THE HEALTH SERVICE Executive will invite more than 5,000 people to take part in a new study which aims to measure exposure to Covid-19 across the Irish population.

The study hopes to identify people who have antibodies for the virus and add to the HSE’s knowledge about what protection they may have against re-infection.

Antibodies are are special proteins produced by the body’s immune system to help fight disease. They are usually produced when an individual contracts an illness, although they are also produced when a person is vaccinated.

The presence of Covid-19 antibodies would indicate that a person was infected with the virus, regardless of whether they had a severe mild or even asymptomatic case of the disease.

Health officials here have previously warned that levels of Covid-19 antibodies in the population here are very low – between 1% and 5%.

This would mean that even if there is some immunity after recovering from Covid-19, very few people would have it.

It also remains unclear if a person with Covid-19 antibodies is protected from the virus in future and World Health Organisation officials have previously acknowledged the limited data available on immunity.

The HSE will now send 5,000 letters to people in Dublin and Sligo, with those who participate in the study set to be representative of the wider population.

Last month, Dr Cillian De Gascun, Director of the National Virus Reference Laboratory, said the new study was being planned to obtain “an overall picture of what’s happening in the population at large”.

The health service said that Dublin and Sligo were selected as sample locations because they represent areas of the country with higher and lower known levels of infection.

The intention is to repeat the antibody research in other areas of the country over the coming year.

The initial results are expected in late August and will enable the Health Protection Surveillance Centre (HPSC) to estimate the level or prevalence of Covid-19 infection across different age groups.

The HSE’s National Clinical Director for Health Protection, Dr Lorraine Doherty, said the test would be highly important to the health service’s ongoing response to Covid-19.

“When the results are available, we will have valuable information on the level of infection by age group and also the extent of asymptomatic infection, informing our national public health responses to Covid-19,” she said.

Those who consent to take part in the study will be asked to complete a short questionnaire by phone, carried out by trained staff on behalf of the HPSC.

They will also be asked to provide a blood sample to test for antibodies, which will be taken by a phlebotomist in a local centre arranged by the HSE.

Participants will be provided with individual results and those who are found to have antibodies for Covid-19 will be asked to take part in a follow-up study, which will include further questions about symptoms and three more blood tests over a 12-month period.

De Gascun cautioned that the test would only be useful for the health service, as opposed to the individuals taking part.

“The main benefit of this testing is at the population level; individuals will be advised not to use their result as a basis for clinical decisions about diagnosis or management,” he said.

The study is not open to volunteers from the general public and the HSE is encouraging those who receive a letter to consider participating.