crick’s Cell Biology of Infection Laboratory, said: “New variants will continue to arise as the pandemic evolves, and for vulnerable patients, it’s especially important to assess the specific risks. We’ve shown that Omicron has raised the threshold for effective protection and that patients undergoing dialysis shouldn’t assume protection after three doses. Our study suggests four doses of vaccine would benefit dialysis patients.”
