EVALUATION OF POTENCY OF RabiES VACCINE PRODUCED IN PASTEUR INSTITUTE OF HOCHIMINH CITY BY NIH TEST

Nguyen Kim Dung, Nguyen Thi Ngoc Nhi

QC Laboratory

Using 3 to 4 vaccine dilutions and the parallel reference vaccine makes NIH test is more valuable than Habel test in testing potency of rabies vaccine.

To contribute in setting-up potency criteria of SMB rabies vaccine nationwide tested by NIH method, checking the potency of SMB rabies vaccine produced at Pasteur Institute HCMC by this method were performed.

15 lots of rabies vaccine were checked the potency by parallel Habel test to NIH test.

The results showed that:

– According to Habel test: 15/15 lots met the criteria in which the Preventive LD50 should be more than 10³ with the Geometric Mean of 10 ^{3.96 ± 0.54}

– Meantime, following NIH test: With challenge dose of 23 – 73 LD50, ED50 (log10) (GM) were of 1.73; 1.75 and 1.73 calculating by Graphic, Reed-Muench (RM) and Angular Transformation methods respectively. When the potency was expressed in International Unit (IU), there were some destinies to these lots. If comparing directly 2 ED50 of tested and reference vaccines interpreted by RM method, there were 5/15 lots having the titer lower than the titer of reference vaccine (2IU /ml) and 3 of these 5 lots having the titer < 1.3IU/ml. However, if using the method of Angular Transformation and Analysis of Variance, there were only 2/15 lots having the titer lower than that of reference vaccine and lower than 1.3IU/ml.

– With challenge dose of 23 LD50, rabies vaccine produced at Pasteur Institute HCMC had the effect on mice higher than national reference vaccine. With the challenge dose of 73 LD50 the effects, of rabies vaccine HCMC and national reference rabies vaccine were the same.

– In the application of Angular Transformation and Analysis of Variance to verify the results from IN VIVO test like NIH, using appropriated dilutions depending on antigen concentration in vaccines is important. Because the potency of tested vaccine will be deduced from the potency of reference vaccine, dilutions used should give the effects that satisfy the linearity of Regression “Dose – Effect” at the interval confident of 95%. And the comparison of 2 linear regressions of 2 vaccines will make the results more accurately than when this condition is not satisfied.

– It is also necessary to choose an appropriate statistic method to analyze the experimental results from NIH test. Angular Transformation and Analysis of variance will be the tools to explore the significant differences of challenge doses used from experience to experience, to control the consistency from lot to lot and to detect the degradation of reference vaccine or an abnormal manipulation in performing the technique. It would help manufacturers to manage objectively the quality of rabies vaccine going to the market.