ROME, Italy -- Italy began administering booster COVID-19 vaccine shots on Monday, after the procedure received the official green light from the country's Medicines Agency (AIFA).

As the Health Ministry announced earlier this month, third doses -- of either Pfizer-BioNTech or Moderna vaccines -- will be offered to people with fragile immune systems.

This includes not only immuno-compromised people -- such as transplant patients -- but also elderly people and residents in care homes. Based on guidelines issued by AIFA, healthcare workers will also receive the booster shot.

The third dose will be offered as an option, since vaccination against coronavirus is strongly recommended but not mandatory in Italy.

AIFA has recommended that the third shot should be available at least 28 days after the previous dose for immuno-compromised people.

For those over 80, people living in care homes, and healthcare professionals, the third dose would be considered as a "booster to maintain an effective immune response," and should be administered at least 6 months after their last dose.

Overall, AIFA and the Health Ministry have stressed that the national priority should remain to ensure that a majority of the population is vaccinated.

As of Monday, some 76 percent of the target population (those aged over 12) had been fully immunized, while 82 percent had received at least one dose, data from the Health Ministry has shown.

Since the pandemic broke out in Italy in February 2020, some 4.6 million coronavirus cases have been confirmed. There have been over 130,000 fatalities and 4.4 million recoveries.