1 Introduction
Corona virus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, has become a global pandemic since 2020. Different kinds of vaccines were administrated all over the world to fight this disease. These SARS-CoV-2 vaccinations have been reported to cause immune thrombotic thrombocytopenic purpura (TTP) in the Western World [
1–
10]. As of April 2022, a total of 27 patients were reported to have TTP after receiving COVID-19 vaccines [
11]. These COVID-19 vaccines include Ad26.COV2-S (modified adenovirus) from Janssen [
1], BNT162b2 from Pfizer-BioNTech [
3–
5,
8], mRNA-1273 from Moderna [
12–
15], and ChAdOx1 nCov-19 from AstraZeneca-Oxford [
2]. They are either mRNA vaccines (BNT162b2 and mRNA-1273) or adenoviral-based vaccines (ChAdOx1 nCoV-19 and Ad26.COV2-S). However, whether inactivated vaccines could cause TTP is unknown. If so, whether the symptoms are different from those of TTPs mediated by mRNA- or adenoviral-based vaccines remain elusive. Here, two Chinese patients who developed TTP after being injected with inactivated vaccine (CoronaVac from Sinovac Biotech) were reported.
2 Case 1
A 23-year-old female received her second dose of CoronaVac, with the first dose injected 2 months before. She visited the doctor 3 days later complaining of dizziness and weakness on June 10, 2021. She had no special medical history except a resection of the pilonidal sinus. The patient denied history of hypertension, diabetes, nor coronary atherosclerotic heart disease. Blood tests showed white blood cells (WBCs) of 7.4 (4 × 109–10 × 109/L), hemoglobin (Hb) of 87 (120–160 g/L), and platelets of 22 (100 × 109–300 × 109/L). Bone marrow smears showed hyperproliferation of megakaryocytes with over 100 and various sizes of erythrocytes. On day 9, the platelet count and Hb level decreased to 12 × 109/L and 63 g/L, respectively. Scattered petechiae and purpuras were observed (Fig.1). Lactate dehydrogenase (LDH) and α-hydroxybutyrate dehydrogenase (α-HBDH) increased to 974 (72–182 U/L) and 777 (0–248 U/L), respectively. Other biochemical indices, including alanine aminotransferase, aspartate transaminase, creatine (Cr), uric acid (UA), and antinuclear antibody, and urine test were normal at that time. Nasopharyngeal SARS-Cov-2 PCR test was negative. Dexamethasone and intravenous immunoglobulin were added, and platelet transfusion was performed. On day 13, the patient’s body temperature reached 38.0 °C. Peripheral blood smears displayed 4.2% schistocytes (Fig.1). Laboratory parameters were deteriorating as follows: platelet count of 4 × 109/L, Hb of 50 g/L, D-dimer of 3.4 (0–1 μg/mL), fibrinogen degradation product (FDP) of 7.6 ( < 5 μg/mL), LDH of 2181 U/L, indirect bilirubin of 32.4 (1.7–10.2 μmol/L), direct bilirubin of 15.6 (0–5.1 μmol/L), Cr of 127.3 (41–73 μmol/L), UA of 549 (143–339 μmol/L), urine protein of ++ , urine occult blood of ++++, serum myoglobin of 195.6 (25–58 ng/mL), and serum troponin T of 0.123 (0–0.014 ng/mL). The patient developed aphasia on day 14. Antiplatelet factor 4-IgG was negative. A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) was 0 IU/mL, and its inhibitory antibodies were positive. The diagnosis of TTP was confirmed, and then glucocorticoids and plasma exchange were introduced. The product of plasma exchange was dark brown (Fig.1i). The color gradually turned lighter after several rounds of plasma exchange (Fig.1ii and 1Ciii). Soy sauce-like urine became normal (Fig.1i and 1Dii). In the following days, the platelet count and clinical condition improved. Rituximab was applied at 375 mg/m2 per week. Fig.1–Fig.1 shows the treatment protocol and the changes in blood cell count, coagulation index (D-dimer and FDP), hemolytic tests (LDH, α-HBDH, and bilirubin), and renal functions (UA and Cr). The level of ADAMTS13 antigen reached normal, and inhibitory ADAMTS13-antibodies became negative on day 153. As of November 9, 2023, the patient was still in the process of remission, with WBC of 7.8 × 109/L, Hb of 138 g/L, platelet count of 401 × 109/L, LDH of 172 U/L, indirect bilirubin of 4 μmol/L, direct bilirubin of 6.3 μmol/L, Cr of 65 μmol/L, and UA of 246 μmol/L.
3 Case 2
A 45-year-old female patient who received the second dose of CoronaVac (first dose was injected two months before) on March 19, 2021, visited a local hospital complaining of fever and muscle soreness for 5 days. Her body temperature reached 39.5 °C. The patient denied having special medical history, including hypertension, diabetes, and coronary atherosclerosis. Hematological abnormalities were found as follows: WBC of 7.18 × 109/L, Hb of 124 g/L, platelet count of 93 × 109/L, Cr of 223 μmol/L, UA of 311 μmol/L, LDH of 441 U/L, D-dimer of 9.28 μg/mL, and FDP of 35.62 μg/mL. Urine test showed protein ++ . Nasopharyngeal SARS-Cov-2 PCR test was negative. The patient quickly developed acute renal failure with Cr of 726 μmol/L, anemia with Hb of 71 g/L, and thrombocytopenia with platelet count of 15 × 109/L (Fig.2). Fragmented red cells were not found in the peripheral blood smear at that time. Hemorrhagic fever with renal syndrome (HFRS) was suspected, and special tests for hantavirus were ordered. The patient was transferred to the intensive care unit, and she received sustained hemodialysis and red blood transfusion. However, the condition did not improve, and on day 10, the patient developed coma. Brain MRI scan showed multiple cerebral infarctions in the bilateral frontal and parietal lobes. Then, severe fever with thrombocytopenia syndrome (SFTS) was suspected, and examinations for neobunia were ordered. On day 14, the blood results deteriorated, with WBC of 14.98 × 109/L, Hb of 53 g/L, platelet count of 9 × 109/L, and Cr of 446 μmol/L (hemodialysis every day). Then, platelet transfusion was performed. Several days later, the diagnosis of HFRS and SFTS was ruled out on the basis of the negative results of RNA sequencing and antibodies against hantavirus and neobunia virus. A total of 11.7% schistocytes were found in the peripheral blood smears at this time. Thus, TTP was considered, and serum ADAMTS13 test was ordered. Fresh frozen plasma was transfused several times, and the platelet count increased. Finally, the laboratory result of < 5% ADAMTS13 level confirmed the diagnosis of TTP. In the following days, the patient received seven rounds of plasma exchange and glucocorticoid administration. During this treatment, the patient suffered from retroperitoneal hemorrhage. The condition was ameliorated after surgical intervention. After two sessions of plasma exchanges, the patient’s consciousness was recovered, and the platelet count reached normal level. On day 30, the patient achieved complete remission except for mild anemia (Fig.2). The patient was still in good condition without any uncomfortableness as of November 9th, 2023. The blood test results on October 24th, 2023, showed WBC of 4.68 × 109/L, Hb of 134 g/L, platelet count of 164 × 109/L, LDH of 139 U/L, indirect bilirubin of 6.6 μmol/L, direct bilirubin of 3.4 μmol/L, Cr of 76.9 μmol/L, and UA of 283.26 μmol/L.
4 Series of cases
The clinical data of adult patients with TTP from 14 hospitals in Nanjing area from January 2019, to the end of December 2022, were collected and analyzed. Considering that the first acute episode of TTP mostly occurs during adulthood (90% of all TTP cases) [
16], data from children’s hospitals were not collected in the present study. The number of patients with TTP was 12 in 2019 (11 newly-diagnosed and one relapsed), six in 2020 (all newly diagnosed), 16 in 2021 (all newly diagnosed), and 19 in 2022 (17 newly diagnosed and two relapsed, Tab.1). Approximately 9.491 million residents are living in Nanjing area. Thus, the incidence of new TTP cases (per million population) was 1.159 in 2019, 0.632 in 2020, 1.686 in 2021, and 1.791 in 2022. The patients with TTP diagnosed in 2019 and 2020 did not receive any COVID-19 vaccine. Most patients with TTP newly diagnosed in 2021 and 2022 could not provide a confirmed history of COVID-19 vaccine injection. A total of 2/12, 1/6, 8/16, and 6/19 patients died in 2019, 2020, 2021, and 2022, respectively (Tab.1).
5 Discussion
Immune TTP, characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and diffuse microthrombus formation followed by ischemic end-organ lesions, is a rare but life-threatening bleeding disorder, where ADAMTS13, a protease cleaving von Willebrand factor (vWF), is relatively inadequate due to autoimmune factors [
17]. ADAMTS13 deficiency induces the accumulation of ultrahigh-molecular-weight multimers of vWF, leading to platelet aggregation and thrombosis.
Immune TTP is often triggered by some kinds of pathogenic microorganisms or their vaccines [
18,
19], which share a common epitope or common antigen with ADAMTS13. The specific antibody produced after B cell sensitization cross-reacts with ADAMTS13 and destroys it. Dozens of case reports about TTP diagnosed after COVID-19 vaccines have been published. However, those COVID-19 vaccines were based on either mRNA or adenoviral vector. Whether inactivated vaccines could cause TTP and whether the symptoms in TTP mediated by inactivated vaccines are different from previously published cases are unknown. Here, two Chinese cases of TTP after CoronaVac injection were reported. To the authors’ knowledge, this report is the first report about inactivated vaccine (CoronaVac)-associated TTP. Although billions of people received CoronaVac injections, the reports about TTP are rare, may be because inactivated vaccines cause milder immune responses than other types of vaccines. A head-to-head comparison of the immunogenicity of BNT162b2 and CoronaVac COVID-19 vaccines showed that vaccination with CoronaVac induced weaker humoral responses than BNT162b2 [
20]. CoronaVac has a relatively safe profile with mild untoward reactions only [
21].
In this study, the two cases remained symptom-free for approximately 2 months following the first dose of COVID-19 vaccine but developed TTP shortly after the second doses (about 3–5 days). This observation is consistent with a report by Sissa
et al., in which a relapse of TTP occurred following the second dose of BNT162b2 vaccine [
5]. It is likely that the first vaccination sensitizes the immune system, whereas the second shot induces TTP by bursting the immune reactions. By contrast, a higher frequency of TTP was observed following the first shot in mRNA-based vaccines than in inactivated vaccines. Picod [
9] reported 10 cases of TTP occurring within 30 days after combined vaccination of mRNA- and adenoviral vector-based vaccines. Eight out of the 10 cases (80%) developed TTP after the first dose, whereas the remaining two (20%) developed TTP after the second dose. Thus, mRNA- or adenoviral vector-based vaccines may trigger faster immune response than inactivated ones.
Five symptoms, including fever, thrombocytopenia, microangiopathic hemolytic anemia characterized by schistocytes, neurological symptoms, and renal insufficiency, were used to define TTP [
16]. Thus, the corresponding clinical tests used to evaluate these symptoms, such as blood smear, whole blood count, blood biochemistry (LDH, bilirubin, Cr, BUN, and UA), and urine tests, contribute to the diagnosis of TTP. However, the most important test to confirm TTP is the measurement of ADAMTS13 antigen and activity and its inhibitory antibodies. The symptoms of TTP often overlap with those of other types of thrombocytopenic diseases. TTP is often misdiagnosed as Evan’s syndrome, HFRS, or SFTS. The misdiagnoses of Evan’s syndrome in case 1 and HFRS or SFTS in case 2 led to an administration of intravenous immunoglobulin and even platelet transfusion, which deteriorated the disease. Obtaining the final correct diagnosis took half a month. The treatment of TTP includes plasma exchange, glucocorticoids, rituximab, caplacizumab, or recombinant ADAMTS13. Plasma exchange is the standard first-line care, which removes “evil humors” and replenishes “something good.” Both cases achieved complete remission after several sessions of plasma exchange and immune suppression. This finding suggests that COVID-19 vaccine-related acquired TTP, similar to other forms of acquired TTP, could be treated by plasma exchange and immunosuppression.
In January 2020, a pneumonia caused by the new coronavirus broke out. On February 11, 2020, the Director General of the World Health Organization, Tedros Adhanom Ghebreyesus, announced in Geneva, Switzerland, that the new coronavirus-infected pneumonia was named COVID-19. Since January 25, 2020, China has been in a state of partial lockdown with massive social distancing measurements launched. Since February 2020, Chinese scientists have been working to develop COVID-19 vaccines. On December 11, 2020, the Jiangsu Health Commission granted the emergency use (trial) plan of the novel coronavirus vaccine. Since January 2021, medical workers became the first group to receive the vaccine injections in Nanjing area, Jiangsu Province. As of December 8, 2022, more than 95% of residents < 60 years old and at least 90% of residents > 60 years old received vaccine injection in Nanjing area. From February 2020 to December 2022, only few sporadic COVID-19 cases were reported in Nanjing area. A time axis illustrating the major COVID-19 events is listed in Fig.3.
TTP is a rare hematologic disease with an average annual prevalence of about 10 cases/million people and an annual incidence of about one new case/million people [
16]. The incidence in 2019 is consistent with literature [
16] suggesting the basic prevalence of TTP in Nanjing area. However, the incidence decreased in 2020, followed by an increase in 2021 and 2022. Considering TTP is closely related to infection, the drop in incidence may be the result of social distancing measures, such as quarantine and lockdown in the area (Fig.3), which prevented the spread of respiratory diseases caused by SARS-CoV-2 or other pathogens. With the massive vaccination initiative being launched in China in 2021, the majority of the population became vaccinated by the end of 2022 (Fig.3). Thus, it is reasonable to speculate that the increase in incidence in 2021 and 2022 may be caused by injection of COVID-19 vaccines. Although most patients with TTP newly diagnosed in 2021 and 2022 could not provide a confirmed history of COVID-19 vaccine injection, 90%–95% of residents received vaccine injection in Nanjing area during this period. The incidence of new TTP cases (per million population) was 1.159 in 2019, 0.632 in 2020, 1.686 in 2021, and 1.791 in 2022 (see above). Thus, the estimated incidence of TTP in the population receiving inactivated COVID-19 vaccine is speculated to be 1.106 ((1.686 + 1.791)/2–0.632) per million.
In conclusion, two cases of acquired TTP associated with an inactivated COVID-19 vaccine, CoronaVac, in the Chinese population were reported, and the incidence of TTP following vaccine injection in Nanjing area was analyzed. To the authors’ knowledge, this report is the first report about TTP related to inactivated COVID-19 vaccine. Timely plasma exchange is vital for COVID-19 related TTP.
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