As the evidence base around COVID-19 has developed in recent months, testing policy has become a vital component in every country's response to the pandemic. In England, trusts have worked with partners across public health, the independent sector and government, doing all they can to help expand testing capacity. This article looks at one specific strand of testing – the antibody test.

By using high-level data and some anecdotal evidence from around a fifth of trusts, it is possible to explore some initial trends around the prevalence of antibodies in the NHS workforce.

Although little is known about the role of antibodies and the likelihood of reinfection after recovery from COVID-19, this preliminary research builds on what we already know. It highlights just how important regular antigen and antibody testing is for protecting and providing peace of mind to the NHS workforce that are working so hard to respond to COVID-19 and reopen non-COVID services.


Testing NHS staff

As the pandemic unfolded, the government scrambled to increase testing capacity in England, rolling out a national antigen testing programme in order to confirm positive COVID-19 cases. Following national measures to curtail the infection rate, many NHS staff found themselves in the position of needing to self-isolate for seven or 14 days.

Depending on region and type of provider, trusts reported varying levels of staff absence. During the peak of the pandemic, trusts in some areas told us that up to 20% of their workforce were absent – a new workforce conundrum. Quickly a distinct strand of testing for NHS and care staff, other key workers and their households was set up, called pillar two.

During the peak of the pandemic, trusts in some areas told us that up to 20% of their workforce were absent.


The introduction of pillar two testing made antigen tests available to both symptomatic key workers and their households or those that had been in contact with a confirmed case. This strategy was put in place to help protect employees, provide assurance to staff and patents, and to relieve workforce concerns. By the middle of May around 65% of all daily tests fell within the pillar two strand.

As confirmed infections continued to climb, reports of deaths among the health and care workforce further highlighted the vital importance of protecting and placed the protection and testing of all staff at the heart of every trusts' response to coronavirus.


Have I had COVID-19?

From February to May many people who were mildly symptomatic did not have access to antigen tests. In addition, evidence from across the world suggests that a certain amount of the population that test positive for COVID-19 experience no symptoms. Similarly, a proportion of people who are tested and found to have the appropriate antibodies were not aware of any infection. In England, the lack of a national test and trace system in the first three months of the pandemic and the initial time it took to expand testing capacity has left much of the population asking one question – have I had coronavirus?

The Office of National Statistics weekly infection survey showed that between 26 April and 26 July, 6.2% of people tested positive for antibodies against SARS-CoV-2 on a blood test, suggesting they had the infection in the past.

Public Health England has also been monitoring the prevalence of antibodies in routine blood donations. The results show that the proportion of the population with antibodies has increased from week 13 to week 18 in 2020 but there is significant variation across different regions. By week 18, 17.5% of the population were found to have antibodies, compared to figures below 5% in the South East, South West and North East.


The debate over the usefulness of the antibody test continues

Little is known about how and when the body builds up an immunity to the virus. If the virus works in a similar way to other comparable viruses, antibodies are produced in the body which can be traced in blood tests. The prevalence of antibodies can vary, as can the length of time they are present. It is also not known if having antibodies provides any protection from being re-infected.

Issues surrounding reliability (varying levels of false negatives and false positives) and determining the optimal time to test for antibodies have, for many, cast doubt on how useful the test is. Given the lack of concrete evidence in the area, the presence of antibodies in the NHS workforce has little influence in clinical practice or how staff can be deployed.

But despite the drawbacks, many staff have wanted to know the outcome of the test. Furthermore, widespread testing of NHS staff also adds to the evolving evidence base and could help inform future testing strategies.


Antibody testing findings from 42 trusts and three systems

After the government procured an antibody test fit to distribute, trusts across England have tested as many staff as possible. At the end of June, NHS Providers asked trust chief executives to share the results of antibody testing programmes. 45 chief executives provided data covering 42 trusts and three integrated care systems; accounting for around a quarter of the provider sector. This has created a useful snapshot into trust’s results, although due to the sample size, the picture is incomplete.

There are also several variables that are likely to impact on the results, including trusts prioritising high risk staff for tests, trust type, local infection rates, and staff demographics. At the time of reporting, some trusts and systems had tested all staff, and others were working hard to increase the number. The results also do not provide a representative sample across trust type.

With these caveats in mind, the results must be treated with caution. They provide some initial insight, but full academic exploration covering a bigger sample is needed to understand the prevalence of antibodies in the NHS workforce.


Key findings:

  • across the 45 responses, on average 17% of staff were found to have tested positive for antibodies
  • the minimum proportion of staff with antibodies was 3.5% and the maximum was 40%
  • when looking at the average proportion of staff with antibodies by region, London recorded the highest with 27% and the East of England was next with 18%
  • the South West and North East and Yorkshire regions recorded the lowest proportion, where on average 11% of staff tested positive for antibodies
  • the four trusts that recorded the highest proportion of positive staff are in London, the fifth in the North West
  • three out of the five trusts with the lowest levels are in the South West with the remaining two in the Midlands and North West


The main theme is the huge variation across trusts. The region of the trust seems to be a much stronger driver than trust type. These findings broadly echo a similar pattern shown from the PHE antibody prevalence study in blood donors.

Following a cursory analysis, it was not possible to detect any relationship between the number of patient COVID-19 deaths and a higher prevalence of antibodies in staff. There were cases of higher levels of antibodies in trusts where there were very few deaths – including a specialist trust that only provides non-COVID services.

In addition to the results, two trust chief executives told us that across their workforce, a greater proportion of Black, Asian and minority ethnic staff were found to have antibodies than levels among white staff.



Although a very small sample, the results of the antibody test from 45 chief executives have confirmed themes found elsewhere. Locality seems to be a more important driver for both the spread of the virus and the prevalence of antibodies. The results reflect others that continue to highlight how London and the Midlands have to date been more impacted by COVID-19 than say, the South West. However, this could easily change with a second wave or localised surges. We need to continue to add to the body of emerging evidence in this area so that trust leaders can make evidence-based decisions to best support and protect their staff.

Antigen and antibody testing of NHS workers remains an ongoing priority for trust leaders and must be a fundamental arm of any national testing strategy. Everything that can be done to ensure staff are safe and protected at work must continue. This requires consistent and regular testing, alongside other protective measures to keep employees and patients safe. Only by providing trusts and staff with clear guidance, adequate testing capacity and good turnaround times, will they have the assurances needed to keep as many staff on the frontline as possible.