Using Population-Based Structures to Actively Monitor AEFIs during a Mass Immunization Campaign - A Case of Measles-Rubella and Polio Vaccines

"To sustain public confidence, compliance, and acceptance of immunization programs, it is important to have active safety surveillance to find AEFIs [adverse events following immunisation] during mass immunization campaigns and to report these events openly and transparently."

One strategy national immunisation programmes use to increase uptake of vaccines is mass immunisation. Such campaigns result in large numbers of vaccine exposures, which means that more adverse events following immunisation (AEFIs) occur, irrespective of their severity. Whether caused by a vaccine or coincidental, AEFIs may cause unnecessary and unjustified suspicion towards vaccines. Low- and middle-income countries (LMICs) such as Uganda depend on passive surveillance systems to monitor vaccine safety, but these systems often suffer from low reporting. This study explores the role of active vaccine surveillance in Iganga district, Uganda.

In October 2019, Uganda carried out a national mass campaign to vaccine all children under 15 years of age against measles, rubella, and polio using the measles and rubella (MR) bivalent and oral polio (bOPV 1&3) vaccines. The vaccination campaign engaged schools, vaccination posts, village health team (VHT) members, and local councils (LC1), in addition to local government structures at the parish, subcounty, health subdistrict, and district levels. An active surveillance system followed up with children either in the communities or at school for 14 days during the MR & bOPV campaign in Iganga district. This was a complementary system alongside the passive reporting system adopted by the National Drug Authority (NDA) of Uganda.

Specifically, immunised children were followed up with by teachers at school and community mobilisers (VHTs) in communities. The teachers and VHTs were given basic training on vaccine safety monitoring and vigilance, research ethics, and reporting. Parents of children and schoolgoing children were provided with leaflets in both English and Lusoga (local language) that had information on vaccination and possible AEFIs.

The teachers monitored children immediately after immunisation and in the following days while at school. The trained VHTs either visited households or contacted the caretakers on day 1, 2-3 days, 10 days, and 14 days after immunisation. Teachers directly asked schoolgoing children, while VHTs asked the caretakers, if there was any AEFI and if they suspected the event could have been as a result of the vaccine received during the mass vaccination campaign. A research supervisor worked with the teams to observe and manage any AEFI or refer children to the nearest health facility for further management when it was considered serious. The telephone contact details of the supervisors were made available to all participants.

Data were collected using a paper-based case report tool developed in collaboration the National Pharmacovigilance Centre (NPC) to capture AEFIs. All reports collected through this active follow-up were shared with the National Pharmacovigilance Centre (NPC) of the NDA and the Uganda Expanded Program on Immunization (UNEPI) at the Ministry of Health for further analysis or assessment and were added to the national line listing.

Out of 9,798 children followed up on, 382 (3.9%) reported at least one AEFI; in total, 517 AEFIs were reported. High temperature was the most reported event for both the mono dose (MR) and the combination (MR & bOPV). All 382 children cleared the AEFIs within 2 days, with 343 (90%) children reporting mild or moderate AEFIs and only 39 (10%) reporting severe AEFIs. The reported AEFIs are known and are mentioned in the vaccine leaflets with similar severity classification. Generally, more cases were reported from schools than from the communities: "The surveillance established at school was more likely to easily identify children who missed school on day one than VHTs. Schools can play an important role in ensuring vaccination activities are a success..., including by reporting AEFIs."

The rate of AEFIs in the present study was higher than the rate reported by the UNEPI for the entire country, reflective of the difference between active vaccine safety monitoring and passive surveillance, which relies on self-reporting of AEFIs to health facilities and later to the Ministry of Health. This initiative reached more vaccine recipients, who were able to report more AEFIs in this campaign, compared to similar campaigns recommended by the World Health Organization (WHO) for LMICs.

In conclusion: "Surveillance efforts that leverage on the use of community structures such as VHTs and schoolteachers complement the traditional passive reporting system, especially during mass vaccination campaigns. This not only increases the number of reports but builds public confidence in health system programs and mitigates vaccine hesitancy in LMICs. The active AEFI monitoring system provided extra information to national vaccine regulatory bodies. Countries need to conduct regular active reporting in order to obtain an accurate picture on overall AEFIs and to monitor trends and changes."