Vaccines provide one of the most effective health interventions, with a profound impact on reducing morbidity and mortality. When considering just 4 vaccines, WHO estimates that worldwide, 2.5 million deaths from diphtheria, tetanus, pertussis and measles are averted each year.1 Most vaccines administered routinely in populations are scheduled for infants and young children. In many countries with well-established immunisation programs, the incidence of vaccine-preventable diseases has sharply fallen and public attention has shifted towards issues of vaccine safety. Furthermore, over the next decade, several new vaccines will reach the market and be considered for national immunisation programs.
In collaboration with several institutions, the Swiss Tropical Institute participates in global reviews on the postmarketing evidence for safety and effectiveness of vaccines in targeted subpopulations. The aim is to contribute knowledge towards best immunisation policy and practice.
Phase I-III clinical trials capture and report more common vaccine-related adverse events. Pre-licensing studies, however, are not powered to detect rare adverse events, nor can they adequately represent certain subpopulations for whom vaccination may pose a higher benefit or risk. Continuous postmarketing, population-based surveillance thus plays a crucial role in identifying any rare, serious vaccine-related adverse events and unexpected effects in vaccinated subgroups.
In general, there is a higher expectation for safety of primary prevention measures such as vaccination, because they target healthy recipients. The vaccine is expected to provide substantial health benefits that are proven and safe; any serious risks from the intervention are expected to be known and rare. Other important areas of immunisation safety include vaccine quality, safe technique for administration, and safe disposal of vaccine-related products.
Most of our current understanding of vaccine-related adverse events remains largely from data from industrialised countries. In 2004, only 68% of countries identified a national system to report vaccine-related adverse events.1 There is a need to improve global postmarketing surveillance of vaccine safety, and to consider safety monitoring a fundamental component of all immunisation programs.
Reference
1. WHO (2005). Global status of immunization safety: report based on the WHO/UNICEF Joint Reporting Form, 2004 update. Weekly epidemiological record 80: 361-8.
Resources
WHO Immunization Safety
http://www.who.int/immunization_safety/en
Tippi Mak
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