Foreign travellers can opt to show a rapid antigen test or a PCR test to enter Greece, the country said on Thursday, amending a rule it announced only the day before to help curb the spread of the Omicron variant of the coronavirus. Health authorities said on Wednesday that the measure - which will be in effect from Dec. 19 - would require a PCR test for no more than 48 hours old including those from other EU countries for anyone aged 5 years and up. Previously, proof of vaccination or recovery from COVID-19 or negative testing was necessary to travel to Greece. On Thursday, slightly broader options for the testing were announced - with all travellers aged over five needing to show either a PCR test was taken no more than 72 hours before their arrival or a rapid test 24 hours before arriving. "The Omicron variant prompted our country to take one-off measures for foreign visitors," government spokesman Giannis Oikonomou said. He said the restrictions would apply for the Christmas period and were aimed to delay the spread of the pandemic to give Greek people more time to get booster shots. Meanwhile, Greek health authorities are concerned about the high viral load on the island of Crete, where the first case of Omicron was identified earlier this month. The possibility of closing schools is on the table. Crete is the only region, say epidemiologists, where the viral load is not dropping. Additionally, they are warning of a surge in Covid-19 cases in January after the holiday season. Many health experts are calling for restrictions such as shutting down schools and clubs. Meanwhile, a recent study has found that the Omicron variant of Covid-19 infects 70 times faster than the previous Delta strain but is less severe. In the last 24-hour period, Greece reported 4,696 coronavirus cases and 96 deaths.