Current Status of Live Attenuated Influenza Vaccine in the United States for Seasonal and Pandemic Influenza

Christopher S. Ambrose; Catherine Luke; Kathleen Coelingh

Disclosures

Influenza Resp Viruses. 2008;2(6):193-202. 

In This Article

Role of Antibody Responses to LAIV in Predicting Protection

It is important to note that, unlike TIV, no general immune correlates of protection have been established for LAIV. Serum antibody responses, mucosal antibody responses, and cellular responses have been observed in vaccine recipients; one study in young children demonstrated a correlation between interferon-gamma ELISPOT responses and protection from culture-confirmed influenza illness.[38] However, no similar correlation has been seen for serum antibody responses. Serum antibody responses are generally only detected in individuals with low titers of pre-existing serum antibody. Overall, studies have demonstrated that the proportion of individuals experiencing at least a fourfold rise in serum HA inhibition (HAI) antibody titer is often correlated with protective efficacy[11,18,39,40]; however, studies have also shown protection in the absence of significant antibody responses.[26,41] In the challenge study in healthy adults described above, LAIV provided 85% protection against influenza illness despite the fact that only 24% of LAIV recipients experienced a = 4-fold rise in HAI titer following vaccination. Interestingly, this study also suggested that serologic endpoints in influenza vaccine efficacy trials may underestimate influenza infections in TIV recipients (thus overestimating efficacy) because none of the four TIV recipients who developed influenza illness after wild-type challenge experienced a = 4-fold rise in HAI titer with illness (pre-challenge, post-vaccination titers were < 4, 32, 128, and 128).

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