Tweet
Clin Infect Dis. 2017 Mar 21. doi: 10.1093/cid/cix241. [Epub ahead of print]
Contribution of serology assays in the evaluation of influenza virus infection rates and vaccine efficacy in pregnant women: Report from randomized controlled trials.
Madhi SA1,2,3, Nunes M1,2, Weinberg A4, Kuwanda L1,2, Hugo A1,2, Jones S1,2, van Niekerk N1,2, Ortiz JR5, Neuzil KM6, Klugman KP7, Simoes EA8, Cutland CL1,2; Matflu team.
Author information
Abstract
Background:
The utility of serological testing to evaluate vaccine efficacy of seasonal inactivated influenza vaccine (IIV) is controversial. We aimed to evaluate the efficacy of IIV against serologically-diagnosed influenza infection (SDI), and reverse-transcription polymerase chain reaction confirmed influenza illness (PCR-CI) in women vaccinated during pregnancy.
Methods:
We undertook a post-hoc analysis of two randomized clinical trials evaluating IIV efficacy among HIV-uninfected and HIV-infected pregnant women. SDI was defined as ≥4-fold increase in paired hemagglutinin antibody inhibition (HAI) titres from one month post-vaccination until end-of-study participation. PCR-CI was defined as molecular diagnostic evidence of influenza virus in pharyngeal specimens collected during clinical illness.
Results:
Among placebo-recipients, the respective incidence of PCR-CI and SDI were 5.6% and 35.0% in HIV-uninfected women; and 20.5% and 43.6% among HIV-infected women. Vaccine efficacy in HIV-uninfected women was similar for PCR-CI (66.9%; 95%CI: -20.1 to 90.9) and SDI (59.2%; 95%CI: 37.0 to 73.5), however, fewer women required vaccination to prevent one episode of SDI (5; 95%CI: 3 to 9) than PCR-CI (27; 95%CI: 12 to ∞). Also, vaccine efficacy was similar for PCR-CI (61.2%; 95%CI: 10.7 to 83.2) and SDI (60.9%; 95%CI: 3.9 to 76.9) in HIV-infected women, with 2-fold fewer women needing to be vaccinated to prevent SDI (4; 95%CI: 3 to 8) than PCR-CI (8; 95%CI: 4 to 52).
Conclusion:
Although vaccine efficacy was similar when measured for PCR-CI or SDI, IIV vaccination prevented a greater number of SDI than PCR-CI, the clinical relevance of the former warrants interrogation.
KEYWORDS:
efficacy; hemagglutination inhibition assay; immunogenicity; influenza vaccine; phase III trial
PMID: 28369198 DOI: 10.1093/cid/cix241
Contribution of serology assays in the evaluation of influenza virus infection rates and vaccine efficacy in pregnant women: Report from randomized controlled trials.
Madhi SA1,2,3, Nunes M1,2, Weinberg A4, Kuwanda L1,2, Hugo A1,2, Jones S1,2, van Niekerk N1,2, Ortiz JR5, Neuzil KM6, Klugman KP7, Simoes EA8, Cutland CL1,2; Matflu team.
Author information
Abstract
Background:
The utility of serological testing to evaluate vaccine efficacy of seasonal inactivated influenza vaccine (IIV) is controversial. We aimed to evaluate the efficacy of IIV against serologically-diagnosed influenza infection (SDI), and reverse-transcription polymerase chain reaction confirmed influenza illness (PCR-CI) in women vaccinated during pregnancy.
Methods:
We undertook a post-hoc analysis of two randomized clinical trials evaluating IIV efficacy among HIV-uninfected and HIV-infected pregnant women. SDI was defined as ≥4-fold increase in paired hemagglutinin antibody inhibition (HAI) titres from one month post-vaccination until end-of-study participation. PCR-CI was defined as molecular diagnostic evidence of influenza virus in pharyngeal specimens collected during clinical illness.
Results:
Among placebo-recipients, the respective incidence of PCR-CI and SDI were 5.6% and 35.0% in HIV-uninfected women; and 20.5% and 43.6% among HIV-infected women. Vaccine efficacy in HIV-uninfected women was similar for PCR-CI (66.9%; 95%CI: -20.1 to 90.9) and SDI (59.2%; 95%CI: 37.0 to 73.5), however, fewer women required vaccination to prevent one episode of SDI (5; 95%CI: 3 to 9) than PCR-CI (27; 95%CI: 12 to ∞). Also, vaccine efficacy was similar for PCR-CI (61.2%; 95%CI: 10.7 to 83.2) and SDI (60.9%; 95%CI: 3.9 to 76.9) in HIV-infected women, with 2-fold fewer women needing to be vaccinated to prevent SDI (4; 95%CI: 3 to 8) than PCR-CI (8; 95%CI: 4 to 52).
Conclusion:
Although vaccine efficacy was similar when measured for PCR-CI or SDI, IIV vaccination prevented a greater number of SDI than PCR-CI, the clinical relevance of the former warrants interrogation.
KEYWORDS:
efficacy; hemagglutination inhibition assay; immunogenicity; influenza vaccine; phase III trial
PMID: 28369198 DOI: 10.1093/cid/cix241