Vaccination Compliance: Are standard delivery doses non-standard doses?

Modern pig farming requires to set up adequate vaccination programs to prevent or decrease economic loss from important infectious diseases. Vaccination compliance is a key success factor for a cost-effective prevention strategy. It relies on the administration of the correct dosage, by the correct route at the correct date. During the vaccination process, leakage or bleeding out of vaccine droplets may be observed on the pig skin surface, particularly when using conventional vaccination material. Even when obtaining the expected efficacy results, the observation by the operator of this may affect the psychological sensation that pigs are appropriately vaccinated. The objective of this study was to evaluate the quantity of vaccine on the skin of pigs following a standard intramuscular injection in the neck.

Sixteen piglets, 4 per weight category i.e. 4-5 kg, 6-7 kg, 8-10 kg and 15-20 kg, were randomly selected in a commercial farm. No vaccine had been injected in the neck before the study day. Following cleaning and drying of the skin surface, 0.5-mL of CIRCOVAC® (Merial, Lyon, France), was injected, IM in the neck, according to the manufacturer instructions. Before injection a piece of blotting paper (4cm², 90g/m²) in an empty screw cap tube was weighed using a qualified precision scale. Just after injection, the piece of paper was applied on the skin surface at the injection site for 2 seconds then immediately stored in the screw cap container and the tube was then weighed. The quantity of vaccine lost on the skin surface was calculated by difference. The visible collection of any trace of blood, another other body fluid or exogenous water on the blotting paper led to the exclusion of the observation.

On average, the volume of vaccine lost on the skin was 1.28% ± 0.85% of the standard dose (n=14), ranging from 0.20% to 3.45%. The average percentage per dose remaining on the skin surface were 1.67%, 1.27%, 0.88% and 1.15% for pigs vaccinated with 0.5 mL of CIRCOVAC and weighing 4-5 kg, 6-7 kg, 8-10 kg and 15-20 kg respectively, indicating the absence of age-dependency for the observation of this phenomenon.

Under the conditions of the study, the volume of a vaccine present on the skin of a pig following a standard intramuscular injection in the neck was 1.28% of the administered dose, what was considered as acceptable. Vaccination compliance was thought not to be impacted as vaccines doses are planned to accommodate this variation in delivery dose.

Disclosure of Interest: S. Paranese: None Declared, G. Leotti Conflict with: Merial Italia SpA, G. Sarli: None Declared.