Determination and Evaluation of Potency of Thermostable 1-2 Vaccine after Long-Term Storage by Using Conventional and Rapid Potency Tests

Abstract

Study was conducted to determine and evaluate the potency of 1-2 vaccine after a long-term (11 months) storage prior to the running of ND vaccination campaign in village chickens in Central and Southern Tanzania. Both rapid and conventional tests were employed to determine potency of 1-2 vaccine. By using a rapid test the results were obtained within 12 hours and indicated that the titre of the vaccine was below the recommended titre of c!: 10 6 EID₅₀/0.1 mL thus unsatisfactory for use in the field. When a conventional 4-day test was used vaccines from Dodoma, Mpwapwa and Mtwara had titres of 5.5, 4.8 and 5.6 EID₅₀/0.1 mL, respectively proving further that the rapid test was accurate. Although 1-2 vaccine is thermostable it should be transported and stored in a cool environment (less dependent on cold chain) to extend its shelf life and hence its potency. This is the first report of using a rapid potency test to determine and evaluate the potency of 1-2 vaccine in the field. Therefore continuous monitoring and assessment of conditions of storage and potency testing would contribute towards good ND vaccine strategy and vaccination campaigns.