Should you avoid there is/there are at the beginning of a sentence?
The short answer: Yes.
Is it incorrect? No.
But let’s be honest, you can do better. Using “there is” or “there are” sounds a little Dick-and-Jane, and readers expect more from you, unless you’re using it for emphasis. These phrases, although not curse words, are called “expletives,” and they are unnecessary and inefficient, according to the Purdue Online Writing Lab. They also often lead to using passive voice, which goes against our grain.
Example
Original: There are three COVID-19 vaccine doses that should be obtained to help prevent contracting the virus and reduce the risk of hospitalization.
Receiving three doses of a COVID-19 vaccine helps you to avoid contracting the virus and reduces the risk of hospitalization.