COVID-19 BREAKTHROUGH INFECTIONS AND DIAGNOSTIC PERFORMANCE OF RT-PCR AND RAPID ANTIGEN TESTS AMONG SYMPTOMATIC INDIVIDUALS: A PROSPECTIVE OBSERVATIONAL STUDY
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Keywords
COVID-19, breakthrough infection, vaccination, RT-PCR, rapid antigen test, SARS-CoV-2 variants
Abstract
Background: COVID-19 vaccination has significantly reduced global morbidity and mortality; however, breakthrough infections continue to occur, particularly with emerging SARS-CoV-2 variants possessing immune-escape characteristics. Accurate diagnostic evaluation of breakthrough infections is essential, especially comparisons between RT-PCR and rapid antigen tests (RATs).
Objectives:
(1) To determine the incidence of breakthrough infections among vaccinated individuals.
(2) To evaluate the diagnostic efficacy of RT-PCR and RATs in symptomatic COVID-19 patients.
(3) To compare clinical severity and haematological profiles in vaccinated versus unvaccinated infected individuals.
(4) To analyse the role of SARS-CoV-2 variants in breakthrough infections.
Methods: A prospective study was conducted (Nov 2021–Dec 2024) at Index Medical College, Indore. All symptomatic suspected COVID-19 patients and vaccinated RT-PCR–positive individuals meeting CDC's breakthrough criteria were included. Nasopharyngeal swabs, sputum and BAL specimens were collected. RT-PCR and RAT performance, clinical severity, and haematological markers were evaluated.
Results: Breakthrough infections accounted for a considerable proportion of positive cases, particularly during Delta and Omicron waves. Vaccination significantly reduced disease severity, hospitalization and inflammatory marker levels. RT-PCR demonstrated superior sensitivity, detecting low-viral-load infections that RATs frequently missed. RAT showed reduced sensitivity in vaccinated breakthrough cases.
Conclusion: Breakthrough infections remain an important epidemiological phenomenon but are predominantly mild among vaccinated individuals. RT-PCR remains the diagnostic gold standard, while RATs serve as adjunct tools with limited sensitivity. Vaccination continues to offer strong protection against severe outcomes.
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Mr. Tajvar
Research Scholar, Department of Microbiology, Index Medical College, Indore, Madhya Pradesh, India. (Malwanchal University).
Dr. Ramanath K
Professor Department of Microbiology, Index Medical College, Indore, Madhya Pradesh, India. (Malwanchal University).