For over 40 years, efforts to control the spread of measles through large scale vaccination programs have been highly effective. Some research suggests that national immunization programs now prevent 80+ million cases of measles and save 4.5 million lives annually. Despite high vaccination rates however, periodic outbreaks continue to occur and measles remains a key contributor to childhood mortality.
New research suggests that lapses in the “cold chain” may cause some Nigerian healthcare providers to unknowingly distribute measles vaccines with low potency. As a result, some vaccine recipients are not developing adequate protective antibodies which may make them vulnerable to measles infection.
A family in Ondo state, Nigeria.
Researchers at the University of Ilorin in Nigeria examined several batches of lyophilized Ruvax vaccines provided by UNICEF. The vaccines were stored in a freezer and then reconstituted using the manufacturer’s instructions. A total of 400 infants were enrolled in the study and vaccinated over 12 months; 286 (71.5%) returned to provide post-vaccination samples. Of this group, 68.8% developed protective antibody titers and the remaining 31.4% had low antibody titers that may not provide adequate measles protection.
The potency of the vaccine administered may be to blame. Researchers found that three of the six vials of measles vaccines tested had titers below the WHO minimum standard of 1,000 CCID50 per human dose. The low potency of vaccines has been confirmed in other studies carried out by Nigerian researchers. Immune response has been shown to be directly related to the titer of vaccine used.
The authors of the new study attribute the low potency to several factors including inadequate vaccine storage and handling. The authors note that the immunization clinic suffers from regular power interruptions, has no backup power, and, as a result, vaccines stored may experience repeated thawing and freezing. The lack of thermometers adds to the challenge of verifying lapses in the cold chain that may indicate vaccine spoilage.
The cold chain system contains many “links,” and all are subject to the potential for human error and equipment malfunction. Vaccine efficacy is the shared responsibility of all who handle the product from the time it is manufactured to the time it is administered. When breakdowns occur, the consequences can be costly and potentially harmful.
As an alternative to reliance on the cold chain, we believe that VBI’s thermostable technology platform will enable the development of vaccines and biologics that can withstand storage or shipment at constantly fluctuating or elevated temperatures. Once commercialized, this technology could increase vaccine safety, efficacy, and access in emerging markets like Nigeria. To learn more about our thermostable technology, contact us.