In regard to the article appearing on page e170 of volume 30, issue 9, the study sponsor, GlaxoSmithKline Biologicals, has been recently investigating the quality of some serology assays used to determine the antibody titers reported in the publication.
The technical investigations of the following assays have now been completed and have led to the following findings:
Anti-Hepatitis B Surface Enzyme-Linked Immunosorbent Assay
A decrease in the specificity of this assay had been observed in some studies, and investigations have confirmed a poor assay performance for low levels of antibody titers (10–100 mIU/mL); in contrast, concentrations above 100 mIU/mL were confirmed valid.
The root cause was identified as the change of sourcing of a key assay reagent. The specificity of the in-house assay could not be restored, and therefore, testing was resumed using the commercial assay Centaur (ADVIA Centaur Immunoassay System, Siemens Healthcare Diagnostics), an Food and Drug Administration-approved and CE-marker chemiluminescence immunoassay with a cut-off defining seropositivity of 6.2 mIU/mL.
To generate corrected seroprotection rates, samples of this study that were originally tested in the range 10–100 mIU/mL have been retested using the commercial assay, within the limits of the serum volumes that remained available. Anti-hepatitis B surface (anti-HBs) seroprotection was redefined as in-house enzyme-linked immunosorbent assay concentration >100 mIU/mL or chemiluminescence immunoassay concentration >10 mIU/mL. Corrected seroprotection rates with 95% confidence intervals were calculated using multiple imputation method for subjects with in-house enzyme-linked immunosorbent assay titers between 10 and 100 mIU/mL.
The anti-HBs data resulting from this retesting differ from the published results, as shown in Table 1, and indicate that the study results with regard to the seroprotection rates for hepatitis B are impacted. The high seroprotection rates in children not receiving a hepatitis B vaccine was discussed as an unexpected finding in the original paper. This finding needs to be removed from the paper because seroprotection rates in these unvaccinated children are actually much lower and within the usual range.
Polio Neutralization Test
A trend toward lower anti- poliovirus titers was observed when testing was performed by an external contractor when compared with GlaxoSmithKline Biologicals’ internal laboratory.
The lower sensitivity of the assay performed by the contractor was mainly because of a change in the dilution of the poliovirus used in the challenge phase of the neutralization assay.
A clinical assessment was made to evaluate whether the trend for measuring lower anti-poliovirus neutralizing titers at our external contractor has impacted the conclusions relating to predefined immunogenicity clinical study objectives. Based on this assessment, it was concluded that the poliovirus immunogenicity conclusions for all clinical studies tested at our external contractor were valid.
Furthermore, retesting of a panel of samples from different studies by an independent external reference laboratory confirmed the validity of the initial testing at our external contractor in terms of seroprotection rates.
As a result, GlaxoSmithKline Biologicals considers that the conservative estimates of anti-poliovirus titers tested at our external contractor have no impact on the results and conclusions of this study.
1. van den Bergh MR, Spijkerman J, François N, et al. Immunogenicity, safety and reactogenicity of the10-valent pneumococcal nontypeable Haemophilus influenzae
protein D conjugate vaccine and DTPa-IPV-Hib when coadministered as a three-dose primary vaccination schedule in the Netherlands: a randomized controlled trial. Pediatr Infect Dis J. 2011;30:e170–e178