Determining the reliability of rapid SARS-CoV-2 antigen detection in fully vaccinated individuals

J Clin Virol. 2022 Mar;148:105119. doi: 10.1016/j.jcv.2022.105119. Epub 2022 Feb 19.


Background: Rapid antigen detection tests (RADT) are commonly used as SARS-CoV-2 diagnostic tests both by medical professionals and laypeople. However, the performance of RADT in vaccinated individuals has not been fully investigated.

Objectives: RT-qPCR and rapid antigen detection testing were performed to evaluate the performance of the Standard Q COVID-19 Ag Test in detecting SARS-CoV-2 breakthrough infections in vaccinated individuals.

Study design: Two swab specimens, one for RT-qPCR and one for RADT, were collected from vaccinated individuals in an outpatient clinic. For comparison of RADT performance in vaccinated and unvaccinated individuals, a dataset already published by this group was used as reference.

Results: During the delta wave, a total of 696 samples were tested with both RT-qPCR and RADT that included 692 (99.4%) samples from vaccinated individuals. Of these, 76 (11.0%) samples were detected SARS-CoV-2 positive by RT-qPCR and 45 (6.5%) samples by the Standard Q COVID-19 Ag test. Stratified by Ct values, sensitivity of the RADT was 100.0%, 94.4% and 81.1% for Ct ≤ 20 (n=18), Ct ≤ 25 (n=36) and Ct ≤ 30 (n=53), respectively. Samples with Ct values ≥ 30 (n=23) were not detected. Overall RADT specificity was 99.7% and symptom status did not affect RADT performance. Notably, RADT detected 4 out of 4 samples of probable Omicron variant infection based on single nucleotide polymorphism analysis.

Conclusion: Our results show that RADT testing remains a valuable tool in detecting breakthrough infections with high viral RNA loads.

Keywords: Antigen test; Delta; Omicron; RT-qPCR; SARS-CoV-2; Vaccination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Viral / analysis*
  • COVID-19 Serological Testing / standards*
  • COVID-19* / diagnosis
  • Humans
  • Reproducibility of Results
  • SARS-CoV-2
  • Sensitivity and Specificity
  • Vaccination*


  • Antigens, Viral

Supplementary concepts

  • SARS-CoV-2 variants