Russian to English Medical Medical: Health Care

The certificate of preventive vaccinations (page 9) includes the list of vaccines and mentions one of them 'жкв' ('живая коревая вакцина' or live measles vaccine) the date of the vaccination and obscure "0.5 с". I need to know the meaning/translation of "c" letter in "0.5 c" record by the doctor.

Example of the record: 09/01/07 ЖКВ 0.5 С 785 (подпись).

The "0.5 c" is included for all the vaccines in the certificate (measles, mumps, rubella). Is it a quantity (but it doesn't look like cubic cm) or what is it?