Subcutaneous nodules following immunization in children; in Victoria, Australia from 2007 to 2016

Subcutaneous nodules are a rare adverse event following immunization (AEFI). We aimed to describe nodules at the injection site reported to SAEFVIC (Surveillance of Adverse Events Following Vaccination in the Community) using the Brighton Collaboration Case Definition (BCCD), management and recurrence following subsequent immunizations.

We assessed 58 cases (<18 years of age) of 'nodule at injection site' reported to SAEFVIC, Melbourne, Australia, between May 2007 and June 2016. Case details were analyzed from records and phone interview follow-up. The Australian Immunization Registry was reviewed for immunization status.

71% (41/58 reported cases) were consistent with the BCCD for subcutaneous nodule, 14% (8 cases) were 'possible subcutaneous nodules', 10% (6 cases) were nodules associated with BCG immunization and 5% (3 cases) were attributable to an alternative diagnosis. The median age at immunization was 12 months, (range 1 month-12 years); 54% male (22/41 cases). 17% (7 cases) had multiple nodules. Nodules were associated with immunizations containing aluminum (74%, 36/49 nodules), no aluminum (8%, 4 nodules) and unknown (18%, 9 nodules). Most cases developed symptoms within 3 days post-immunization (59%, 24 cases) and in the thigh (59%, 29 nodules). Pruritus was associated in 41% (17 cases). Around 1/3 (34%) of nodules resolved 6 months post immunization, 2/3 (68%) by 12 months, however 1/4 (24%) remained persistent for >24 months. 5 cases had prior nodules and 1 case had recurrence with subsequent immunization. 83% (34 cases) were fully immunized for age at follow-up.

Subcutaneous nodules at the injection site may occur following a wide range of vaccines, including vaccines without aluminum. All cases require careful review and where possible, specialist management and to support subsequent immunizations.