ORIGINAL RESEARCH article
Front. Med.
Sec. Infectious Diseases: Pathogenesis and Therapy
Volume 12 - 2025 | doi: 10.3389/fmed.2025.1592019
False positive results in the Widal test in adults immunized with the Commirnaty (Pfizer-BioNtech) and BBIBP-CorV (Sinopharm) vaccines against COVID-19
Provisionally accepted
Jeel Moya-Salazar1*
Lizbeth Y Ciprian2Víctor Rojas-Zumaran3Belén Moya-Salazar4
Eliane A. Goicochea-Palomino5
Hans Contreras-Pulache4- 1Facultad de Ciencias de la Salud, Universidad Privada del Norte, Lima, Peru
- 2Clínica Celestial de Ayacucho, Lima, Peru
- 3Hospital Nacional Docente Madre Niño San Barotlomé, Lima, Peru
- 4Norbert Wiener Private University, Lima, Lima, Peru
- 5Technological University of Peru, Lima, Peru
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Introduction: Vaccination against COVID-19 has generated a dramatic reduction in deaths and infections worldwide. However, there may be cross-reactivity with numerous biochemical and immunological markers. The Widal test for the detection of typhoid fever is an antigen-antibody test that can be affected by vaccination, causing errors in the results, so we determined the frequency of false positive results of the Widal test in adults vaccinated with Commirnaty (Pfizer -BioNtech) and BBIBP-CorV (Sinopharm) vaccines.We conducted a cross-sectional study analyzing the titers of the serum agglutinins (S. Typhi O and H antigen, and S. Paratyphi A and B antigen) in 50 adults.The proportion of false positives for O, H, A, and B antigens was 60%, 44%, 8%, and 40%, respectively (total false positives = 38%). The Wildal tests' results of patients with Commirnaty vaccine had higher false-positive dilution titers for O antigen [titer 1/400 (7.1%) and 1/800 (9.5%)] and H antigen [titer 1/400 (4.8%) and 1/800 (17.6%)]. We found differences in the paratyphic B by age and gender (p<0.05). Conclusion: Our results suggest misleading results of the Widal test in patients vaccinated against COVID-19, mainly in those vaccinated with Commirnaty. It is important to monitor and evaluate the results of routine immunological tests to ensure the quality of medical care.
Keywords: COVID-19, False positive, Vaccine, Salmonella, Widal test, SARS-CoV-2, in vitro, Peru
Received: 14 Mar 2025; Accepted: 29 Jul 2025.
Copyright: © 2025 Moya-Salazar, Ciprian, Rojas-Zumaran, Moya-Salazar, Goicochea-Palomino and Contreras-Pulache. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Jeel Moya-Salazar, Facultad de Ciencias de la Salud, Universidad Privada del Norte, Lima, Peru
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