Safety of live attenuated Japanese encephalitis vaccine given at the age of 9 months in National Immunisation Programme of Sri Lanka.

OBJECTIVES: This study was designed to describe the safety profile of the single dose live attenuated Japanese encephalitis vaccine (LJEV) SA-14-14-2 given at the age of 9 months in the National Immunisation programme of Sri Lanka.

METHODS: cohort event monitoring (CEM) was conducted in the Jaffna district during November 2012 to January 2015. A representative sample of 3041 infants who received the LJEV at the age of 9 months was followed up actively over telephone interviews on days 1, 3, 14, 30 and 45 for adverse events (AE). Parents were encouraged to self-report in between these interviews. When an AE is notified, further clinical information was obtained through in-depth interviews and home/hospital visits to determine as an adverse event following immunisation (AEFI). Investigators independently reviewed each AEFI for consistent causal association with LJEV according to WHO causality assessment.

RESULTS: Of the 2878 (94%) infants who completed the follow up of 14 days, 911 (32%) experienced 1423 AEFIs. Of them, 376 (26%) were identified as AEFI with consistent causal association to LJEV (AEFIc). Irritability (53/ 1000 doses administered) and fever ≥100.4° F (46/1000 doses administered) accounted for 41% and 35% of AEFIcrespectively. Majority of AEFI (940) were identified as inconsistent as there were alternate causes. Nineteen AEFIc in 14 infants were classified as serious since they led to hospitalisation. Of the 2392 (79%) infants who completed 45 days follow up, 1022 experienced 1804 AEFI during 15-45 days. Only 20 were identified as AEFIc. There were no reported fatal or life threatening AEs.

CONCLUSIONS: LJEV administered to infants at 9 months was devoid of any significant safety concerns as most of the AEFIs were non-serious and resolved completely. CEM is a useful method for AEFI surveillance.