Article Figures & Data
Figures
- Figure 1
Flowchart of the study population.
Tables
Study Population Total Study Population CY = 11,493 Immunized in Current Year but No Prior IIV Immunization CY = 2,914 Immunized in Current Year and 1 IIV in Previous 2 Years CY = 2,450 Immunized in Current Year and ≥2 IIVs in Previous 3 Years, Including Prior Year CY = 4,653 Sex (%) Boys 57.9 57.7 57.1 57.6 Girls 42.1 42.3 42.9 42.4 Socioeconomic status score Low 16.4 17.0 16.1 14.6 Middle 50.7 48.5 50.2 54.3 High 32.7 34.5 33.5 31.0 Age group, y (%) 0-5 8.4 20.9 8.8 1.2 6-10 15.6 20.2 19.0 10.5 11-15 45.3 37.5 44.7 48.3 >15 30.7 21.7 27.6 39.9 Health care–seeking behavior; number of consultations (%) 0 90.3 88.7 90.4 92.0 1 6.8 8.1 6.7 5.5 >1 2.9 3.2 2.8 2.6 Out-season RIs in previous year (%) 0 96.5 96.4 97.4 98.1 1 3.0 3.2 2.4 1.5 >1 0.5 0.3 0.2 0.3 Indicated diseases; % yes Preexisting cardiovascular disease 10.7 10.5 10.0 10.2 Chronic lung disease 78.0 79.7 77.3 78.5 Diabetes 8.3 6.3 8.5 9.2 Chronic kidney disorder 0.1 0.1 0.1 0.1 Immunocompromising condition 3.9 3.7 4.6 3.3 Respiratory difficulties with neurologic origin 1.7 1.3 1.8 1.8 Number of indications for IIV (%) 1 97.4 98.3 97.7 96.8 >1 2.6 1.7 2.3 3.2 Incidence of RI during influenza season/100 child-years (95% CI) All ages 18.4 (17.1-19.8) 27.8 (24.7-31.2) 13.1 (10.8-15.7) 13.4 (11.7-15.4) 0-5 y 56.4 (48.6-65.1) 66.2 (55.6-78.2) 37.9 (25.5-54.4) 49.4 (24.1-90.8) 6-10 y 30.3 (26.0-35.0) 30.0 (23.0-38.4) 22.8 (16.1-31.3) 26.9 (19.7-35.9) 11-15 y 13.2 (11.5-15.0) 14.8 (11.3-19.1) 9.4 (6.6-12.9) 12.4 (9.7-14.8) >15 y 9.6 (7.9-11.6) 12.6 (8.5-18.1) 4.5 (2.3-8.0) 10.4 (8.1-13.2) Boys 19.3 (17.6-21.3) 30.0 (25.7-34.7) 14.7 (11.5-18.5) 13.8 (11.5-16.5) Girls 17.1 (15.1-19.2) 24.8 (20.4-29.9) 10.9 (7.7-14.9) 12.9 (10.3-15.9) Number of consultations for RI during influenza season (%) 0 95.2 93.0 96.5 96.3 1 3.0 3.9 2.3 2.5 >1 1.8 3.1 1.2 1.2 CY = child years; IIV = inactivated influenza vaccine; RI = respiratory illness.
- Table 2
Association Between Immunization History and Occurrence of ≥1 RI Episode During Influenza Season
% RI Crude OR Adjusted OR Episodes (95% CI) (95% CI) Immunized in current year but no (recent) prior IIV immunization 7.0 Ref Ref Immunized in current year and 1 IIV in previous 2 years 3.5 0.48 (0.37-0.61) 0.61 (0.47-0.78) Immunized in current year and ≥2 IIVs in previous 3 years, including prior year 3.7 0.50 (0.41-0.62) 0.85 (0.68-1.07) GP = general practitioner; IIV = inactivated influenza vaccine; OR = odds ratio; SES = socioeconomic status; RI = respiratory illness.
Note: Adjusted for SES, age, number of indication categories for IIV, health care–seeking behavior, and number of out-season summer GP-diagnosed RI episodes.
The Article in Brief
Impact of Repeated Influenza Immunization on Respiratory Illness in Children With Preexisting Medical Conditions
Marieke L.A. de Hoog , and colleagues
Background Recent evidence suggests that repeated inactivated influenza vaccine immunization throughout childhood may impair long-term immunity against influenza. This study assessed whether, in children with pre-existing medical conditions, prior immunization altered the effect of inactivated influenza vaccine on respiratory illness episodes diagnosed in primary care during the influenza season.
What This Study Found Repeated inactivated influenza vaccine immunization in children with pre-existing medical conditions has no negative impact on, and may even enhance, long-term protection against respiratory illness. This study, conducted in the Netherlands, examined data for 4,183 children aged 6 months to 18 years with pre-existing conditions who received inactivated influenza vaccine at least once from 2004-2015. Adjusted estimates showed lower odds for respiratory illness in immunized children with prior inactivated influenza vaccine compared to children immunized for the first time.
Implications
- These findings suggest that there is residual protection from earlier inactivated influenza vaccinations. This is particularly relevant for children with pre-existing medical conditions who receive inactivated influenza vaccines repeatedly during childhood.
