Tag: blood clots

Categories : COVIDTags :

Mechanism of AstraZeneca Blood Clotting Detailed in Study

On By ModernMedia
Red blood cells. CC0 Creative Commons

A new study into rare cases of blood clots in the brain with low platelets seen in some patients after vaccination has been published in the New England Journal of Medicine.

The research team behind the study were the first clinicians in the UK to spot the link between the Oxford/AstraZeneca vaccine and rare cases of blood clotting along with a low platelet count, before identifying the correct diagnostic test for the syndrome. They recommended the treatment approach which avoids the use of heparin, an anticoagulant typically used to treat normal blood clots.

The researchers detailed the cases of 23 patients, who all presented with thrombosis and thrombocytopenia after receiving the AstraZeneca vaccine, and none of whom had underlying conditions which would predispose them to blood clots.

The presence of the PF4 antibody (platelet factor 4) was detected in almost all cases (21 out of 23). In rare instances, these antibodies are triggered by the blood-thinning drug heparin, a syndrome known as heparin-induced thrombocytopenia (HIT). However, HIT was ruled out because none of the patients in this study received heparin.

The investigators therefore concluded that they were seeing a heparin-independent PF4-dependent syndrome in the setting of the AstraZeneca vaccine. They cautioned that this syndrome needs to be identified quickly if present, because its treatment is very different to that of blood clots with low platelet counts.

Co-author Professor Tom Solomon commented: “Although it is a very rare side effect, this issue of clots in the brain and elsewhere combined with blood abnormalities following COVID-19 immunization is extremely important. It is critical we understand the disease mechanisms so we can provide the best treatment for patients. Here at the University we are part of a national program collecting information on such patients.”

The researchers stressed that vaccination is still the key means to end the pandemic, and everyone should continue to receive a vaccine when offered one.

Source: Medical Xpress

Journal information: Marie Scully et al. Pathologic Antibodies to Platelet Factor 4 after ChAdOx1 nCoV-19 Vaccination, New England Journal of Medicine (2021). DOI: 10.1056/NEJMoa2105385

Categories : Injury & TraumaTags :

Positive Safety Evaluation for Tranexamic Acid

On By ModernMedia

A large meta-analysis upheld the safety of tranexamic acid (TXA), even at higher doses.

TXA is an antifibrinolytic agent with a short half-life that is used for bleeding prevention and treatment, as in causes of trauma with open wounds. Current TXA is applied with caution due to perceived increased risk of seizures, MI, and other thrombotic complications.

The meta-analysis looked at 216 randomised trials involving 125 550 participants. The investigators found that the incidence of thromboembolic events, which included venous thrombosis, pulmonary embolism, venous thromboembolism, myocardial infarction (MI) or ischaemia, and cerebral infarction or ischaemia, was 2.1% of people receiving IV TXA and a similar 2.0% of peers getting placebo or another control, which was a non-significant difference.

TXA’s safety was inconclusive in those with neurological conditions, who showed increased heterogeneity and asymmetry in funnel plots, according to Patrick Meybohm, MD, of University Hospital Wuerzburg in Germany, and colleagues.

The review confirmed that TXA was linked to a significant reduction in overall mortality and bleeding mortality, but not nonbleeding mortality.

“The results of this study suggest that use of intravenous TXA may have utility in all medical fields, with some uncertainty for patients with neurological conditions,” the investigators concluded.

“Notably, we did not detect any dose-dependent association of TEs [thromboembolic events],” they stated. The included studies had participants with IV TXA administration at doses ranging 0.5-5g or 10-100mg/kg.

“There is little doubt that when used appropriately in the various patient populations evaluated with randomized clinical trials, TXA is effective. However, reasonable questions about thrombotic complications remain,” wrote John Holcomb, MD, of University of Alabama at Birmingham, and colleagues, in an invited commentary.

“Further research must focus on how to identify, as early as possible, the patients most likely to benefit from administration of TXA,” they urged.

One limitation mentioned by the investigators was the inclusion trials that evaluated thromboembolic events without ultrasound, so asymptomatic cases may have been excluded. Furthermore, many studies did not provide much information on thrombosis prophylaxis.

For Holcomb’s group, study’s main caveat was that it included “a notably heterogeneous population”, including a range of demographics and clinical conditions. Since the pooled studies were not “clinically homogeneous”, they violated “one of the cardinal tenets of systematic reviews and meta-analyses.”

Source: MedPage Today

Journal information (primary article): Taeuber I, et al “Association of intravenous tranexamic acid with thromboembolic events and mortality: a systematic review, meta-analysis, and meta-regression” JAMA Surg 2021; DOI: 10.1001/jamasurg.2021.0884.

Journal information (commentary): Holcomb JB, et al “Tranexamic acid and safety in the right patient” JAMA Surg 2021; DOI: 10.1001/jamasurg.2021.0929.

Categories : COVIDTags :

US Hits Pause on J&J Vaccine

On By ModernMedia

Reacting to reports of potentially dangerous blood clots, the US is recommending a “pause” in immunisations with the single-dose Johnson & Johnson COVID vaccine in order to perform investigations.

The Centers for Disease Control and Prevention and the Food and Drug Administration said in a joint statement that they were investigating blood clots in six women that occurred 6 to 13 days after vaccination. The clots, seen in the sinuses of the brain, also had lowered platelet counts. This renders the use of heparin, the standard treatment for blood clots, potentially dangerous.

Out of 183.5 million vaccine doses administered in the US, over 6.8 million doses are the J&J vaccine — the overwhelming majority without serious side effects. The rest is made up by the two other authorised vaccines, from Moderna and Pfizer.

Use of the J&J shot will be paused in US federal distribution channels, including mass vaccination sites, with states and other providers being expected to follow.

CDC’s Advisory Committee on Immunization Practices will meet Wednesday to discuss the cases and the FDA has also launched an investigation into the cause of the clots and low platelet counts.

“Until that process is complete, we are recommending a pause in the use of this vaccine out of an abundance of caution,” Dr Anne Schuchat, principal deputy director of the CDC, and Dr Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a joint statement.

They recommend that people who received the J&J vaccine and are experiencing severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after receiving the jab contact their health care provider.

Officials say that they want to bring healthcare providers up to speed on the blood clot’s “unique treatment” .

Meanwhile, Johnson & Johnson had said it was aware of the blood clot reports, but no association with its vaccine had been established.

“We are aware that thromboembolic events including those with thrombocytopenia have been reported with Covid-19 vaccines,” the company said in a statement. “At present, no clear causal relationship has been established between these rare events and the Janssen Covid-19 vaccine.”

In late February, the FDA  granted emergency use authorisation to the J&J vaccine, with hopes that its single-dose and relatively simple storage requirements would speed vaccinations across the country. However, only a fraction of the vaccines administered in the US are the J&J shot. The company has been beset by production delays and manufacturing errors at a contractor’s plant. 

The pharmaceutical company took over the facility to ramp up production to make good on its promise to the US government of 100 million doses by the end of May. Only about 9 million of the company’s doses have been delivered to states and are awaiting administration, according to CDC data.
Previously, concern over the blood clots was confined to AstraZeneca’s vaccine, with European regulators saying last week they found a possible link between the shots and an exceedingly rare type of blood clot presenting with low platelets, a situation found more commonly in young people.

Nevertheless, the European Medicines Agency emphasised that the benefits for the vaccine outweigh the risks. Despite this, several countries imposed restrictions on vaccine eligibility and some such as Britain and Greece recommending that people under a certain age be offered alternatives.

Unlike the Pfizer/BioNTech and Moderna vaccines which use mRNA to train the immune system to recognise the SARS-CoV-2 spike protein, the J&J and AstraZeneca vaccines use an adapted adenovirus to introduce the spike protein antigen into the body. Adenoviruses were first identified in the 1950s as a family of similar disease-causing viruses. AstraZeneca’s vaccine uses a chimpanzee adenovirus while the J&J uses a human one.

Source: Medical Xpress

Categories : COVIDTags :

Netherlands and Ireland Suspend AstraZeneca Vaccine Over Blood Clots

On By ModernMedia

In the wake of reports from Norway of blood clots in people shortly after receiving the AstraZeneca vaccine, the Netherlands and Ireland have suspended its use.

The Dutch Health ministry on Sunday said that there was still no evidence of a direct link between the vaccine and possible adverse effects from Norway and Denmark, and there were no reported cases in the Netherlands.

“We can’t allow any doubts about the vaccine,” Dutch health minister Hugo de Jonge said. “We have to make sure everything is right, so it is wise to pause for now.”

Earlier on Sunday Ireland’s deputy chief medical officer, Dr Ronan Glynn, said that deployment of the AstraZeneca vaccine, which makes up 20% of the country’s 570 000 doses given so far, should be “temporarily deferred” with immediate effect as recommended by the country’s National Immunisation Advisory Committee (NIAC). However, he emphasised that there was no proof that blood clots had been caused by the vaccine.

The first blood clots were reported in Austria, and prompted a wave of concern, with Denmark suspending the AstraZeneca vaccine, along with the north of Italy. These latest cases in Norway resulted in three hospitalisations and one death.

The Norwegian Medicines Agency said the four people who had the AstraZeneca injection all had reduced numbers of blood platelets. It added: “People under the age of 50 who have received the AstraZeneca vaccine and feel increasingly unwell more than three days after vaccination, and who notice larger or smaller blue spots in the skin (skin haemorrhages) must consult a doctor or out-of-hours medical service as soon as possible.

“Similar incidents have been reported in other European countries, and the European Medicines Agency (EMA) is considering whether there may be an association with the coronavirus vaccines. So far, no conclusion has been reached.”

Professor Karina Butler, head of NIAC, said it was acting out of an abundance of caution but wanted a better understanding of this unanticipated cluster of “very serious” clotting events in younger people.

There were similarities to other cases reported elsewhere in Europe, she added. It was necessary to know “was there a possibility of a relationship with the vaccine, something which was rare but very serious and could have significant outcomes”, she said to Virgin Media News.

The agency did not yet know whether more blood clots were happening than expected in the population generally. “But they do seem to have clustered together at a level and in younger people – I mean less than 65 – where we wouldn’t necessarily have expected them to happen and thus the question was should we just pause until we get that information, because above all we want to maintain confidence in the vaccine programme so that people can feel that what they are getting is safe, that any serious safety signal is being thoroughly investigated,” she said. 

In a statement, Dr Glynn said: “It has not been concluded that there is any link between the Covid-19 vaccine AstraZeneca and these cases. However, acting on the precautionary principle, and pending receipt of further information, the NIAC has recommended the temporary deferral of the Covid-19 vaccine AstraZeneca vaccination programme in Ireland.”

Source: The Guardian