Several countries halt AstraZeneca jab: Does the vaccine cause blood clots?

More than 70 countries have authorised the Oxford- AstraZeneca vaccine and 350 million doses have been doled out across the world. Seventeen million people have been vaccinated in the European Union and UK.

But several countries, starting with Denmark last week, have temporarily halted the use of the AstraZeneca vaccine in recent days to investigate cases of blood clots that occurred after vaccination. They include Italy, Germany, France, Ireland, Thailand, the Netherlands, Norway, Iceland, Congo and Bulgaria.

The number of blood clot cases in vaccinated people is no higher than that seen in the general population.

Blood clots can travel through the body and cause heart attacks, strokes and deadly blockages in the lungs. There are primarily two types of blood clots that are being reported.

The first is deep vein thrombosis (DVT), a condition when blood clots form in a vein located deep inside your body. It usually occurs in the thigh or lower leg. It is most commonly seen in people above 50 years of age and can enhance the chances of developing a pulmonary embolism.

The second type is pulmonary embolism is much more severe. It is a blockage in one of the pulmonary arteries in your lungs. It restricts blood flow and decreases oxygen levels and in most cases, it proves to be fatal.

So far across the EU and UK, there have been 15 events of deep vein thrombosis (DVT) or thrombocytopenia and 22 events of pulmonary embolism reported among those given the vaccine.

According to the European Medicines Agency, there is currently no indication that vaccination had caused these conditions. There’s not much information on the existence of co-morbidities in these patients either. But a few adverse reactions have raised questions and concerns.

Meanwhile, the World Health Organization appealed to countries not to pause vaccination campaigns after a few European nations and one in Asia joined handfuls that have suspended the use of AstraZeneca's Covid-19 vaccine over safety fears.

The WHO said its advisory panel was reviewing reports related to the shot and would release its findings as soon as possible. But it said it was unlikely to change its recommendations, issued last month, for widespread use, including in countries where the South African variant of the virus may reduce its efficacy.

"It's very important to understand that, yes, we should continue using the AstraZeneca vaccine. All that we're looking at is what we always look at: any safety signal must be investigated. In fact, it is very important that we are hearing safety signals because if we were not hearing about any safety signals, then that would suggest there is not enough review and vigilance. We must always ensure we look for any safety signals when we roll out vaccines and we must review them. But there is no indication to not use it,” WHO spokeswoman Margaret Harris said.

But even after this statement, not everybody is convinced.

At least 16 countries have placed a temporary suspension on the vaccine and more countries may follow suit.

AstraZeneca's shot was among the first and cheapest to be developed and launched at volume since the coronavirus was first identified in central China at the end of 2019 and is set to be the mainstay of vaccination programmes in much of the developing world. The virus has killed more than 2.7 million people.

(With inputs from agencies)