Standardizing case definitions for monitoring the safety of maternal vaccines globally: GAIA definitions, a review of progress to date

The Global Alignment on Immunization Safety Assessment in Pregnancy (GAIA) consortium was established in 2014 to develop a unified approach for monitoring vaccine safety during pregnancy. This review identified and described studies evaluating the performance of the 26 standardized adverse event definitions developed by GAIA. A literature search was conducted, and four studies assessing 13 GAIA case definitions were identified. Notably, only high-income settings were included in these assessments. The investigators provided recommendations to enhance the definitions, such as ensuring consistency, minimizing ambiguity, and allowing higher-level criteria at lower confidence levels. Future research should focus on evaluating the remaining case definitions, especially in low- and middle-income settings.