Moreover, before the enrollment, at 15
days of age, the animals were bled and serologically tested
for negativity to M. hyopneumoniae antibodies by using a
IDEXX M. hyo. commercial test kit (S/P ratio < 0.4). Upon
arrival, the animals were randomly allocated to four
different groups (10 piglets each) and individually
identified by a numbered ear tag. At 28 days of age, the
piglets were injected as follows: Group A = intradermal
(ID) administration of a commercial vaccine [Porcilis1 M.
hyo. ID ONCE – MSD AH (formerly Intervet International),
Boxmeer, The Netherlands] by using the needle-less IDAL1
vaccinator at a dose of 0.2 ml (vaccine A); Group
B = intramuscular administration of a commercially available
vaccine (vaccine B); Group C = intramuscular administration
of the adjuvant only (2 ml of X-solve, the adjuvant
of vaccine A); Group D = intramuscular administration of a
commercially available vaccine (vaccine D). The dose of the
vaccines B and D is intentionally omitted in order to avoid
any possibility to identify the commercially available
products. All vaccines administered in this study were
licensed as a one dose