Most vaccine-associated adverse events were mild and expected and support a favorable benefit-risk profile and highlight the importance of continuous pharmacovigilance systems for vaccine safety monitoring.
Abstract
Objectives
To describe the distribution and characteristics of adverse events following immunization (AEFI) using a large US pharmacovigilance database.
Methods
A retrospective descriptive analysis of Individual Case Safety Reports (ICSRs) from the FDA AEMS database (January 2017-March 2026) was conducted. Reports were analyzed by vaccine type, adverse event terms, demographics, reporting year, and reporter category.
Results
A total of 2 169 603 ICSRs were identified, with 44.0% classified as serious. COVID-19 vaccines accounted for 78.4% of reports, reflecting mass vaccination campaigns. The most frequently reported events were headache (12.8%), pyrexia (11.8%), and fatigue (11.1%), predominantly non-serious and consistent with known reactogenicity profiles. Reporting peaked in 2021 (48.8%). Females accounted for 60.6% of reports. Non-COVID vaccines contributed substantially fewer reports.
Conclusions
Most vaccine-associated adverse events were mild and expected. Findings support a favorable benefit-risk profile and highlight the importance of continuous pharmacovigilance systems for vaccine safety monitoring.
ABSTRACT Vaccination is a principal method of infectious disease prevention, but its association with rheumatoid arthritis (RA) remains controversial. This study assessed vaccine‑associated RA using the Vaccine Adverse Event Reporting System (VAERS). Data from 1990 to 2026 were extracted. Descriptive statistics, Weibull fitting, and disproportionality analysis using four methods, including the reporting odds ratio (ROR), along with subgroup analyses by age, sex, and pre‑/post‑COVID, were performed. Among 11,532,185 reports, 34,498 RA‑related adverse events (AEs) (0.03%) involved 5006 subjects. Females comprised 77.9% and 18–65 predominated. Serious outcomes occurred in 13.48%. Most AEs (47.49%) were musculoskeletal. 47.0% occurred within 7d (median 5.4), indicating early failure. The COVID‑19 vaccine had the most reports (n = 24,266) but a weak signal (ROR = 1.25); the Lyme disease vaccine (ROR = 27.81), the rubella vaccine (ROR = 5.69), and the anthrax vaccine (ROR = 3.90) exhibited the strongest signals. Subgroup signals: Lyme disease vaccine except 2021–2026; rubella vaccine only in females/≤17; anthrax vaccine in 18–64. RA‑related vaccine AEs are extremely rare, mainly musculoskeletal and within 1 week. High COVID‑19 volume did not align with its weak signal, while strong signals for the Lyme disease, rubella, and anthrax vaccines reflected specific populations. No strong disproportionality signal was found. However, VAERS is passive, cannot establish causality or confirm safety.
Pan Lu, Mengqi Lou, Z.-C. Qiu et al.· Human Vaccines & Immunothera...· 0 citations
ObjectiveThis study aimed to identify characteristics of adverse events following immunization (AEFI) reporting systems and vaccine adverse events reporting systems (VAERS) including technical platforms, user groups, data elements, functional and non-functional requirements.MethodsIn this scoping review, various databases were searched from 1st January 2015 to 31st December 2024, and all types of studies that explained AEFI reporting system/VAERS characteristics were considered. The findings were reported descriptively.ResultsDifferent technical platforms including web-based, mobile-based, or hybrid platforms were used by multiple user groups. Data elements included personal, clinical, vaccination, and adverse events data. The functional requirements included recording vaccination and adverse events data as well as generating reports. Non-functional requirements were related to system security, data privacy, etc.ConclusionThis review presented a set of characteristics that has been considered for different AEFI reporting systems and VAERS. The results can be used for designing more comprehensive AEFI reporting systems in different countries. These features along with new digital technologies and analytical tools including artificial intelligence offer more potential to enhance efficiency and effectiveness. Future research should focus on AI-driven methodologies, including natural language processing, machine learning techniques, and predictive analytics, while addressing ethical, regulatory, and practical challenges.
Hassan Asadi, H. Ayatollahi, S. Zahraei et al.· Health Informatics Journal· 0 citations
Background Herpes zoster causes substantial morbidity in older adults, and US herpes zoster vaccination shifted from the live-attenuated Zostavax to the recombinant Shingrix after 2017 We describe the post-marketing adverse-event profile of these vaccines reported to the US Vaccine Adverse Event Reporting System (VAERS) and identify events reported disproportionately for herpes zoster vaccines. Methods In a descriptive cross-sectional design, we analyzed 69,822 US VAERS reports listing a herpes zoster vaccine, received 1 January 2017–25 April 2024. Reports were characterized by demographics, brand, MedDRA preferred terms and system organ classes, and US FDA serious-event indicators; brand subgroups were summarized descriptively. Reporting odds ratios (RORs) with 95% confidence intervals compared the combined herpes zoster vaccine cohort with all other US VAERS reports. Reporting followed the STROBE guideline. Results Shingrix accounted for 58,813 (84.2%) reports and Zostavax for 10,507 (15.0%). Reports were predominantly in women (63.9%) and adults aged 50–69 years (median age 64.0 years). Reactogenic and injection-site terms predominated—pyrexia (18.3%), pain (17.8%), chills (15.9%), headache (15.4%), and injection-site pain (14.2%). Against all other US reports, injection-site and influenza-like reactions were modestly enriched (e.g., injection-site pain ROR 2.92), whereas vesicular rash was strongly over-reported (ROR 43.70); the latter was concentrated in live-vaccine reports and reflects reported vaccine-strain disease rather than an unexpected adverse reaction. Serious reports comprised 6.6% of the cohort (2.9% Shingrix, 27.6% Zostavax). Conclusion Eight years of VAERS data are consistent with the recognized reactogenicity of the recombinant vaccine and the live-vaccine profile of Zostavax; most reported events were transient and non-serious. These hypothesis-generating disproportionality signals require confirmation in active surveillance with denominator data.
Mohammed Alkharaiji, Salahaden R. Sultan, Yousif A. Kariri et al.· Frontiers in Medicine· 0 citations
Background : Vaccination remains a vital global public health intervention, yet maintaining public trust requires rigorous monitoring of Adverse Events Following Immunization (AEFIs). While passive safety surveillance often suffers from under-reporting, systematic prospective monitoring provides accurate, active capture of both solicited (anticipated reactogenicity) and unsolicited (unexpected occurrences) events. Differentiating true vaccine reactions from coincidental childhood illnesses in developing immune systems requires standard causality frameworks like the WHO-UMC and Naranjo scales. This study evaluates the frequency, nature, and severity of these adverse events across distinct paediatric age cohorts to establish a precise, evidence-based safety profileObjective: To identify, monitor, and assess both solicited and unsolicited adverse events following immunization in children under twelve.
Methods: In this one-year, prospective observational study, 760 children under twelve who experienced vaccination-related problems at a tertiary teaching hospital were enrolled and divided into three age groups. Data on demographics, vaccine details, adverse events, severity, and causality were collected and analyzed using Naranjo’s scale and WHO-UMC criteria. Statistical significance was set at p<0.05.
Results: 210 solicited adverse events were documented in 174 patients; unsolicited adverse events occurred at varying rates across age groups. Group 3 (>5 years) had more severe adverse events (31.57%) compared to Groups 1 and 2 (p=0.003). Local adverse effects were more common in infants and toddlers (p=0.001). Most adverse events were mild and self-resolving.
Conclusion: Most adverse reactions following vaccination in children under twelve are mild and transient, with age-specific patterns observed.
Yisheng Jun’an® rabies vaccine exhibits a favorable safety profile with mild-to-moderate reactions, support its use in post-exposure prophylaxis, supporting its use in post-exposure prophylaxis.
Zhijie Cui, Lianfu Wang, Zhiyuan Ran et al.· Frontiers in Public Health· 0 citations
Acyclovir is the first-line treatment for neonatal herpes simplex virus infection; however, safety evidence in neonates remains limited. This study aimed to evaluate the safety profile of acyclovir in neonates using real-world pharmacovigilance data from the Food and Drug Administration Adverse Event Reporting System. This retrospective observational study analyzed adverse event (AE) reports in neonates (≤28 days) in which acyclovir was identified as the primary suspected drug in the Food and Drug Administration Adverse Event Reporting System from 2004 to Q3 2024. Disproportionality analyses were performed using the reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network, and empirical Bayesian geometric mean (EBGM). Positive risk signals were defined as those meeting the statistical significance criteria across all 4 methods. A total of 130 reports comprising 409 AEs were identified. Four system organ classes showed positive risk signals: skin and subcutaneous tissue disorders (ROR = 6.22, PRR = 5.88, lower limit of 95% confidence interval [CI] of the information component [IC025] = 1.98, lower limit of 95% CI of EBGM [EBGM05] = 4.16), general disorders and administration site conditions (ROR = 4.27, PRR = 3.47, IC025 = 1.47, EBGM05 = 2.85), hepatobiliary disorders (ROR = 3.85, PRR = 3.74, IC025 = 1.19, EBGM05 = 2.43), and renal and urinary disorders (ROR = 3.84, PRR = 3.70, IC025 = 1.24, EBGM05 = 2.51). At the preferred term level, 12 positive signals were detected, with the strongest signals observed for infusion site necrosis/edema (ROR = 939.92, 95% CI: 97.56–9055.25), arthritis (ROR = 179.47, 95% CI: 52.33–615.44), skin exfoliation/necrosis (ROR = 131.18, 95% CI: 46.00–374.06), and Kawasaki disease (ROR = 114.20, 95% CI: 36.21–360.15). Notably, Kawasaki disease, rectal hemorrhage, and necrotizing colitis were not described in existing product labeling. Acyclovir use in neonates may be associated with immune, gastrointestinal, hepatic, and renal AEs, underscoring the need for careful clinical monitoring. Further prospective studies are warranted to validate these associations.
Long-Bing He, Bo Wang, Yang Wang et al.· Medicine· 0 citations
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