Lot Consistency as an Equivalence Problem

Phase III, randomized controlled trial in girls 9-15 years old to evaluate lot consistency of a novel nine-valent human papillomavirus L1 virus-like particle vaccine

A 9-valent human papillomavirus (6/11/16/18/31/33/45/52/58) VLP (9vHPV) vaccine has recently been proven highly efficacious in preventing disease associated with vaccine HPV types in a pivotal Phase III study. The demonstration of lot-to-lot consistency to confirm the reliability of the manufacturing process is a regulatory requirement for vaccine licensure in the United States. A randomized trial was conducted to demonstrate that three lots of 9vHPV vaccine elicit equivalent antibody response for all 9 vaccine types. The study required thorough planning because it required success on 27 separate statistical comparisons. An innovative statistical approach was used taking into account between-lot variance for more conservative power calculations. The study demonstrated equivalence of three lots of 9vHPV vaccine for all 9 vaccine types.

Assessing consistent treatment effect in a multi-regional clinical trial: a systematic review

A key issue in multi-regional clinical trials (MRCTs) is how to assess the consistency of treatment effect across regions, although there is no a priori reason to believe that the treatment effect should vary across the regions. In this article, we define the research question as an assessment of overall consistency across all regions for which all regions are considered equally important. This is different from the region/country-specific analyses (e.g. US vs Non-US), which are frequently requested by local regulatory agencies and usually performed for multiple agencies. We provide a systematic review of methods that may potentially be used for assessing consistency across regions, including commonly used quantitative/qualitative interaction tests, Japanese Pharmaceutical Medical Device Agency (PMDA) Methods 1 & 2, and those proposed for different purposes (e.g. bridging studies, meta-analysis, and vaccine lot consistency, among others). These methods are classified into three groups: global methods, multivariate quantitative methods, and multivariate qualitative methods. A case study is used to illustrate these methods. We also provide recommendations on how to choose appropriate methods and incorporate them in the study design.

On the relationship between mean antibody level, seroprotection and clinical protection from influenza

For many vaccines the amount of antibodies induced has a positive correlation with the likelihood of clinical protection from disease. Mean antibody level is therefore frequently used as a serological surrogate endpoint for vaccine efficacy. In addition, a dichotomous surrogate endpoint is often defined: seroprotection. We explore the relationship between mean antibody level, seroprotection and clinical protection from influenza, using a simple statistical model. The model reveals that the relationship depends not only on the mean but also on the dispersion of the antibody levels, the threshold for clinical protection and the clinical protection curve. The consequences for the interpretation of mean antibody levels and seroprotection rates in terms of clinical protection from influenza are discussed.

Sample size for equivalence trials: a case study from a vaccine lot consistency trial

For some trials, simple but subtle assumptions can have a profound impact on the size of the trial. A case in point is a vaccine lot consistency (or equivalence) trial. Standard sample size formulas used for designing lot consistency trials rely on only one component of variation, namely, the variation in antibody titers within lots. The other component, the variation in the means of titers between lots, is assumed to be equal to zero. In reality, some amount of variation between lots, however small, will be present even under the best manufacturing practices. Using data from a published lot consistency trial, we demonstrate that when the between-lot variation is only 0.5 per cent of the total variation, the increase in the sample size is nearly 300 per cent when compared with the size assuming that the lots are identical. The increase in the sample size is so pronounced that in order to maintain power one is led to consider a less stringent criterion for demonstration of lot consistency. The appropriate sample size formula that is a function of both components of variation is provided. We also discuss the increase in the sample size due to correlated comparisons arising from three pairs of lots as a function of the between-lot variance.

Statistical Analysis of Influenza Vaccine Lot Consistency Studies

This paper presents an integrated statistical approach to the analysis of influenza vaccine lot consistency studies in which three lots are compared. The approach ensures that the overall Type I error rate (i.e., the probability of wrongly concluding that the lots are similar) is controlled. It is argued that the optimum efficacy measure is the geometric mean titer. The approach is demonstrated using data from a randomized, double-blind lot consistency study in which three consecutive production lots of Solvay Pharmaceuticals' new, virosomal subunit influenza vaccine Invivac were compared.