Published in PLOS One on 2026-07-10, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: Kizito Kayumba, Alemayehu Duga, Mosoka Papa Fallah, Claire Tshidibi, Nicky Lubaki, Barnabas Coulibaly, Benjamin Djoudalbaye, Efire Nora Sylvana, Senga Lucy Sembuche, Tedi Tilahun, Murtala Jibril, Carlos Kilowe, Aminu Kuba, Antoine Mafwila Lusala, Nebiyu Dereje, Nicaise Ndembi, Tajudeen Raji, Ngashi Ngongo
Source: PLOS One • DOI 10.1371/journal.pone.0309628
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Post-marketing safety surveillance is essential for ensuring vaccine safety and maintaining public trust, particularly in African settings where evidence on the safety of COVID–19 vaccines remains limited. This study aimed to determine the overall incidence and types of AEFIs, as well as the factors associated with their occurrence, during COVI-19 mass vaccination campaigns in Democratic Republic of Congo.
From December 1–29, 2023, a prospective safety surveillance study was conducted in Kinshasa Province. Participants were surveyed through phone calls from day 1–28 following COVID-19 vaccine administration. AEFI incidence rates were calculated by type of vaccine, sex, number of dose and age group. Factors associated with AEFIs were identified using multivariable logistic regression models, expressed by adjusted odds ratio and its 95% confidence interval.
The study included 4766 participants. Their median [IQR] age was 36 [27−48] years and 2503 (53%) were males, 94.63% received the J&J vaccine while 256 (5.37%) received the BNT162b2 vaccine. Incidence of AEFIs was 23.75% (95%CI: 22.54%−24.99%). AEFIs mostly reported were fever (9.61%, 95%CI: 8.88%−10.48%), injection site pain (9.00%, 95%CI: 8.20%−9.85%), headache (4.11%, 95%CI: 3.57%−4.72%), stiffness (1.51%, 95%CI: 1.18%−1.89%) and myalgia (1.15%, 95%CI: 0.87%−1.49%). The incidence of AEFIs was higher for the BNT162b2 vaccine at 34.48% (95% CI: 28.57%−40.54%) vs. 23.15% (95% CI: 21.92%−24.41%) for the J&J vaccine. Compared to participants aged 18−59 years, those under 18 years old were associated with decreased odds of reporting any AEFI (aOR= 0.26, 95%CI: 0.13–0.88) and injection site pain (aOR=0.18, 95%CI: 0.05–0.75). Those aged 60 years and older were associated with decreased odds of reporting any AEFI (aOR= 0.78, 95%CI: 0.62–0.99) and fever (aOR=0. 63, 95%CI: 0.43–0.92).
Approximately one-quarter of participants reported AEFI. The observed association with vaccine type and age underscores the need for systematic vaccine safety monitoring in the population. This is critical for guiding future vaccination strategies tailored to individuals who may be more susceptible to AEFIs.
Introduction and setting
Vaccines approved for use in national immunization programmes (NIPs) are deemed safe and effective based on robust evidence from randomized controlled clinical trials (RCTs) [1]. However, despite the rigorous evaluation conducted during clinical development, rare adverse events (AEs) may go undetected due to the limited size and duration of these trials. Therefore, post-marketing safety surveillance is essential after the introduction of vaccines like those for COVID-19 into public immunization programs to identify rare and previously undocumented adverse events (AEs). For instance, the non-replicating vector COVID-19 vaccines such as those from AstraZeneca and Johnson & Johnson have been linked to rare cases of central venous sinus and thrombocytopenia, occurring at an estimated rate of approximately 4 cases per million vaccinations [2]. Similarly, messenger RNA (mRNA) vaccines, such as the Pfizer-BioNTech BNT162b2, have been associated with rare side effects including anaphylaxis and myocarditis [3].
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider public health desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Kizito Kayumba, Alemayehu Duga, Mosoka Papa Fallah, Claire Tshidibi, Nicky Lubaki, Barnabas Coulibaly, Benjamin Djoudalbaye, Efire Nora Sylvana, Senga Lucy Sembuche, Tedi Tilahun, Murtala Jibril, Carlos Kilowe, Aminu Kuba, Antoine Mafwila Lusala, Nebiyu Dereje, Nicaise Ndembi, Tajudeen Raji, Ngashi Ngongo. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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