Article Text

Download PDFPDF
Antibody response and self-reported adverse reactions following vaccination with Comirnaty: a pilot study from a Croatian university hospital
  1. Ivana Lapić,
  2. Dunja Rogić,
  3. Dragana Šegulja,
  4. Ljiljana Zaninović
  1. Department of Laboratory Diagnostics, University Hospital Centre Zagreb, Zagreb, Croatia
  1. Correspondence to Mrs Ivana Lapić, Department of Laboratory Diagnostics, University Hospital Centre Zagreb, Zagreb 10000, Croatia; ivana.lapic{at}


This study aimed to determine antibody responses against SARS-CoV-2 spike (S) after both BioNTech–Pfizer Comirnaty vaccine doses and study the correlation with self-perceived adverse reactions. Antibodies determination with Elecsys anti-SARS-CoV-2 S assay was performed a day prior to or just before administration of the second dose and 8–13 days after the second dose. Participants selected from a predefined list of the experienced local (injection site reactions) and/or systemic (fatigue, headache, myalgia, arthralgia, chills and fever) post-vaccination adverse reactions. An average 100-fold increase in antibody titre in naive vaccinees was observed between the two time points (median 67 U/mL vs 2841 U/mL, p<0.001). Participants aged below 50 had higher antibody titres (median 99 U/mL vs 26 U/mL, p=0.003 after the first dose; median 3617 U/mL vs 2556 U/mL, p=0.026 after the second dose). All reported adverse reactions were mild-to-moderate, with more participants declaring systemic reactions after the second dose (p=0.001), without a clear correlation with antibody titre.

  • COVID-19
  • antibodies
  • immunoglobulins
  • vaccines

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Handling editor Tahir S Pillay.

  • Contributors IL and DR designed the study, analysed and interpreted the data and wrote the manuscript. DŠ and LZ performed laboratory analyses and acquisition of data. All authors drafted the article and approved its final version for submission.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.