The required sample size in vaccination-challenge experiments with infectious bronchitis virus, a meta-analysis

Area of Science:

• Veterinary Immunology
• Experimental Design
• Poultry Health

Background:

• Accurate experimental design in poultry research, particularly for infectious bronchitis virus (IBV) studies, requires careful consideration of group sizes.
• Statistical, animal welfare, and financial factors necessitate precise estimation of the number of chickens per group and tracheal organ cultures (TOCs) per chicken.
• Key parameters influencing sample size include the desired detectable difference in protection (effect size), variability, confidence level, and statistical power.

Purpose of the Study:

• To perform a meta-analysis of existing IBV vaccination-challenge experiments.
• To determine and quantify sources of variation in protection levels across different experimental groups.
• To provide data for estimating the optimal number of chickens per group for future IBV research.

Main Methods:

• A meta-analysis was conducted on data from 18 IBV vaccination-challenge experiments.
• 137 chicken groups were clustered based on age, vaccination type, challenge type, and vaccination location.
• Sample size calculations were performed for various effect sizes (6.25% to 50%) using 2, 5, or 10 TOCs per chicken, with 95% confidence and 80% power.

Main Results:

• The meta-analysis identified key sources of variation in protection levels.
• Estimated group sizes required to detect specified effect sizes varied significantly, ranging from 2 to 650 chickens.
• The number of TOCs per chicken also influenced the required sample size.

Conclusions:

• This study provides essential data for researchers to estimate appropriate chicken group sizes in IBV vaccination-challenge studies.
• The findings enable more reliable and statistically sound experimental designs, considering specific vaccination and challenge strains.
• Optimizing group size contributes to improved animal welfare and efficient resource allocation in poultry research.