Safety of trivalent inactivated influenza vaccine in children 6 to 23 months old.
BACKGROUND
Beginning with the winter season of 2004-2005, influenza vaccination has been recommended for all children 6 to 23 months old in the United States. However, its safety in young children has not been adequately studied in large populations.


OBJECTIVE
To screen for medically attended events in the clinic, emergency department, or hospital after administration of trivalent inactivated influenza vaccine in children 6 to 23 months old.


METHODS
Retrospective cohort using self-control analysis, with chart review of significant medically attended events at 8 managed care organizations in the United States that comprise the Vaccine Safety Datalink. Participants were all children in the Vaccine Safety Datalink cohort 6 to 23 months old who received trivalent inactivated influenza vaccine between January 1, 1991, and May 31, 2003 (45,356 children with 69,359 vaccinations).


METHODS
Any medically attended event significantly associated with trivalent inactivated influenza vaccine in risk windows 0 to 3 days, 1 to 14 days (primary analysis), 1 to 42 days, or 15 to 42 days after vaccination, compared with 2 control periods, one before vaccination and the second after the risk window. All individual ICD-9 codes as well as predefined aggregate codes were examined.


RESULTS
Before chart review, only 1 diagnosis, gastritis/duodenitis, was more likely to occur in the 14 days after trivalent inactivated influenza vaccine (matched odds ratio [OR], 5.50; 95% confidence interval [CI], 1.22-24.81 for control period 1, and matched OR, 4.33; 95% CI, 1.23-15.21 for control period 2). Thirteen medically attended events were less likely to occur after trivalent inactivated influenza vaccine, including acute upper respiratory tract infection, asthma, bronchiolitis, and otitis media. After chart review, gastritis/duodenitis was not significantly associated with trivalent inactivated influenza vaccine (matched OR, 4.00; 95% CI, 0.85-18.84 for control period 1; matched OR, 3.34; 95% CI, 0.92-12.11 for control period 2).


CONCLUSIONS
In the largest population-based study to date of the safety of trivalent inactivated influenza vaccine in young children, there were very few medically attended events, none of which were serious, significantly associated with the vaccine. This study provides additional evidence supporting the safety of universally immunizing all children 6 to 23 months old with influenza vaccine.
Hambidge
Simon J
SJ
Clinical Research Unit, Kaiser Permanente Colorado, Denver, CO 80237-8066, USA. simon.hambidge@dhha.org
Glanz
Jason M
JM
France
Eric K
EK
McClure
David
D
Xu
Stanley
S
Yamasaki
Kristi
K
Jackson
Lisa
L
Mullooly
John P
JP
Zangwill
Kenneth M
KM
Marcy
S Michael
SM
Black
Steven B
SB
Lewis
Edwin M
EM
Shinefield
Henry R
HR
Belongia
Edward
E
Nordin
James
J
Chen
Robert T
RT
Shay
David K
DK
Davis
Robert L
RL
DeStefano
Frank
F
D015331:Cohort Studies; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000009:adverse effects*; D011159:Population Surveillance; D012044:Regression Analysis; D012189:Retrospective Studies; D012306:Risk; D014481:United States; D015164:Vaccines, Inactivated
D007252:Influenza Vaccines; D015164:Vaccines, Inactivated