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Trivalent inactivated influenza virus vaccine given to two-month-old children: an off-season pilot study
Emmanuel B Walter1, Janet A Englund, Mark Blatter
1Department of Pediatrics, Duke University Medical Center, Durham, NC, USA. walte002@mc.duke.edu
Insights
Trivalent inactivated influenza vaccine (TIV) is safe for infants 6 to 12 weeks and 6 months old. Antibody response was lower in younger infants, likely due to maternal antibodies.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Immunology
Background:
- Infants under 6 months have the highest risk of influenza hospitalization.
- Current influenza vaccines are not approved for children younger than 6 months.
Purpose of the Study:
- To assess the safety and immunogenicity of the 2004-2005 trivalent inactivated influenza vaccine (TIV) in infants.
- To evaluate TIV administration in two age groups: 6 to 12 weeks and 6 months.
Main Methods:
- An open-label, off-season study involving healthy infants.
- Two doses of TIV administered 1 month apart, alongside routine pediatric vaccines.
- Safety assessed via parental diaries; immunogenicity analyzed through serum antibody titers.
Main Results:
- TIV was well-tolerated, with generally mild injection site reactions and fevers resolving within 3 days.
- Postvaccination seroprotection rates varied by age and influenza strain, with higher rates in 6-month-olds.
- In 6- to 12-week-olds without pre-existing antibodies, responses to influenza A antigens approached those of 6-month-olds.
Conclusions:
- Trivalent inactivated influenza vaccine (TIV) is safe and well-tolerated in infants aged 6 to 12 weeks and 6 months.
- Lower antibody response in younger infants may be attributed to passively acquired maternal antibodies.
- Infants 6 to 12 weeks old without prior antibodies showed promising responses to influenza A antigens.
Background:
Although children less than 6 months of age have the highest risk for hospitalization related to influenza infection, influenza vaccine is not approved for these children.
Methods:
In an open-label, off-season study, healthy 6 to 12 week and 6-month-old children received 2 doses of the 2004 to 2005 trivalent inactivated influenza vaccine (TIV) administered 1 month apart along with other routine pediatric vaccines. Safety was assessed by parental diaries (n = 393). Immunogenicity analyses (n = 293) were performed on sera obtained before vaccination and 1 month after the second dose of TIV. Outcomes included the frequencies of subjects with injection site and systemic reactions and seroprotection rates to TIV antigens.
Results:
Injection site reactions and fevers were generally mild and resolved within 3 days. Postvaccination seroprotection rates (titer > or = 1:40) in the 6- to 12-week-old and 6-month-old groups were 46% and 69% to A/New Caledonia (H1N1), 59% and 79% to A/Wyoming (H3N2), and 5% and 22% to B/Jiangsu (P < 0.001, all comparisons). For seronegative 6- to 12-week-olds whose mothers had not received TIV during pregnancy, postvaccination seroprotective titers to A/New Caledonia (H1N1) were achieved in 70% (38/54) and to A/Wyoming (H3N2) in 68% (23/34) of infants.
Conclusions:
TIV was well tolerated and safe when administered to children at both 6 to 12 weeks and 6 months of age. The antibody response was lower in the younger children, probably related to antibody suppression from passively acquired antibodies from mothers. In 6- to 12-week-olds without preexisting antibody, seroresponses to influenza A antigens approached those of 6-month-old children.
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