STABILITY AND STERILITY STUDIES ON THE ROUTINE IMMUNIZATION VACCINES IN USE IN SOUTH-EAST NIGERIA

Abstract

Objectives: The study sets to evaluate the stability and sterility of the vaccines used in the routine immunization programme in the five states of the south-east geo-political zone of Nigeria (Abia, Anambra, Ebonyi, Enugu and Imo States). Methods: The stability studies carried out include: thermal stability test by colony count for the Bacillus Calmette-Guérin (BCG) Vaccines, physical examinations on all the vaccines and shake test on the Diphtheria-Tetanus-Pertussis (DPT), Hepatitis B and Pentavalent vaccines. Test for sterility was carried out using tests for bacteria and fungi contamination. The bacteria endotoxin quantification test (Limulus Amebocyte Lysate test) was also done to test for the presence or absence of pyrogens/endotoxins. Key findings: The BCG vaccines have mean percentage potency losses of 13.67±4.45 > 12.99±5.15 > 12.44±4.36 > 12.05±4.98 > 10.71±6.62 for from Anambra, Abia, Enugu, Imo and Ebonyi respectively. The shake test showed that the adsorbed vaccines (DPT, Hepatitis B and Pentavalent) had no granules or floccules. The vaccines’ mean settling times were 25.33 ±2.52, 20.60 ±2.07 and 25.50 ±0.71 minutes for DPT, Hepatitis B and Pentavalent vaccines used as control respectively and 72.00±17.32, 63.20±12.28, 63.50±2.12 minutes for the vaccine samples respectively. On physical examination, none of the vaccines had any visible change in appearance. The Limulus Amebocyte Lysate (LAL) test did not detect any bacteria endotoxin in the viral vaccine except in the bacteria vaccines (BCG and DPT). However, the endotoxin concentration was within the Pharmacopeias limit for vaccines and biological products. The tests for bacteria and fungi contamination did not reveal any contaminant. Conclusions: The vaccines showed good and acceptable sterility and stability profiles.