VIENNA, Nov 23 (Reuters) - Austria"s COVID-19 lockdown will have a "very small" effect on economic output this year but the current fourth wave of infections will probably inflict damage next year, the head of a top economic think-tank said on Tuesday. Austria went into its fourth full COVID-19 lockdown on Monday, the first western European country to take the drastic step this autumn in the face of surging infections and dwindling intensive-care capacity. Restaurants, cafes, bars and non-essential shops are closed except for take-away business for at least 10 days and no more than 20, the government says. "The year 2021 is more or less in the bag," Gabriel Felbermayr, head of think-tank Wifo, which produces gross domestic product forecasts for the government, told a news conference. Wifo"s last predicted GDP growth for this year was 4.4%. "If November and December are significantly worse, there could be a revision. It would be within range. It would be very, very small," he said, adding that a week of lockdown costs about 800 million euros ($901 million) in lost economic output, rising to up to 1.2 billion euros the closer you get to Christmas. This wave of infections could hurt Austrian winter tourism in particular, Felbermayr said, since infections are also high in Germany and the Netherlands, from where many tourists arrive. Tourism accounts directly for about 5% of GDP. Ski lifts are now open but hotels are closed to tourists. "The year 2022 is of course beginning weakly," Felbermayr said. Wifo last predicted 4.8% GDP growth for next year. "It is clear that the current developments will result in a downward revision ... How big it will be will of course depend enormously on what rebound effects there are," he said, adding that GDP growth should remain above 4%. ($1 = 0.8878 euros) Reporting by Francois Murphy; Editing by Nick Macfie Our Standards: The Thomson Reuters Trust Principles.