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Comparison of monovalent and trivalent live attenuated influenza vaccines in young children
W C Gruber1, K Kirschner, S Tollefson
1Dept. of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232-2581.
Insights
Intranasal influenza vaccines (ca) containing live, attenuated viruses were safe and effective in young children. Trivalent formulations induced robust immune responses against H1N1 and H3N2, and an increased dose of B strain improved protection.
Area of Science:
- Virology
- Immunology
- Pediatrics
Background:
- Influenza remains a significant public health concern in young children.
- Live, attenuated cold-adapted (ca) influenza virus vaccines offer a promising alternative to inactivated vaccines.
- Previous studies have explored the safety and immunogenicity of ca influenza vaccines in pediatric populations.
Purpose of the Study:
- To evaluate the safety and immunogenicity of a trivalent intranasal live, attenuated, cold-adapted (ca) influenza vaccine in children aged 6 months to 2 years.
- To assess the impact of different dosage levels of the B strain on vaccine response.
- To compare the efficacy of trivalent versus monovalent vaccine formulations.
Main Methods:
- A randomized, placebo-controlled trial involving 50 children vaccinated intranasally with a trivalent ca influenza vaccine.
- Vaccine contained H1N1, H3N2, and B strains at varying doses (10^6 TCID50 for H1N1/H3N2; 10^4 or 10^6 TCID50 for B).
- Monovalent vaccines and placebo were administered to control groups; adverse reactions and infection rates were monitored.
Main Results:
- No clinically significant adverse reactions were observed in any vaccine group.
- Over 90% of seronegative children were infected by H1N1 and H3N2 vaccine strains.
- A 10^6 TCID50 dose of the B strain in the trivalent vaccine achieved an 81% infection rate, significantly higher than the 27% rate with a 10^4 TCID50 dose.
Conclusions:
- Trivalent ca influenza vaccines are safe and immunogenic in young children.
- The dose of the B strain is critical for achieving adequate infection rates.
- Intranasal ca influenza vaccines represent a viable strategy for pediatric influenza prevention.
Abstract:
Fifty children, 6 months to 2 years of age, were vaccinated intranasally with a trivalent preparation containing 10(6) TCID50 each of H1N1 and H3N2 and 10(4) (n = 14) or 10(6) (n = 36) TCID50 of B live, attenuated, cold-adapted (ca) influenza strains. The same doses were administered as monovalent vaccines to 69 comparably aged children. Forty-five controls were given placebo. No clinically significant adverse reactions to vaccines were observed. Of children seronegative to H1N1 or H3N2, > or = 90% were infected by these vaccine strains. Trivalent vaccine containing 10(4) TCID50 of B infected only 27% of children seronegative to B (3/11), which was markedly reduced from the 88% infection rate (7/8) following monovalent B vaccine of the same dose (P = .02); increasing the B dose to 10(6) TCID50 increased the infection rate to 81% (21/26). Replication of ca influenza viruses in tissue culture matched vaccine responses. Trivalent ca influenza vaccines can be formulated that are safe and immunogenic in young children.