Do Patients with a Family or Personal History of Venous Thromboembolism have an Increased Risk of Recurrence?

2021 ◽  
Author(s):  
Jonas Florin ◽  
Odile Stalder ◽  
Christine Baumgartner ◽  
Marie Méan ◽  
Nicolas Rodondi ◽  
...  
Keyword(s):  
Venous Thromboembolism ◽  
Recurrence Risk ◽  
Personal History ◽  
Dose Effect ◽  
Risk Of Recurrence ◽  
Increased Risk ◽  
History Of ◽  
Risk Factors For Recurrence ◽  
Recurrent Vte ◽  
Observation Period

Abstract Background A family (FH) and personal history (PH) of venous thromboembolism (VTE) are commonly evaluated risk factors for recurrence. We examined the association between FH/PH of VTE and the risk of recurrence and whether a stronger history status (i.e., both FH/PH vs. no FH/PH) carries an increased recurrence risk. Methods We prospectively followed 813 patients aged ≥ 65 years with acute VTE from 9 Swiss hospitals. We classified patients into four groups: no FH/PH, FH only, PH only, and both FH/PH. The primary outcome was recurrent VTE during the full observation period. We examined the association between FH/PH status and the time to VTE recurrence using competing risk regression, adjusting for confounders and periods of anticoagulation. Results Of 813 patients with VTE, 59% had no FH/PH, 11% a FH only, 24% a PH only, and 7% had both a FH and PH of VTE. Overall, 105 patients had recurrent VTE during the full observation period. After adjustment, patients with a FH only (subhazard ratio [SHR] 0.8, 95% confidence interval [CI] 0.4–1.7), PH only (SHR 1.5, 95% CI 0.9–2.5), and both FH/PH (SHR 1.4, 95% CI 0.6–3.1) did not have an increased risk of recurrent VTE compared with those without FH/PH. When we considered the period after the completion of initial anticoagulation only, the results were similar. Conclusion Our findings indicate that in patients with acute VTE, a FH and/or PH of VTE does not convey an increased risk of recurrent VTE. In particular, we did not find a “dose–effect” relationship between FH/PH status and VTE recurrence.

scholarly journals Association Between Anticoagulation Outcomes and Venous Thromboembolism History in Chronic Thromboembolic Pulmonary Hypertension

2021 ◽  
Vol 8 ◽  
Author(s):  
Yong-Jian Zhu ◽  
Yu-Ping Zhou ◽  
Yun-Peng Wei ◽  
Xi-Qi Xu ◽  
Xin-Xin Yan ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Venous Thromboembolism ◽  
Chronic Thromboembolic Pulmonary Hypertension ◽  
Prior History ◽  
Anticoagulation Treatment ◽  
Increased Risk ◽  
Thromboembolic Pulmonary Hypertension ◽  
History Of ◽  
Recurrent Vte ◽  
Potential Factors

Background: The association between anticoagulation outcomes and prior history of venous thromboembolism (VTE) in chronic thromboembolic pulmonary hypertension (CTEPH) has not been established. This study aimed to compare the efficacy and safety of anticoagulation treatment in CTEPH patients with and without prior history of VTE.Methods: A total of 333 CTEPH patients prescribed anticoagulants were retrospectively included from May 2013 to April 2019. The clinical characteristics were collected at their first admission. Incidental recurrent VTE and clinically relevant bleeding were recorded during follow-up. The Cox proportional regression models were used to identify potential factors associated with recurrent VTE and clinically relevant bleeding.Results: Seventy patients (21%) without a prior history of VTE did not experience recurrent VTE during anticoagulation. Compared to CTEPH patients without a prior history of VTE, those with a prior history of VTE had an increased risk of recurrent VTE [2.27/100 person-year vs. 0/100 person-year; hazard ratio (HR), 8.92; 95% confidence interval (CI), 1.18–1142.00; P = 0.029] but a similar risk of clinically relevant bleeding (3.90/100 person-year vs. 4.59/100 person-year; HR, 0.83; 95% CI, 0.38–1.78; P = 0.623). Multivariate Cox analyses suggested that a prior history of VTE and interruption of anticoagulation treatments were significantly associated with an increased risk of recurrent VTE, while anemia and glucocorticoid use were significantly associated with a higher risk of clinically relevant bleeding.Conclusions: This study is the first to reveal that a prior history of VTE significantly increases the risk of recurrent VTE in CTEPH patients during anticoagulation treatment. This finding should be further evaluated in prospective studies.

scholarly journals Venous thromboembolism and bleeding in a community setting

2009 ◽  
Vol 101 (05) ◽  
pp. 878-885 ◽  
Author(s):  
Joel Gore ◽  
George Reed ◽  
Darleen Lessard ◽  
Luigi Pacifico ◽  
Cathy Emery ◽  
...  
Keyword(s):  
Venous Thromboembolism ◽  
Total Mortality ◽  
Community Setting ◽  
Patient Characteristics ◽  
Recurrence Rates ◽  
Increased Risk ◽  
History Of ◽  
Recurrent Vte ◽  
The Impact

SummaryBleeding is the most frequent complication of antithrombotic therapy for venous thromboembolism (VTE). However, little attention has been paid to the impact of bleeding after VTE in the community setting. The purpose of this investigation was to describe the incidence rate of bleeding after VTE, to characterize patients most at risk for bleeding, and to assess the impact of bleeding on rates of recurrent VTE and all-cause mortality. The medical records of residents of the Worcester (MA, USA) metropolitan area diagnosed with ICD-9 codes consistent with potential VTE during 1999, 2001, and 2003 were individually validated and reviewed by trained data abstracters. Clinical characteristics, acute treatment, and outcomes (including VTE recurrence rates, bleeding rates, and mortality) over follow-up (up to 3 years maximum) were evaluated. Bleeding occurred in 228 (12%) of 1,897 patients with VTE during our follow-up. Of these, 115 (58.8%) had evidence of early bleeding occurring within 30 days of VTE diagnosis. Patient characteristics associated with bleeding included impaired renal function and recent trauma. Other than a history of prior VTE, the occurrence of bleeding was the strongest predictor of recurrent VTE (hazard ratio [HR] 2.18; 95% confidence interval [CI] 1.54–3.09) and was also a predictor of total mortality (HR 1.97; 95%CI 1.57–2.47). The occur-rence of bleeding following VTE is associated with an increased risk of recurrent VTE and mortality. Future study of antithrombotic strategies for VTE should be informed by this finding. Advances that result in decreased bleeding rates may paradoxically decrease the risk of VTE recurrence.

scholarly journals A systematic review of antithrombotic treatment of venous thromboembolism in patients with myeloproliferative neoplasms

2021 ◽  
Vol 5 (1) ◽  
pp. 113-121
Author(s):  
Eva N. Hamulyák ◽  
Joost G. Daams ◽  
Frank W. G. Leebeek ◽  
Bart J. Biemond ◽  
Peter A. W. te Boekhorst ◽  
...  
Keyword(s):  
Systematic Review ◽  
Venous Thromboembolism ◽  
Observational Studies ◽  
Randomized Trials ◽  
Myeloproliferative Neoplasms ◽  
Recurrence Risk ◽  
Antithrombotic Treatment ◽  
Statistical Heterogeneity ◽  
History Of ◽  
Recurrent Vte

Abstract Patients with myeloproliferative neoplasms (MPNs), polycythemia vera, essential thrombocythemia, and primary myelofibrosis, have an increased risk of thrombosis. Risk of recurrent thrombosis can be reduced with antithrombotic therapy and/or cytoreduction, but the optimal long-term management in patients with MPN with a history of venous thromboembolism (VTE) is unknown, and clinical practice is heterogeneous. We performed a systematic review and meta-analysis of randomized trials and observational studies evaluating anticoagulant and/or antiplatelet therapy, with or without cytoreduction, in MPN patients with a history of VTE. A total of 5675 unique citations were screened for eligibility. No randomized trials were identified. Ten observational studies involving 1295 patients with MPN were included in the analysis. Overall, 23% had an arterial or recurrent venous thrombotic event on follow-up. The recurrence risk was lowest for patients on oral anticoagulation plus cytoreduction (16%); 55 of 313 (18%) with vitamin K antagonists (VKA) and 5 of 63 (8%) with direct oral anticoagulants (DOACs). In 746 analyzed patients, the risk of recurrent VTE ranged up to 33% (median 13%) and was low in 63 DOAC plus cytoreduction-treated patients (3.2%). All types of antithrombotic treatments were associated with a lower risk of recurrent VTE when combined with cytoreduction. Most studies had a high risk of bias, whereas clinical and statistical heterogeneity led to inconsistent and imprecise findings. In summary, evidence on the optimal antithrombotic treatment of VTE in patients with MPN is based on observational studies only with low certainty for all strategies. Our data suggest that a combination of anticoagulation and cytoreduction may provide the lowest recurrence risk.

Clinical scores to predict recurrence risk of venous thromboembolism

2012 ◽  
Vol 108 (12) ◽  
pp. 1061-1064 ◽  
Author(s):  
Sabine Eichinger ◽  
Paul Kyrle
Keyword(s):  
Venous Thromboembolism ◽  
Clinical Importance ◽  
Case Fatality ◽  
Recurrence Risk ◽  
Daily Routine ◽  
Activation Markers ◽  
Thrombotic Risk ◽  
Risk Of Recurrence ◽  
Clinical Patient ◽  
Recurrent Vte

SummaryVenous thromboembolism (VTE) is a common and chronic disease with a considerable risk of recurrence. Patients with unprovoked (in the absence of a transient risk factor) VTE have a recurrence risk as high as 30% within five years after cessation of anticoagulation. Depending on patient selection the case-fatality rate of recurrence ranges between 3.6%-10%. Thus, indefinite anticoagulation treatment should be considered in these patients. However, anticoagulation confers a considerable risk of bleeding (fatal bleedings 0.1%–0.5%/year). It is therefore of utmost clinical importance to identify those patients, who will not benefit from indefinite anticoagulation, i.e. patients, in whom the bleeding risk during anticoagulant treatment is higher than the risk of recurrence. Several attempts to discriminate patients with a high from those with a low risk of recurrence including screening for acquired and inherited thrombotic risk factors or measurement of coagulation activation markers have either failed (thrombophilia screening) or were of moderate success (stratification according to D-dimer only). A novel approach for assessing risk of recurrent VTE consists of linking clinical patient characteristics with laboratory testing. Several such scoring models which can be used to assess the risk of recurrent VTE have been developed and await prospective validation before they can be applied in daily routine care. The aim of this report is to describe currently available scoring systems in more detail.

Individually Tailored Prophylaxis Using a Risk Score for the Management of Pregnant Women with Increased Risk of Venous Thromboembolism

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 889-889
Author(s):  
Yesim G. Dargaud ◽  
Lucia Rugeri ◽  
Chloe Fleury ◽  
Helene Desmurs Clavel ◽  
Jacques Ninet ◽  
...  
Keyword(s):  
Pulmonary Embolism ◽  
Venous Thromboembolism ◽  
High Risk ◽  
Prospective Study ◽  
Pregnant Women ◽  
Risk Score ◽  
Personal History ◽  
Vein Thrombosis ◽  
Increased Risk ◽  
History Of

Abstract Patients with thrombophilia and/or a history of venous thromboembolism (VTE) exhibit a high risk of thrombosis during pregnancy. A risk score for pregnancies with increased risk of VTE was previously described by our group (1,2). The present work reports the results of a prospective study, evaluating the efficacy and the safety of the prophylaxis strategy based on the same risk score, in 542 pregnancies at high risk of VTE, managed between 2005 and 2015 in Lyon University Hospitals. Among 445 patients included in the study, 26 had several pregnancies during the study period. The mean age of the study population was 33±4.8 years, 132 women (29.7%) were older than 35 years. Fifty three women had a BMI of 30 or over and 61 were smokers. Among these 445 patients, 279 had a personal history of VTE (62.7%), 299 patients (67.2%) had a thrombophilia marker and 131 (29.4%) thrombophilic women had a personal history of VTE. During pregnancy, patients were assigned to one of three prophylaxis strategies according to the risk scoring system. Compression stockings were worn by the majority of the patients throughout the pregnancy and during the postpartum. In antepartum, LMWH prophylaxis was prescribed to 64.5% of patients with high risk of VTE. Among them, 34.4% were treated in the third trimester only and 30.1% were treated throughout pregnancy. In postpartum, all patients received low molecular weight heparin (LMWH) prophylaxis for at least 6 weeks. In this cohort, two antepartum-related VTE (0.37%) and four postpartum-related VTE (0.73%) occurred. One of the ante-partum related VTE was occurred in a patient who was on LMWH prophylaxis with enoxaparin 40mg/day for a personal history of spontaneous pulmonary embolism and homozygous prothrombin G20210A mutation. Despite well conducted LMWH prophylaxis, the patient had a distal deep vein thrombosis (DVT) at week 28. The second VTE was a proximal DVT during a bed resting in the eighth month of pregnancy in a patient with heterozygous FV Leiden mutation and a history of proximal DVT. According to the risk score, LMWH prophylaxis was required during bed-resting but it was not prescribed by the obstetrician. Among four postpartum-related VTE, 3 occurred after the 6 weeks of LMWH prophylaxis, between weeks 8 and 12 of the postpartum period and one was a ovarian vein thrombosis. No case of pulmonary embolism was observed during the study period. The rate of bleeding was 0.37%, no serious bleeding requiring transfusions or surgery was occurred during the study period. There was no evidence of heparin-induced thrombocytopenia or osteoporosis. The use of a risk score may provide a rational decision process to implement safe and effective antepartum thromboprophylaxis in pregnant women at high risk of VTE Dargaud, Y., Rugeri, L., Ninet, J., Negrier, C. & Trzeciak, M.C. Management of pregnant women with increased risk of venous thrombosis. International Journal of Gynaecology and Obstetrics 2005, 90,203-207 Dargaud, Y., Rugeri, L., Vergnes MC, Arnuti B, Miranda P, Negrier, C., Ninet, J., Trzeciak, M.C. A risk score for the management of pregnant women with increased risk of venous thrombomebolism: a multicenter prospective study. Br J Haematol 2009;145:825-35 Disclosures No relevant conflicts of interest to declare.

Incidence and Risk Factors of Venous Thromboembolism in Patients with Multiple Myeloma Receiving Immunomodulatory Agents

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2624-2624 ◽  
Author(s):  
Miriam Kimpton ◽  
Ryan Buyting ◽  
Daniel J Corsi ◽  
Natasha Rupani ◽  
Marc Carrier ◽  
...  
Keyword(s):  
Risk Factors ◽  
Multiple Myeloma ◽  
Venous Thromboembolism ◽  
Previous History ◽  
Patient Characteristics ◽  
Hematologic Malignancies ◽  
Personal History ◽  
Immunomodulatory Agents ◽  
Increased Risk ◽  
History Of

Abstract Multiple myeloma (MM) is an incurable plasma cell disorder representing 10% of all hematologic malignancies. Cancer is a known risk factor for venous thromboembolism (VTE). Patients with MM are at a particularly high risk of developing VTE owing to patient characteristics (e.g. previous history of VTE), disease characteristics, and treatment characteristics including use of the immunomodulatory agents (IMIDs). Unfortunately, standard criteria to identify the patients most at risk for developing VTE in MM while receiving IMIDs are unknown. We sought to assess the incidence of VTE and its associated risk factors in MM patients receiving IMID therapy. A retrospective cohort study including 1680 consecutive patients with multiple myeloma treated at our centre between January 01, 1995 and January 26, 2016 was conducted. The annual incidence of VTE on immunomodulatory agents including thalidomide, lenalidomide, and pomalidomide was derived. Univariate incidence ratio analyses of VTE for different risk factors was performed including: previous history of VTE, concomitant use of dexamethasone, and ≥/< 6 months after IMID initiation. A total of 309 MM patients treated with an immunomodulatory agent were identified. Nineteen patients were excluded (incomplete data, lost to follow). Of the remaining 290 patients, the mean age was 67.9 and 42.4% were female. Twenty-seven VTE events were recorded. The overall risk ratio was 6.1 for the development of VTE. Patients with a personal history of VTE had an increased risk of suffering a VTE while on IMID therapy (IRR 5.4; CI, 1.9-13.6). The time from the initiation of the IMID therapy (less than 6 months) also increased the risk of developing a VTE (IRR 51.7; CI,19.4-160.1). The concomitant use of dexamethasone was not associated with a statistically significant increased risk (IRR 1.7; CI, 0.3-69.5). Incidence risk ratios for these risk factors are depicted in Table 1. Our results suggest that a personal history of VTE and the time from the initiation of the IMID (less than 6 months) are associated with an increased risk of VTE in MM patients receiving IMID therapy. This may be helpful in determining which multiple myeloma patients treated with an IMID agent warrant more aggressive thromboprophylaxis. Further prospective studies are needed to determine the optimal agent, intensity, and duration of thromboprophylaxis in patients with MM on IMID therapy. Disclosures McCurdy: Celgene: Honoraria.

Predicting the risk of recurrent venous thromboembolism

2013 ◽  
Vol 33 (03) ◽  
pp. 201-209 ◽  
Author(s):  
L. Eischer ◽  
P. A. Kyrle
Keyword(s):  
Venous Thromboembolism ◽  
Vena Cava ◽  
Factor V Leiden ◽  
Recurrence Risk ◽  
Clotting Factor ◽  
Factor V ◽  
Vein Thrombosis ◽  
Increased Risk ◽  
Thrombophilia Screening ◽  
Recurrent Vte

SummaryVenous thromboembolism (VTE) is a disease, which often recurs. The recurrence risk is highest in patients with unprovoked proximal deep-vein thrombosis (VT) or pulmonary embolism. Men have a higher risk than women. The risk is low in patients with VTE related to a temporary risk factor such as surgery or estrogen use. Other risk factors include overweight, post-thrombotic syndrome, history of VTE, residual VT or a vena cava filter.Both factor V Leiden and the prothrombin mutation confer a negligible increase in recurrence risk. High clotting factor levels, deficiency of a natural coagulation inhibitor, or hyperhomocysteinaemia are also associated with an increased risk. Reasons why routine laboratory thrombophilia screening however is no longer warranted are addressed in this article. Prediction rules combining clinical characteristics and coagulation assays have recently been developed. One such model, the Vienna Prediction Model, allows predicting recurrent VTE on the basis of VTE location, sex and D-dimer. This article describes strategies to distinguish between patients with high risk of recurrent VTE from those with a lower risk, who might not benefit from long-term antithrombotic therapy.

Decreased anticoagulant response to tissue factor pathway inhibitor in patients with venous thromboembolism and otherwise no evidence of hereditary or acquired thrombophilia

2004 ◽  
Vol 91 (01) ◽  
pp. 80-86 ◽  
Author(s):  
Brigitte Piccapietra ◽  
Johanna Boersma ◽  
Joerg Fehr ◽  
Thomas Bombeli
Keyword(s):  
Venous Thromboembolism ◽  
Venous Thrombosis ◽  
Mean Value ◽  
Healthy Controls ◽  
Crude Odds Ratio ◽  
Sensitivity Ratio ◽  
Increased Risk ◽  
History Of ◽  
Anticoagulant Response ◽  
Acquired Thrombophilia

SummaryNo relevant deficiency of TFPI or genetic polymorphisms could thus far consistently be associated with venous thromboembolism. We hypothesized that the substrates of the TFPI protein, including FVII or FX (rather than the protein itself) could induce a hypercoagulable state. We created a novel TF-based clotting assay that evaluated the anticoagulant response to exogenously added recombinant TFPI. The response to TFPI was expressed as the ratio of the clotting time with and without TFPI. By using 118 healthy controls, we established a reference range between 1.31 and 1.93 (mean value ± 2 standard deviations (SD), 1.62 ± 0.31). We then evaluated samples from 120 patients with a history of venous thromboembolism but no evidence of hereditary and acquired thrombophilia. The range of the patients’ ratios was significantly (P < 0.001) lower, falling between 1.2 and 1.78 (mean value ± 2 SD, 1.49 ± 0.29). Of the 120 patients, 39 (32.5%) had a TFPI sensitivity ratio below the 10th percentile of the controls, compared with 11 (9.3%) of the healthy controls. The crude odds ratio for venous thrombosis for subjects with a TFPI sensitivity ratio below the 10th percentile was 13 (95% CI; range, 3.1 to 54.9) compared with those with a ratio above 1.8 (90th percentile). Patients with idiopathic thromboembolism did not have a decreased TFPI sensitivity ratio more often than patients with thrombosis with a circumstantial risk factor. Based on these results, a reduced response to TFPI may lead to an increased risk of venous thrombosis.

scholarly journals Clinical and Imaging Predictors of Recurrent Ischemic Stroke: A Systematic Review and Meta-Analysis

2018 ◽  
Vol 45 (5-6) ◽  
pp. 279-287 ◽  
Author(s):  
Frans Kauw ◽  
Richard A.P. Takx ◽  
Hugo W.A.M. de Jong ◽  
Birgitta K. Velthuis ◽  
L. Jaap Kappelle ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Lower Risk ◽  
Meta Analysis ◽  
Cochrane Library ◽  
Large Artery ◽  
Cortical Lesions ◽  
Level Of Evidence ◽  
Risk Of Recurrence ◽  
Increased Risk ◽  
History Of

Background: Predictors of recurrent ischemic stroke are less well known in patients with a recent ischemic stroke than in patients with transient ischemic attack (TIA). We identified clinical and radiological factors for predicting recurrent ischemic stroke in patients with recent ischemic stroke. Methods: A systematic search in PubMed, Embase, Cochrane Library, and CINAHL was performed with the terms “ischemic stroke,” “predictors/determinants,” and “recurrence.” Quality assessment of the articles was performed and the level of evidence was graded for the articles included for the meta-analysis. Pooled risk ratios (RR) and heterogeneity (I2) were calculated using inverse variance random effects models. Results: Ten articles with high-quality results were identified for meta-analysis. Past medical history of stroke or TIA was a predictor of recurrent ischemic stroke (pooled RR 2.5, 95% CI 2.1–3.1). Small vessel strokes were associated with a lower risk of recurrence than large vessel strokes (pooled RR 0.3, 95% CI 0.1–0.7). Patients with stroke of an undetermined cause had a lower risk of recurrence than patients with large artery atherosclerosis (pooled RR 0.5, 95% CI 0.2–1.1). We found no studies using CT or ultrasound for the prediction of recurrent ischemic stroke. The following MRI findings were predictors of recurrent ischemic stroke: multiple lesions (pooled RR 1.7, 95% CI 1.5–2.0), multiple stage lesions (pooled RR 4.1, 95% CI 3.1–5.5), multiple territory lesions (pooled RR 2.9, 95% CI 2.0–4.2), chronic infarcts (pooled RR 1.5, 95% CI 1.2–1.9), and isolated cortical lesions (pooled RR 2.2, 95% CI 1.5–3.2). Conclusions: In patients with a recent ischemic stroke, a history of stroke or TIA and the subtype large artery atherosclerosis are associated with an increased risk of recurrent ischemic stroke. Predictors evaluated with MRI include multiple ischemic changes and isolated cortical lesions. Predictors of recurrent ischemic stroke concerning CT or ultrasound have not been published.

Abstract 524: Influenza Vaccination Reduces The Risk Of Venous Thromboembolism

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Tienan Zhu ◽  
Laure Carcaillon ◽  
Isabelle Martinez ◽  
Jean-Pierre Cambou ◽  
Xavier Kyndt ◽  
...  
Keyword(s):  
Venous Thromboembolism ◽  
Protective Effect ◽  
Influenza Vaccination ◽  
Varicose Veins ◽  
Personal History ◽  
Protective Effects ◽  
Crude Odds Ratio ◽  
Confounding Variables ◽  
History Of

It is widely accepted that influenza vaccination reduces the risk of cardiovascular events in patients with coronary artery diseases. However, no information is available concerning the role of influenza vaccination in venous thromboembolism (VTE). Methods: A case-control study was conducted in 727 cases and 727 age and sex-matched controls from 11 centers in France (the FARIVE study). Cases were patients with a first documented episode of VTE and without any personal history of cancer within the last 5 years; controls were recruited in the same hospital and had no personal history of venous or arterial thrombosis. Results: Overall, 202 (28.2%) of cases and 233 (32.1%) of controls had influenza vaccination during the previous 12 months at the time of recruitment. Information was not available for only 12 subjects out of 1454. The crude odds ratio (OR) for VTE associated with influenza vaccination was 0.76 (95% CI 0.58–0.99). After adjustment for potential confounding variables (age, sex, inclusion date, BMI, educational levels and varicose veins), the OR for VTE associated with vaccination was 0.74 (95% CI 0.57–0.97). The protective effect of vaccination toward VTE was higher in the population below 52 years (median of age), with an OR of 0.52 (95% CI 0.32–0.85). In women below the age of 51, the crude OR for VTE associated with influenza vaccination was 0.50 (95% CI 0.24–1.05) and was significant after adjustment for confounding variables including oral contraceptives, with an OR of 0.41 (95% CI 0.19–0.92). The protective effect of vaccination was similar for different types of VTE (DVT or PE). There was no statistical differences in the protective effects when we compared provoked with unprovoked VTE events. Conclusion: This is the first study that demonstrates a protective effect of influenza vaccination in VTE. In vitro influenza induces activation of coagulation and inflammation but we cannot rule out that the protective effect of influenza vaccination was due to other unknown mechanisms, as the protective effect was similar within the different seasons of the year. Influenza vaccination may reduce the risk of VTE by 26%. This relationship between influenza vaccination and VTE and its underlying mechanism still need to be analyzed and confirmed in further studies.

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