What is the most common condition among the patients who received influenza seasonal injectable preservative free immunization?
the most common condition refers to MAX(DESCRIPTION) from conditions; patients who received influenza seasonal injectable preservative free immunization refer to PATIENT where DESCRIPTION = 'Influenza seasonal injectable preservative free' from immunizations;
SELECT T2.DESCRIPTION FROM immunizations AS T1 INNER JOIN conditions AS T2 ON T1.patient = T2.PATIENT WHERE T1.DESCRIPTION = 'Influenza  seasonal  injectable  preservative free' GROUP BY T2.DESCRIPTION ORDER BY COUNT(T2.DESCRIPTION) DESC LIMIT 1