Progress in Immunization Safety Monitoring — Worldwide, 2020–2022

Discussion

Compared with 2020, most WHO regions made progress toward achieving the two immunization safety monitoring measures in 2021 and 2022, by attaining the Global Advisory Committee for Vaccine Safety’s indicator of reporting at least one serious AEFI per 1 million total population per year, and by jointly reporting AEFI data from EPIs and NRAs. Progress has been particularly notable in AFR and EMR, where WHO has continued to support vaccine safety training and the development of standardized data collection tools and national AEFI surveillance system guidelines. Despite this progress, however, all WHO regions continue to report low percentages of countries jointly reporting EPI and NRA AEFI data; although EMR achieved the highest regional percentage of WHO countries jointly reporting EPI and NRA AEFI data, only 50% of countries in the EMR reported both. Fewer than one half, 92 (43%) of 215 WHO countries are currently meeting the target for the new safety monitoring indicator, and only in EUR are more than one half of countries reporting, demonstrating that additional work is needed to strengthen global vaccine safety monitoring.

The recent COVID-19 pandemic response and subsequent national immunization activities likely contributed substantially to the progress in global immunization safety monitoring, in large part because of increased funding and provision of intensified technical support from global partners. With nationally focused activities to increase COVID-19 vaccine distribution and vaccination coverage paired with innovative vaccine safety monitoring approaches (e.g., smartphone applications), the highest proportion of WHO countries meeting the new indicator was observed in 2021. Most AEFI cases reported in 2021 were associated with COVID-19 vaccines, reinforcing that case-based data from national AEFI surveillance systems can be shared globally (i.e., to VigiBase). Despite these gains, a slight decrease was observed in the proportion of WHO countries meeting the new reporting indicator in many WHO regions during 2022, likely because of a decline in national COVID-19 vaccination campaigns and less intensive AEFI surveillance. The current findings indicate that further measures are needed to strengthen global vaccine safety monitoring though technical support, standardized tools, and guidelines, and that better approaches to promote nationally coordinated AEFI reporting among EPIs and NRAs are needed.

Limitations

The findings in this report are subject to at least three limitations. First, this report relied only on data submitted to VigiBase to determine progress toward meeting the new AEFI surveillance indicator. Reporting to VigiBase is voluntary and varies by year. Some WHO countries might not consistently submit data to VigiBase and thus are not identified as meeting the AEFI surveillance indicator during the reporting period. Second, because of the distinct roles of reporting to VigiBase by NRAs and to the Joint Reporting Form by EPIs, assessment of the role the relationship among NRAs and EPIs plays in meeting the new immunization safety monitoring indicator was not possible. Finally, whereas other factors contribute to national capacity to develop and maintain an immunization safety system, this report focused on only two immunization safety measures: the new case-based indicator and the reporting source of AEFI data, which might not reflect the actual functionality of a national immunization safety surveillance system.

Implications for Public Health Practice

A shift to case-based reporting enables and promotes the use of AEFI data for action, including timely detection, reporting, investigation, and causality assessment by national AEFI committees, and response to reported serious AEFIs or clusters by national EPIs and NRAs. In addition, when shared globally, individual case safety reports can collectively contribute to the description of trends and regional characteristics of rare, but serious, AEFIs that might be difficult to detect through national aggregate data. Continued efforts in capacity building of immunization safety monitoring systems are needed to ensure and promote public confidence in national vaccination programs.