Stability of lyophilized measles vaccine: Stabilizers and Temperature parameters: Heat-Stability of lyophilized measles vaccine

The effectiveness of live measles vaccine is based on numerous factors like complete attenuation of the vaccine virus, appropriate stabilizer, pH, exposure to light, and also on the maintenance of cold chain (temperature) till the time vaccine is injected to the end-users which are normally infants in case of Measles. The purpose of the present study was the estimation of the thermal stability of the vaccine using three different types of stabilizers for lyophilization. All batches were prepared using different types (ST, SH & SG) of stabilizer and tested in triplicate against reference according to WHO’s method of Spearman-Karber for calculation of vaccine titer. Potency and accelerated stability were carried out by incubating each of the three vaccines at 2-4oC and 37oC for seven days. For calculation of potency drop at increasing temperatures, titer was calculated for consecutive fourteen days at 24 hours interval, three vials from each vaccine type were incubated at 4oC, 25oC, 37oC, and 41oC. The potency observed was between log 103.64 to 104.89. Thus, making them fall within the WHO laid down criteria. These potency results also demonstrated that ST based stabilizer was comparatively more stable among the three. It also verified that vaccine remains stable for 14 days at 37oC but rapidly loses potency at 41oC even after 4 days. This study verifies that regardless of external hard weather conditions (e.g., Pakistan), maintenance of manufacturer recommended storage temperature and effective use of proper stabilizer is the only way to ensure the stability of the measles vaccine.