Using physical method to determine the previous freezing of absorbed DTP vaccine

ABSTRACT

Absorbed DTP vaccines in the same Lot (produced by IVAC, Nha Trang) were kept at 4°C, -5 +/-10oC, -20°C on 2, 3 and 6 hours. After being thawed completely, the vaccine containers were vigorously shaken and the contents were examined for physical changes. The results showed that the containers kept at 4oC had no physical changes; the containers kept at -5 +/-10oC, 20°C for 6 hours had significant changes such as agglomeration, floccules or granular matter, and sedimented rapidly. It is suggested that structure of aluminum adjuvant in DTP vaccine is changed. The containers kept at -5 +/-10oC, -20°C for 6 hours can be considered as the positive control and the shaking test can be used to determine the previous freezing of adsorbed DTP vaccines.