Scientists have developed a test that can measure both the T-cell and antibody response to coronavirus in a single blood sample.
Researchers say the approach can also be used to measure the immune response to vaccination and previous infection.
Antibodies are just one arm of the body’s immune response, and for some people this response is weak and short-lived.
Researchers believe T-cell immunity plays a much greater role in protecting people from future infection, however large-scale testing has proven more challenging.
Antibodies bind to the body’s foreign invaders and tell the immune system it needs to take action.
T-cells are a type of white blood cell which hunt down infected cells in the body and destroy them.
Dr Martin Scurr, a research associate at Cardiff University’s School of Medicine, and lead author on the study, said: “Covid-19 infection rates remain alarmingly high – and it is clear infection even after vaccination is an issue.
“To help control future outbreaks and identify at-risk individuals, it is important to understand the exact make-up of the immune response to Covid.
“Our test accurately detects both the T-cell and antibody response to the virus in one blood sample.
“Together these indicators represent a powerful measure of immunity from Covid-19.
“The test can be made widely available, is easy to employ and cost effective, and should play a very useful role in monitoring this pandemic, for instance by identifying individuals at greater need of booster jabs.”
In the new study, the researchers took a small sample of blood from individuals of all ages, 68 with underlying cancer and 231 healthy donors.
They stimulated T-cells with small pieces of the virus. The T-cells recognise these pieces if the individual has been previously infected (or vaccinated) and produce chemicals called cytokines which can be easily measured.
The size of the T-cell and antibody responses was also monitored in a group of individuals tested before, during and after the UK’s Covid-19 vaccination campaign.
Researchers found that while both vaccine doses were needed to maximise the T-cell response against the virus, previously infected individuals required only one dose to achieve comparable immune responses.
According to the study, the test was most useful in monitoring immune responses in patients considered more at risk from Covid-19, even after vaccination.
The study found the second vaccine dose was essential for cancer patients.
Among cancer patients recruited from Velindre Cancer Centre in Cardiff, two doses induced T-cell and antibody responses to equivalent levels as healthy donors, the researchers found.
In some cancer patients there was a dramatic fall in immune responses at three months, highlighting the importance of monitoring these responses.
Professor Andrew Godkin, co-senior author from Cardiff University and the University Hospital of Wales, said: “Without this sort of information there is uncertainty around whether repeated booster vaccinations will be required in future, and who in particular will need them.
“This data is crucial for understanding how and when to offer re-vaccinations to different groups.”
The team will also monitor whether T-cell and antibody responses induced by vaccination can protect against mutant variants of coronavirus, including the Delta variant.
Danny Altmann, professor of immunology at Imperial University, said: “This study is important in both demonstrating the ease of measuring immune responses using a whole blood approach, but also the importance of monitoring susceptible individuals and healthy controls for differences in vaccine response and future potential loss of protection.
“Long-term monitoring will be crucial to understand and quantify this problem.”
The test was developed in collaboration with Wales-based biotechnology company ImmunoServ Ltd and is outlined in a study published in the journal Immunology.
The research was funded by UK Research and Innovation as part of its response to the pandemic, along with the Medical Research Council and Cancer Research Wales.