Most COVID-19 vaccine adverse events detected within 48 hours in Ethiopia: implications for cohort event monitoring efficiency in resource-limited settings.

Authors

Tigist Dires Gebreyesus, Teshita Shute, Asnakech Alemu, Alemseged Beyene Berha, Mehiret Maru, Habtamu Gashaw, Meron Kifle, Julie Doherty, Albert Figueras

Published in

European journal of clinical pharmacology. Volume 82. Issue 8. Jul 24, 2026. Epub Jul 24, 2026.

Abstract

The World Health Organization recommends cohort event monitoring with a 30-day follow-up period for vaccine safety surveillance in low- and middle-income countries (LMICs). However, in resource-limited settings, operational and logistical constraints necessitate evaluation of the efficiency and feasibility of this follow-up duration.
We conducted an analysis of a prospective active surveillance study of 10,948 adults who received the Pfizer COVID-19 vaccine in Ethiopia (August 2021-June 2022), using immediate observation and telephone follow-up on days 2, 4, 7, 14, 21, and 30.
Among 10,948 participants, 4,236 (38.7%; 95% CI: 37.8-39.6%) reported at least one adverse event following immunisation (AEFI), with 6,174 total events recorded. Of all events, 88.2% were detected within 48 h (1.8% immediate, 86.4% at day 2), while 11.8% were identified during subsequent follow-up between days 4 and 30. Seven reactogenic symptoms comprised 93.8% of AEFIs. No serious AEFIs or adverse events of special interest were identified. Over nine months, 138 healthcare professionals captured predominantly mild, expected reactions through extended surveillance.
Most COVID-19 vaccine adverse events in Ethiopia occurred within 48 h of vaccination, empirically suggesting that extended full-cohort CEM could yield diminishing informational returns in low- and middle-income country settings. A hybrid surveillance approach combining intensive short-term active surveillance during the first 48 h, enhanced passive reporting, and sentinel hospital networks with adequate diagnostic capacity could offer a more sustainable and operationally realistic framework. These findings are offered as an evidence-based reference for national regulatory authorities planning or conducting emergency vaccine safety surveillance in comparable contexts, supporting a transition from product-centred extended monitoring towards patient-centred, resource-adapted pharmacovigilance.
Not applicable.

PMID:
42493669
Bibliographic data and abstract were imported from PubMed on 24 Jul 2026.

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