Antibody responses to vaccination with WRL 105 strain live influenza vaccine in previously vaccinated and unvaccinated volunteers

Abstract

Intranasal vaccination with a single 0.5 ml dose of 10(7.0) EID 50 WRL 105 strain live influenza vaccine elicited four-fold or greater increases in circulating homotypic haemagglutinating inhibiting (HAI) antibody in 60 (64.5%) of 93 volunteers, or in 58 (74.4%) of 78 volunteers with HAI antibody titres before vaccination of less than or equal to 1/20. In comparison, in a group of volunteers vaccinated 9 months previously re-vaccination elicited antibody responses in only 4 (6.9%) of 58 volunteers, or in 3 (14.3%) of 21 volunteers with antibody titres before vaccination of less than or equal to 1/20. Titres of vaccine-induced antibody and antibody resulting from earlier natural infection appeared to fall slowly and at equivalent rates over a 9 month period.

Correlation of Cellular Immune Responses with Protection against Culture-Confirmed Influenza Virus in Young Children

“…It has been observed previously that responses elicited by LAIV, but not TIV, were inversely proportional to prevaccination levels of influenza virus-specific antibody for all age groups, suggesting a strong role of previous exposure to the antigen in eliciting IFN-␥ responses upon reexposure (23,31,43,53). One notable exception was that in a previous report, children aged 6 months to Ͻ5 years, with little evidence of previous exposure, were most responsive to TIV (31).…”

Pathogenicity of influenza virus.

“…Inevitably, most trials must be conducted with relatively few heathly adult volunteers of variable antibody status. They can be misleading (36,61), especially about the virulence of strains for the old and young. Hence, such trials should not form the immutable basis against which all other assessments of virulence are judged.…”