The Health Service Executive is writing letters to more than 5,000 people, inviting them to take part in a study to measure exposure to Covid-19.
Those who take part will be asked to complete a questionnaire and provide a blood sample. The letters are being sent to people in Dublin and Sligo to invite them to take part in the study.
It will measure exposure to Covid-19 in the population using an antibody blood test in counties with some of the highest and lowest levels of infection.
The HSE said that using a random sample of participants from both locations will make it possible to provide an overall national estimate of infection in the population.
Those who agree to take part will be asked to complete a short questionnaire over the phone. They will also be asked to provide a blood sample to test for antibodies.
Those found to have antibodies will be asked to take part in a follow-up study.
The HSE said the research will help provide information about how long antibodies last and what protection they provide against new infections.
It said those who participate are contributing to essential research of benefit to society. It is expected the initial results are expected in late August.
The HSE said a public awareness campaign to encourage more people to use face coverings will also get under way today.
Authorities are encouraging people to wear them on public transport, in shops and anywhere else where social distancing may be difficult.