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    Poster Networking

    Diagnostics and OMICs

    Poster Networking Session

    PB1191 - Prevalence of Anti-PF4 Antibodies in a Healthy Brazilian Population After Immunization with AstraZeneca vaccine

    Tuesday, June 27, 2023
    18:30 – 19:30 ET
    Room: Exhibition
    Background: All the reported VITT (Vaccine-Induced Immune Thrombotic Thrombocytopenia) cases had positive anti-PF4 antibodies ELISA results. However, few studies have been performed to assess the presence of these antibodies in healthy donors who were immunized by adenoviral vector-based vaccinations for COVID-19.

    Aims: This project aimed to assess the prevalence of anti-PF4 antibodies in 22 healthy Brazilian donors 10 days before and 10 days after the second shot of the ChAdOx1 nCoV-19 vaccine (AstraZeneca).

    Methods: Samples were selected from donors who took the ChAdOx1 nCoV-19 vaccine (AstraZeneca). Hemogram tests were performed, as well as 3 different anti-PF4 antibodies immunoassays – ELISA, LIA and CLIA – 10 days before and 10 days after the second shot. All the results went through statistical analysis.

    Results: All anti-PF4 antibodies measurements were negative ( < 1) in all methodologies, before and after the 2nd dose. Nevertheless, the ELISA test detected lower concentrations than the other tests, and the LIA test had more discrepant results than the others. The platelet count presented a slight decrease after the second dose, but with no apparent clinical effect on the individuals’ clinical status.

    Conclusion(s): Healthy individuals after AstraZeneca vaccination, it was concluded, have a small prevalence of anti-PF4 antibodies. The results, although negative, show us that exposure to the vaccine can cause the presentation of these antibodies even in individuals who don’t develop VITT. This conclusion correlates with what is observed in HIT. However, exposure to heparin appears to cause a higher concentration of anti-PF4 antibodies in healthy individuals than vaccination with AstraZeneca.
    The decrease in platelet count had no clinical relevance, but it was noted that when platelets decrease, the antibody concentration increases. Also, ELISA test results were more accurate in measuring anti-PF4 antibodies, especially when compared to the LIA results. This is similar to VITT-positive patients, where ELISA is the most reliable immunoassay.