Ο European Medicines Agency (EMA) announced that the overall benefits of its vaccines AstraZeneca and the Johnson & Johnson against COVID-19 outweigh the risks, even when they added warning labels to both vaccines for extremely rare but potentially fatal blood clots.
Johnson & Johnson said it will continue deliveries of its vaccine in Europe, in accordance with EMA guidelines, while U.S. officials continue to review eight reported cases in the U.S. of rare thrombosis combined with low platelet count after administration of the vaccine.
At the same time, the UK health regulator has recommended that people under 30 years of age should receive a different coronavirus vaccine, if possible, instead of the AstraZeneca vaccine, while some other European countries only give the vaccine to older people.
Amid concerns that these rare cases of side effects could undermine confidence in the global vaccination campaign against coronavirus pandemic, vaccine and immunology experts state that the risks of thrombosis for both vaccines remain extremely low and vaccines are highly effective in preventing deaths and serious diseases from Covid-19.
Let's look at the analysis of the data, according to Reuters.
What is known so far
Reports of AstraZeneca and J&J vaccines include extremely rare cases of thrombosis, most notably a type of thrombosis called cerebral venous sinus thrombosis (CVST) seen in combination with low platelet levels, called thrombocytopenia.
The European regulator also said that most of the clots occurred in the brain and abdomen, as with AstraZeneca's vaccine Vaxzevria, which is also being studied for similar clotting problems.
A committee of the US Centers for Disease Control and Prevention (CDC) has scheduled a meeting for 23 April to consider the case linking thrombosis to the J&J vaccine, and a decision is likely to be issued. The US agencies, like the European agencies, characterize these vaccine-associated thrombosis cases as extremely rare.
The numbers
According to the European Medicines Agency, 325 cases of rare thrombosis combined with low platelet counts have been recorded worldwide following the administration of Covid-19 vaccines, at a time when over 928 million doses of vaccines have been administered worldwide, according to a New York Times count.
In particular, 287 cases have been recorded involving AstraZeneca's vaccine, 8 with Johnson & Johnson's, 25 with Pfizer's and 5 with Moderna's, said Peter Arlette, head of data analysis at the EMA.
Of this total, 142 cases have been recorded in the European Economic Area (EEA) from nearly 30,000,000 doses of Astrazeneca vaccine administered in the last three months in the UK and the EEA.
The EMA review of J&J's vaccine covered eight cases of people receiving the vaccine in the US. All of the cases were people under 60 years of age and most were women who developed symptoms within three weeks of receiving the vaccine.
These 8 cases occurred while 8,000,000 doses of the J&J vaccine have been administered in the US so far.
The EMA said earlier this month that of the cases it has looked at in depth, 18 have resulted in death.
What do the pharmaceutical companies say?;
J&J said that new labeling on its vaccine packages will include a warning about the risk of the rare side effect and instructions on how to recognize and treat it. The company announced yesterday 20 April that it would restart shipments to the European Union, Norway and Iceland and is working to restart clinical trials.
AstraZeneca, which still distributes its vaccines, said it is «working to understand individual cases and possible mechanisms that could explain these extremely rare events».
What do the regulators say?;
The US regulator has suspended the use of J&J's monostasis vaccine «as a maximum precautionary measure» to ensure that healthcare providers are fully aware of potential side effects and can plan for «appropriate recognition and management».
In part, the moratorium served to ensure that doctors know the treatment options, including which drugs to administer to help treat thromboses, without further endangering patients' lives.
The UK's medicines and healthcare products regulator, meanwhile, has issued its recommendation for the use of an alternative vaccine to AstraZeneca's in people under 30 years of age after reviewing 79 cases of rare thrombosis associated with low platelet counts, with 19 deaths - 13 women and six men.
Eleven of the deaths involved people under 50 and three under 30.
What treatment is recommended?;
In the US, health officials have reported that the treatment of thromboses possibly related to the J&J vaccine differs from what may be considered standard in such cases.
«Usually, an anticoagulant drug called heparin is used to treat thromboses,» they point out. «In this context, administering heparin can be dangerous and alternative treatments should be given,» they add.
The EMA, so far, has stated that heparin should not be given until a diagnosis of a similar condition - called heparin-induced thrombocytopenia (HIT) - has been ruled out. Alternative anticoagulants such as fondaparinux or argatroban can be used.
But even when HIT is ruled out, the EMA notes that «it is not yet clear whether patients who develop thrombosis syndrome after vaccination could be treated with heparin, mainly because there is little evidence.».
German doctors and scientists investigating the AstraZeneca vaccine-related thromboses have also said that the issue of heparin remains «unclear» and have recommended that medical professionals administer intravenous immunoglobulin along with an anticoagulant.
How did the health regulators come to their decisions?;
For AstraZeneca's vaccine, as reported by the Athens and Macedonian News Agency, the EMA said in March that, on average, only 1.35 cases of CVST could normally be expected in age groups under 50 within 14 days of receiving the vaccine.
In comparison, four out of 10,000 women would experience thrombosis after taking birth control pills.
British officials who recommended that people under the age of 30 receive an alternative vaccine obtained statistics from the Wheaton Centre at Cambridge University.
According to the Centre, the risk of serious harm from vaccination decreases as the age of vaccinees increases, and the number of intensive care unit admissions decreases rapidly thanks to vaccinations, reinforcing the benefit/risk ratio of AstraZeneca's vaccine.
The Centre concluded that just 0.4 people for every 100,000 in the 50-59 age group will suffer vaccine-related harm, while 95.6 ICU admissions per 100,000 people will be avoided.
What is the EU doing now?;
The EMA, which states that the benefits of using AstraZeneca and J&J vaccines continue to outweigh the risks, has said that unusual clots with low platelet counts should be reported as very rare side effects and has left countries to decide how to proceed.
Their decisions may vary from country to country, the EMA said, depending on factors such as infection rates and whether vaccine alternatives are available. Denmark, for example, chose to suspend the use of AstraZeneca's vaccine and is still considering plans for J&J's vaccine.
Is there a theory about the cause of thrombosis?;
Among the possible causes being investigated is that the vaccine activates an unusual antibody in rare cases. So far, risk factors such as age or gender have not been separated.
While most of the cases reported so far involving the AstraZeneca vaccine have been in women, scientists in Germany say this may be misleading, as women make up the largest population group of people who have received the vaccine.
Health regulators and scientists are also investigating whether the thrombosis problem could affect the entire class of so-called viral vector-based vaccines, which the EMA said is possible, noting differences in the two vaccines.
German scientists at the University of Greifswald have concluded that the extremely rare cases of low platelet thrombosis - something they call «VITT (i.e. immunologically induced thrombotic thrombocytopenia after vaccination) - are triggered in part by antibodies found in affected patients after vaccination with the AstraZeneca vaccine.
Separately, Norwegian scientists came to similar conclusions in their own research.
J&J has agreed to work with scientists at Griffithswald University to investigate the possible causes.
