No, they are not. What determined whether or not a dog is hypoallergenic isn’t the length of its hair or the severity of its shedding but the type of its dandruff and saliva – the things dog hairs carry around the air. So, even though short-haired dachshunds don’t shed all that much and don’t have a lot of hair, they are not hypoallergenic.
That being said, they are obviously better for people with allergies than many other breeds because they are smaller. If you groom a mini short-haired Doxie regularly and if you clean and air out your home daily, a person with light allergies may actually feel all right.