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Efficacy of a single dose of live attenuated influenza vaccine in previously unvaccinated children: a post hoc analysis of three studies of children aged 2 to 6 years.
Clin Ther. 2009 Oct; 31(10):2140-7.CT

Abstract

BACKGROUND

Although 2 doses of influenza vaccine are recommended for children aged <9 years who have not been previously vaccinated, children may receive only 1 dose because of suboptimal adherence to national influenza vaccination recommendations.

OBJECTIVE

This study evaluated the efficacy and tolerability of a single dose of the live attenuated influenza vaccine (LAIV) in previously unvaccinated children aged > or = 2 years, the population for which LAIV is approved.

METHODS

This study was a post hoc subgroup analysis of previously published studies. Three randomized, double-blind, placebo-controlled clinical trials have evaluated the efficacy of a single dose of LAIV in previously unvaccinated young children. Single-dose efficacy, as a prespecified outcome, was evaluated in the subgroup of children aged 2 to 6 years. Reactogenicity and adverse events through 10 days after vaccination were reported after 1 and 2 doses.

RESULTS

Across all studies combined, the mean (SD) ages of the children within the subgroups analyzed were 35.8 (12.1) months for LAIV recipients and 34.5 (11.3) months for placebo recipients. The groups were balanced by sex, with 51% and 50% boys in the LAIV and placebo groups, respectively. The LAIV and placebo groups were also balanced with regard to the countries of origin, as follows: United States (35% LAIV, 31% placebo), Southeast Asia (35% LAIV, 44% placebo), South America (19% LAIV, 15% placebo), and South Africa (11% LAIV, 11% placebo). In a post hoc subgroup analysis of children aged 2 to 6 years from these 3 studies, the efficacy of a single dose of LAIV compared with placebo was 71.5% (95% CI, 52.9% to 83.4%), 87.3% (95% CI, 59.2% to 96.1%), and 59.9% (95% CI, 31.1% to 77.4%). Two of the studies compared the efficacy of 1 and 2 doses of vaccine in the same season. The 1-dose efficacy of LAIV was 87% to 92% of the 2-dose efficacy. Upon revaccination in year 2 with a single dose, year-2 efficacy was not significantly different for children who received either 1 or 2 doses in year 1 (1 dose in year 1, efficacy 64.1% [95% CI, 13.1% to 85.7%]; 2 doses in year 1, efficacy 55.4% [95% CI, -23.6% to 85.9%]; P = NS). All reactogenicity events associated with the first dose of LAIV were decreased after the second dose, with the exception of cough.

CONCLUSIONS

A single dose of LAIV provided significant but not optimal protection against influenza in previously unvaccinated children. This finding may be of particular importance for children who are at risk of being partially immunized.

Authors+Show Affiliations

Kentucky Pediatric and Adult Research, Bardstown, Kentucky 40004-1142, USA. slblock@pol.netNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Multicenter Study
Randomized Controlled Trial

Language

eng

PubMed ID

19922885

Citation

Block, Stan L., et al. "Efficacy of a Single Dose of Live Attenuated Influenza Vaccine in Previously Unvaccinated Children: a Post Hoc Analysis of Three Studies of Children Aged 2 to 6 Years." Clinical Therapeutics, vol. 31, no. 10, 2009, pp. 2140-7.
Block SL, Toback SL, Yi T, et al. Efficacy of a single dose of live attenuated influenza vaccine in previously unvaccinated children: a post hoc analysis of three studies of children aged 2 to 6 years. Clin Ther. 2009;31(10):2140-7.
Block, S. L., Toback, S. L., Yi, T., & Ambrose, C. S. (2009). Efficacy of a single dose of live attenuated influenza vaccine in previously unvaccinated children: a post hoc analysis of three studies of children aged 2 to 6 years. Clinical Therapeutics, 31(10), 2140-7. https://doi.org/10.1016/j.clinthera.2009.09.014
Block SL, et al. Efficacy of a Single Dose of Live Attenuated Influenza Vaccine in Previously Unvaccinated Children: a Post Hoc Analysis of Three Studies of Children Aged 2 to 6 Years. Clin Ther. 2009;31(10):2140-7. PubMed PMID: 19922885.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Efficacy of a single dose of live attenuated influenza vaccine in previously unvaccinated children: a post hoc analysis of three studies of children aged 2 to 6 years. AU - Block,Stan L, AU - Toback,Seth L, AU - Yi,Tingting, AU - Ambrose,Christopher S, PY - 2009/08/26/accepted PY - 2009/11/20/entrez PY - 2009/11/20/pubmed PY - 2010/1/27/medline SP - 2140 EP - 7 JF - Clinical therapeutics JO - Clin Ther VL - 31 IS - 10 N2 - BACKGROUND: Although 2 doses of influenza vaccine are recommended for children aged <9 years who have not been previously vaccinated, children may receive only 1 dose because of suboptimal adherence to national influenza vaccination recommendations. OBJECTIVE: This study evaluated the efficacy and tolerability of a single dose of the live attenuated influenza vaccine (LAIV) in previously unvaccinated children aged > or = 2 years, the population for which LAIV is approved. METHODS: This study was a post hoc subgroup analysis of previously published studies. Three randomized, double-blind, placebo-controlled clinical trials have evaluated the efficacy of a single dose of LAIV in previously unvaccinated young children. Single-dose efficacy, as a prespecified outcome, was evaluated in the subgroup of children aged 2 to 6 years. Reactogenicity and adverse events through 10 days after vaccination were reported after 1 and 2 doses. RESULTS: Across all studies combined, the mean (SD) ages of the children within the subgroups analyzed were 35.8 (12.1) months for LAIV recipients and 34.5 (11.3) months for placebo recipients. The groups were balanced by sex, with 51% and 50% boys in the LAIV and placebo groups, respectively. The LAIV and placebo groups were also balanced with regard to the countries of origin, as follows: United States (35% LAIV, 31% placebo), Southeast Asia (35% LAIV, 44% placebo), South America (19% LAIV, 15% placebo), and South Africa (11% LAIV, 11% placebo). In a post hoc subgroup analysis of children aged 2 to 6 years from these 3 studies, the efficacy of a single dose of LAIV compared with placebo was 71.5% (95% CI, 52.9% to 83.4%), 87.3% (95% CI, 59.2% to 96.1%), and 59.9% (95% CI, 31.1% to 77.4%). Two of the studies compared the efficacy of 1 and 2 doses of vaccine in the same season. The 1-dose efficacy of LAIV was 87% to 92% of the 2-dose efficacy. Upon revaccination in year 2 with a single dose, year-2 efficacy was not significantly different for children who received either 1 or 2 doses in year 1 (1 dose in year 1, efficacy 64.1% [95% CI, 13.1% to 85.7%]; 2 doses in year 1, efficacy 55.4% [95% CI, -23.6% to 85.9%]; P = NS). All reactogenicity events associated with the first dose of LAIV were decreased after the second dose, with the exception of cough. CONCLUSIONS: A single dose of LAIV provided significant but not optimal protection against influenza in previously unvaccinated children. This finding may be of particular importance for children who are at risk of being partially immunized. SN - 1879-114X UR - https://www.unboundmedicine.com/medline/citation/19922885/Efficacy_of_a_single_dose_of_live_attenuated_influenza_vaccine_in_previously_unvaccinated_children:_a_post_hoc_analysis_of_three_studies_of_children_aged_2_to_6_years_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0149-2918(09)00343-9 DB - PRIME DP - Unbound Medicine ER -