KYIV, Jan 6 (Reuters) - Ukraine is now offering booster doses of COVID-19 vaccines to all adults as the Omicron variant is spreading and is likely to lead to a spike in coronavirus infections next month, Health Minister Viktor Lyashko said on Thursday. Following several periods of strict restrictions, the average daily number of coronavirus cases in Ukraine fell in early January to about 4,000 from above 10,000 in early December. "The medical system is preparing for another increase in the number of COVID-19 cases in Ukraine," Lyashko said in a post on Facebook. "We call on all Ukrainians to make a conscious choice in favour of vaccination against coronavirus disease and help us overcome the epidemic," he said, adding that all vaccinated citizens over 18 years old will be eligible for a booster shot of either the Pfizer (PFE.N) or Moderna (MRNA.O) COVID-19 vaccines. Ukraine detected its first case of Omicron in December, saying that the infected person had recently returned from the United Arab Emirates. In the country of 41 million people, only 13.9 million have received two jabs of vaccines. The country has recorded 97,000 deaths from COVID-19 since the pandemic began.