How to keep leading zeros in a column when reading CSV with Pandas?

I am importing study data into a Pandas data frame using read_csv.

My subject codes are 6 numbers coding, among others, the day of birth. For some of my subjects this results in a code with a leading zero (e.g. "010816").

When I import into Pandas, the leading zero is stripped of and the column is formatted as int64.

Is there a way to import this column unchanged maybe as a string?

I tried using a custom converter for the column, but it does not work - it seems as if the custom conversion takes place before Pandas converts to int.