The Global Vaccine Safety Initiative: enhancing vaccine pharmacovigilance capacity at country level

Large-scale immunization programmes now extend to all parts of the world, including least developed countries, where they reach unprecedented numbers of people. The number of vaccine doses administered worldwide continues to increase as new vaccines are developed and made available, and more people have access to immunization services. Development of immunization programmes in lowand middle-income countries (LMICs) has increased immunization coverage, which in turn has led to a reduction in vaccine-preventable diseases. However, as vaccine use has increased in LMICs, so has public attention to vaccine safety issues, as happened previously in high-income countries. This has created additional vulnerability for all immunization programmes. Whether or not they are well founded, concerns about serious adverse events following immunization may rapidly undermine public confidence and become a serious threat to effective vaccination strategies, eroding the enormous gains in disease control achieved with decades of effort. Patterns of global access to vaccines and programme implementation are evolving. In the past, vaccines that became available for programmes in LMICs had already been used for years in high-income countries. Currently, however, some newly developed vaccines (e.g. rotavirus vaccine) have become available in LMICs only a short time after being introduced in high-income countries. Other new vaccines, such as meningococcal A vaccine or candidate vaccines against dengue and malaria, may be introduced first in LMICs, where the capacity for adequate safety monitoring is limited. Some of these vaccines may contain elements that have not been widely used in humans, including multiple antigens or recombinant viral vectors. As a result, for the first time people in LMICs are being administered with newly developed vaccines in settings where monitoring capacity is limited. In addition, there are important population groups for which the safety profile of vaccines may differ; for example, people with immune deficiency (in areas with high rates of human immunodeficiency virus prevalence), malnutrition and chronic conditions, as well as pregnant women. Although toxicity and safety are monitored in pre-licensing studies, the number of vaccine recipients observed in such studies is limited. Also, because serious vaccine reactions are very rare, it is generally only after licensure and administration to millions of people that such reactions are detected. Thus, a well-designed and well-structured global approach that involves adequate monitoring of large populations is required for early recognition of potential issues, timely investigation of concerns, informed decision-making and corrective actions.