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Withdrawal study supports USDA safety approval, 21-day withdrawal (SQ, IM)

ENABL adjuvants are regulatory-ready for use in cattle vaccines administered subcutaneously and intramuscularly. Based on this study and other research, USDA approved the safety of five cattle formulations with a 21-day withdrawal period — the shortest allowed by USDA and an especially important feature when developing vaccines for practical use.

 

                  Withdrawal study in cattle (SQ, IM)

Treatment

Products

Route

Dose

No. of Animals

Day

1

KIlled K99 (E coli) + ENABL

IM, right neck

2 mL

5

21

Killed K99 + phosphate-buffered saline (PBS)

IM, left neck

2

Killed K99 + ENABL

IM, left neck

2 mL

5

21

Killed K99 + PBS

IM, right neck

3

Killed K99 + ENABL

SQ, right neck

2 mL

5

21

Killed K99 + PBS

SQ, left neck

4

Killed K99 + ENABL

SQ, left neck

2 mL

5

21

Killed K99 + PBS

SQ, right neck

 

  • 11 animals had nodules at 15 injection sites (10 at adjuvant site; 5 at placebo site); all but 1 cleared at Day 21
  • At necropsy, 6 sites with gross lesions: 4 at adjuvant SQ sites; 2 at placebo sites
  • Respiratory pneumonia became evident during study; all were treated with antibiotics
  • 1 death not attributable to inoculation at Day 3; 5 animals with elevated temperatures
  • By histology exam, skin and muscle (76 possible scores)
    • 65 normal
    • 7 scores (1 IM, 5 SQ) from adjuvant, rest from placebo
    • Part of the infiltration at the scored sites were typical of acute immune response recruitment; others were trauma due to physical damage