Last week, Chile announced that it would start offering a fourth dose in February.
Experts are concerned that the pattern of mutations detected on the Omicron variant will mean that the protection generated by the current generation of vaccines may take a partial hit.
Two other booster shots with vaccines made by Pfizer/Biontech and Moderna have already been approved for use in the EU.
The current rules: People who initially received Pfizer or Moderna vaccinations are eligible for a booster six months later if they’re 65 or older, or are at high risk of COVID-19.
The European Medicines Agency said the booster doses may be considered at least 6 months after the second dose for people aged 18 years and older."
The mixing of vaccines comes as the Mideast island nation struggles through its worst wave of the virus despite being one of the top countries in the world in per-capita inoculations.