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Background: Limited data are available regarding the predictive value of various symptoms for pediatric influenza illness.
Objectives: To identify symptoms associated with culture-confirmed influenza illness in children receiving live attenuated influenza vaccine (LAIV), trivalent inactivated influenza vaccine (TIV), or placebo
Methods: In 5 prospective studies of LAIV compared with placebo or TIV in children aged 6 months to 17 years, symptoms were collected for respiratory illnesses during 5- to 8-month surveillance periods. Symptoms associated (odds ratio [OR]>2.0) with positive influenza culture were determined using logistic regression (P<0.05).
Results: Study 1 (children 11-23 months; 4532 samples): fever (OR 11.7 for LAIV, 6.0 for placebo) and cough (3.2 LAIV, 2.6 placebo) were predictive; sore throat (3.8) was also predictive for placebo. Study 2 (15-71 months; n=4837): fever was predictive (4.3 LAIV, 6.6 placebo); for placebo, cough (3.2) and headache (2.7) were also predictive. Study 3 (6-71 months, n=4060): fever (2.4 LAIV, 17.3 TIV) and headache (5.8 LAIV, 4.3 TIV) were predictive; for LAIV, runny nose (19.1) and decreased activity (2.6) were also predictive. Study 4 (6-59 months; n=16,206): fever (3.6 LAIV, 4.4 TIV), headache (2.3 LAIV, 2.1 TIV), and runny nose (1.6 LAIV, 2.1 TIV) were predictive. Study 5 (6-17 years; n=2320): fever (4.6 LAIV, 4.4 TIV), cough (3.0 LAIV, 3.0 TIV), decreased activity (2.3 LAIV, 2.0 TIV), and headache (2.2 LAIV, 2.2 TIV) were predictive.
Conclusions: Consistent with previous studies, among unvaccinated children, fever, cough, sore throat, and headache were most strongly associated with positive influenza culture. Similar results were seen among vaccinated older children. Among vaccinated younger children, fever, runny nose, and headache were most strongly associated with influenza; the association with fever was stronger for TIV versus LAIV recipients, consistent with prior observations of greater incidence of fever among TIV versus LAIV recipients who develop influenza despite vaccination. Sponsored by MedImmune, LLC.