A flu vaccination campaign is underway among high-risk groups across Mongolia free of charge, the country’s health ministry said Sunday. The annual vaccination campaign is part of efforts to prevent respiratory infections, including seasonal flu, the ministry said in a statement. The high-risk groups include people aged 60 and above, pregnant women, children up to five years old, healthcare workers and others, the ministry said. Mongolia’s climate is strongly continental with long, frigid winters and short, warm summers. A temperature of minus 25 degrees Celsius is normal during winter in Mongolia where the peak flu season runs from December to February. Additionally, the country’s capital Ulan Bator, home to nearly half of the country’s population of 3.4 million, suffers serious air pollution in winter.