Influenza Vaccination of Children: Old and New Challenges
Influenza Vaccination of Children: Old and New Challenges
Abstract & Commentary
By Hal B. Jenson, MD, Chair, Department of Pediatrics; Director, Center for Pediatric Research, Eastern Virginia Medical School and Children's Hospital of the King's Daughter, is Associate Editor for Infectious Disease Alert.
Dr. Jenson is on the speaker's bureau for Merck.
Synopsis: The safety and immunogenicity of one versus 2 doses of trivalent influenza vaccine was evaluated in children 5-8 years of age. Seronegative children required 2 doses, whereas seropositive children required only one dose, but there was no clinical or demographic discriminator that predicted serostatus. Because serologic testing is impractical, all unvaccinated children < 9 years of age should continue to receive 2 doses of influenza vaccine.
Source: Neuzil KM, et al. Immunogenicity and reactogenicity of 1 versus 2 doses of trivalent inactivated influenza vaccine in vaccine-naive 5 8-year-old children. J Infect Dis. 2006;194:1032-1039.
A prospective study of the immunogenicity and reactogenicity of one vs 2 doses of 2004-2005 trivalent influenza vaccine (TIV), in 5 8-year-old children, was conducted among 280 children who had not received TIV. Of these, 222 received 2 doses of TIV and had 3 blood samples. An additional 10 received 2 doses of TIV and were included in the safety analyses. The mean age of the 222 children was 6.5 years; 57% were male. The proportion of seropositive (HAI titer > 1:10) children before immunization was 54% for A/H1N1, 91% for A/H3N2, and 30% for B vaccine antigens; vaccine response among seropositive children after only one dose was 95%, 100%, and 100%, respectively, with high geometric mean titers (GMTs). Antibody responses among seronegative children were low after one dose, and were significantly greater after 2 doses (P < 0.001 for A/H1N1; P = 0.01 for A/H3N2; P < 0.001 for B), with significantly higher GMTs. Adjusting for baseline titer, neither age nor sex was predictive of protective antibody response after only one dose. Interestingly, seropositive children had higher GMTs after one dose than did seronegative children after 2 doses, indicating that priming with natural infection is superior to TIV. Vaccine responses and GMTs were significantly lower for the B component than for the A components.
Vaccination was very well tolerated. Fever during the 5-day observation period occurred in < 1% of children. Only the incidence of pain was significantly higher after dose 2 (P = 0.002 for any pain; P < 0.001 for moderate/severe pain), primarily among older (7-8 years of age) children. Prevaccination antibody titer > 1:10 was predictive of moderate/severe pain after 2 doses (relative risk, 1.60 [95% confidence interval, 1.01-2.56]). No child had pain after 3 days.
Commentary
The immunogenicity of the modern TIV has not previously been evaluated in children, but was based on studies of monovalent or bivalent vaccines. These results affirm the current recommendations of the Advisory Committee on Immunization Practices (ACIP) and American Academy of Pediatrics for 2 doses (> 4 weeks apart) of TIV in children < 9 years of age receiving TIV for the first time. Although seropositive children had a satisfactory response after only one dose, there were no clinical or demographic parameters in the distinguished seropositive children, and serologic testing prior to initial immunization is impractical.
From 15-30% of school-aged children acquire influenza each year, and serve as important vectors for intrafamilial transmission. In 2002, the ACIP encouraged the use of TIV among children 6-23 months of age, followed by expanded ACIP recommendations, beginning with this influenza season, to immunize all children < 5 years of age with TIV. The implementation of the recommendation for TIV use among children has lagged. In 2003-2004, immunization rates for children 6-23 months of age were calculated as 17.5% for one dose and 8.4% for 2 doses.
The 2-dose regimen for vaccine-naive children remains the best strategy to prevent influenza among young children. As younger children are increasingly immunized with TIV, fewer older children will require 2 doses of vaccine. This will diminish even further the very low rates of adverse effects associated with TIV, which is primarily pain after the second dose of TIV among older children.
A prospective study of the immunogenicity and reactogenicity of one vs 2 doses of 2004-2005 trivalent influenza vaccine (TIV), in 5 8-year-old children, was conducted among 280 children who had not received TIV. Of these, 222 received 2 doses of TIV and had 3 blood samples. An additional 10 received 2 doses of TIV and were included in the safety analyses. The mean age of the 222 children was 6.5 years; 57% were male.Subscribe Now for Access
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