Signal monitoring for adverse events following immunisation with
COVID-19 vaccines during the SARS-CoV-2-pandemic: an evaluation of the
South African surveillance system
Abstract
Purpose: Monitoring of adverse events following immunisation (AEFI) is
recommended for post-licensure surveillance. We investigated whether the
South African surveillance system could detect signals of
disproportionate reporting and whether these signals aligned with
globally identified AEFI and adverse events of special interest (AESI)
post-COVID-19 vaccination. Methods: This retrospective pharmacovigilance
study undertook disproportionality analysis of the National Department
of Health AEFI database from the start of the COVID-19 vaccine rollout
on 17/05/2021 to 31/12/2022. We complemented this with AEFI reports for
vaccines not on the routine Expanded Programme on Immunisation schedule,
to address potential masking of signals due to the high reporting rate
of COVID-19 vaccine AEFI. Results: During the study period, 3846 AEFI
were reported for 37,537,009 doses of COVID-19 vaccines (BNT162b2 and
Ad26.COV2.S) administered. The overall reporting rate was 10.2 per
100,000 doses, 18.1/100,000 and 7.9/100,000 for BNT162b2 and
Ad26.COV2.S, respectively. Comparison with other countries suggests
underreporting. Disproportionate reporting signals were obtained for
three and seven AEFI following BNT162b2 and Ad26.COV2.S vaccines,
respectively. An additional AEFI signal from Ad26.COV2.S emerged in the
augmented dataset, indicating masking. All Ad26.COV2.S signals, and one
BNT162b2 signal, appear in the vaccines’ product information. Among nine
AESI evaluated, myocarditis/pericarditis presented as a signal of
disproportionate reporting following BNT162b2 vaccination. Conclusion:
This study is one of the first from a lower middle income country, using
a spontaneous reporting system for signal detection post-COVID-19
vaccination. Signals aligned with those reported globally. The study
highlights needs to further investigate underreporting, masking, and
system attributes for system strengthening.