BRASILIA, Dec 8 (Reuters) - The Omicron variant of the coronavirus has so far been detected in the Americas in Argentina, Brazil, Canada, Chile, Mexico and the United States, but it is just a matter of time before it circulates in more countries, the Pan American Health Organization (PAHO) warned on Wednesday. The regional health agency said coronavirus infections have turned up in Canada and parts of Mexico, such as Baja California. Except for Panama, Central America is experiencing a steep decline in cases. In South America, there has been a steady increase in Bolivia, Peru and Colombia, while Ecuador, Chile and Argentina are reporting a drop, PAHO said. Research is ongoing to better understand Omicron"s behavior and the potential risks for the Americas, PAHO director Carissa Etienne told reporters on a webcast news conference. "The arrival of a new variant doesn"t necessarily mean that things will be worse, but it does mean that we must be extra-vigilant in the short term," she said. Vaccines remain a critical tool to reduce hospitalizations and deaths and limit the appearance of new variants, PAHO said. So far, 55% of the people in Latin America and the Caribbean have been fully vaccinated against COVID, and 20 countries in the region have yet to reach the year-end vaccination coverage target of 40% set by the World Health Organization. Guatemala, Haiti, Jamaica and St. Vincent and the Grenadines remain far behind, Etienne said. "At the current pace, as many as six countries may not meet the 40% year-end target," she said. PAHO, which is purchasing vaccines for the region through its Revolving Fund, said it has secured deals with AstraZeneca Plc (AZN.L), China"s Sinovac Biotech Ltd (SVA.O) and Sinopharm (1099.HK).