RESUMO
Background: The emergence of new variants of SARS-CoV-2 has led to the administration of different booster vaccines to mitigate COVID-19. Vaccines with adenoviral vectors have been rarely associated with vaccine-induced immune thrombotic thrombocytopenia (VITT). Objectives: This study aimed to describe 15 cases of VITT after the third and fourth doses of the COVID-19 vaccine in Brazil. Methods: Cases were reported after all kinds of anti-SARS-CoV-2 booster vaccinations between October 17, 2021, and September 4, 2022. Results: Of the 26 suspected cases, 15 cases of VITT were analyzed. Of these, 10 were classified as definite VITT, 2 as probable, 1 as possible, and 2 as unlikely. The estimated frequency of definite, probable, or possible VITT was 0.33 cases per million. Cases were assigned to ChAdOx1 (13 cases), Ad26.COV2.S (1 case), and BNT162b2 (1 case). None of the patients received an adenoviral vaccine as a primary vaccination. The average age of participants was 34 years, and symptoms usually appeared 8 days after vaccination. Headache was the most common symptom, and cerebral veins were the most affected thrombotic site. The overall mortality risk was 53%. Anti-platelet factor 4 enzyme-linked immunosorbent assay serology was positive in 11 out of 15 patients (73.3%), negative in 2 (13.3%), and missing in 2 (13.3%). Conclusion: The study confirms that VITT is linked to the first exposure to adenoviral vector vaccines. Since January 2023, Brazil has recommended preferably COVID-19 messenger RNA vaccines for individuals aged 18 to 39 years. We suggest that, in the current disease scenario, COVID-19 adenovirus vaccines should not be the first choice for individuals aged <50 years who have not received a previous dose of this type of vaccine.
RESUMO
OBJECTIVE: Describe a case series of vaccine-induced immune thrombotic thrombocytopenia (VITT) after COVID-19 vaccination in Brazil that included ChAdOx1 nCoV-19, Ad26.COV2.S and BNT162b2 vaccines, describing their clinical and laboratory characteristics. METHODOLOGY: Descriptive case series study using Bio-Manguinhos/Fiocruz/AstraZeneca Brazil and National Immunization Program/Ministry of Health (NIP/MoH) data on COVID-19 AEFI surveillance. We obtained patient-level data from pharmacovigilance for AEFI surveillance and used both the NIP/MoH and Bio-Manguinhos/Fiocruz pharmacovigilance databases to create the study database. Thirty-nine cases of suspect VITT were included, 36 after ChAdOx1 nCoV-19, one after BNT162b2 and two after Ad26.COV2.S vaccine. All cases were based on meeting the Brighton Collaboration criteria for VITT. The primary outcomes were clinical and laboratory features, site of thrombosis, and anti-PF4 ELISA, when available. RESULTS: Thirty-nine cases met the criteria, 38 of which were classified as level 1 and one as level 3 according to Brighton Collaboration. Most cases had the central nervous system (CNS) as the main site of thrombosis (21/39) and happened after the vaccine first dose (34/39). The median age of the cases was 41 years old (23 to 86 yo). Most of the cases (61.5%) occurred in women. The median interval between vaccination and onset of symptoms was 8 days (0-37 days). The platelet count and D-dimer count had median values of 34,000/µL and 19,235 µg FEU/L, respectively. The ELISA anti-PF4 antibody was positive in 18 samples. The overall mortality rate was 51% and was higher in cases of CNS thrombosis with intracerebral bleeding. CONCLUSION: Our case series shows that Brazilian VITT cases have similar clinical and laboratory profiles as demonstrated in the literature. Brazil has administered more than 300 million doses of COVID-19 vaccines (more than 110 million from ChAdOx1 nCoV-19). VITT seems to be a very rare but serious adverse event following COVID-19 immunization, especially adenoviral vector immunization.
