Vacuum sealing meat including sausages helps to make the sausage or meat stay fresher longer however it doesn't make it last any longer in the refrigerator.
Still vacuum sealed sausage or any other meat will last from 3 to 5 days in the refrigerator but it's best to freeze the vacuum sealed sausage or meat if you plan to keep it longer than 3 days.
If you keep the vacuum sealed sausage or meat frozen it will last from 6 months to a year but if you don't freeze the vacuum sealed sausage be sure to use it within 3 days for the best freshness and taste and to prevent it from going bad.
If you kept the vacuum sealed sausage in the refrigerator longer than 4 days then it is likely bad and should be thrown out to prevent illness from the food.