According to a new study, two out of every five people with compromised immune systems have a “low or undetectable” antibody response after receiving two vaccinations.

While the vaccines appear to be effective in all adults, the researchers believe their findings support the development of a third coronavirus vaccine in groups with low or no antibody responses.

Vaccination experts are expected to make an immediate recommendation on whether a booster campaign is required in the autumn.

The discovery comes at a time when weekly Covid-19 deaths have reached an all-time high since March. According to the Office for National Statistics (ONS), 571 deaths registered in England and Wales in the week ending August 13 mentioned Covid-19 on the death certificate, an increase of 8% from the previous week.

Experts from the Universities of Glasgow and Birmingham compared the immune responses of 600 patients with immune-mediated inflammatory diseases, such as cancer, inflammatory arthritis, kidney or liver disease, or patients undergoing a stem cell transplant, and 231 healthy individuals after they received both doses of either the AstraZeneca or Pfizer drugs.

They ran immune tests on blood samples, looking not only at antibody levels but also at the ability of a specific type of white blood cell known as a T cell to respond to the vaccine.

Three out of every five people in the vulnerable groups had an antibody response similar to that of healthy adults.

However, compared to healthy people, 40% had a low antibody response, according to the study, which was published as a pre-print in The Lancet.

Furthermore, more than one-tenth (11%) of those who were double-jabbed failed to produce any anti-spike antibodies four weeks later. However, the authors emphasized that almost all of the people who did not have an antibody response had vasculitis, a group of rare diseases that cause inflammation of the blood vessels, which can cause tissue damage.

They stated that the T cell response was similar to healthy adults across almost all patient groups, indicating that some type of immunological response had been mounted, even among those with undetectable antibody levels.

The vaccine is “immunologically active” in all patients, according to the researchers, but their findings support an autumn booster campaign among some groups who had a low response. They added that their study was not a clinical effectiveness study and that work to assess vaccine effectiveness among the most vulnerable is still ongoing.

“The majority of the patients in the Octave trial have mounted an immune response that looks remarkably similar to a healthy control group, 60 percent or so of our people with these rather significant conditions are in fact looking effectively the same as people who are otherwise have an unimpaired immune system,” said trial lead professor Iain McInnes from the University of Glasgow. Blood tests revealed that people with ANCA-Associated Vasculitis, a group of autoimmune diseases that cause the destruction and inflammation of small blood vessels, had a particularly low response.

The research is still ongoing, and the researchers hope to collect data on approximately 3,000 immunocompromised people in total.

Researchers intend to expand their study to look at the effect of boosters on clinically vulnerable groups.

The discovery comes as vaccination experts debate whether a booster program is required in the United Kingdom.

Some people in the United States and Israel are already being offered a third coronavirus vaccine. Officials have yet to confirm whether this will also take place in the United Kingdom.

The study was released at the same time that the Office for National Statistics (ONS) released data on all deaths registered in England and Wales.

Covid-19 was mentioned on the death certificate in 571 cases, accounting for 5.5 percent of all deaths.

It is the highest total since 719 people died in the week ending March 26.

Covid-19 was recorded on the death certificates of 57 care home residents who died during the same week.

According to the ONS, there have been 156,958 deaths in the UK where Covid-19 was mentioned on the death certificate.