Danish health authorities said Thursday they were temporarily suspending the use of AstraZeneca's Covid-19 vaccine after some patients developed blood clots since receiving the jab.
The move comes "following reports of serious cases of blood clots among people vaccinated with AstraZeneca's Covid-19 vaccine", the Danish Health Authority said in a statement.
But it cautiously added that "it has not been determined, at the time being, that there is a link between the vaccine and the blood clots".
Austria announced on Monday that it had suspended the use of a batch of AstraZeneca vaccines after a 49-year-old nurse died of "severe blood coagulation problems" days after receiving an anti-Covid shot.
Four other European countries -- Estonia, Latvia, Lithuania and Luxemburg -- have also suspended the use of vaccines from this batch, which was sent to 17 European countries and consisting of one million jabs.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
Denmark has however suspended the use of all of its AstraZeneca supply.
On Wednesday, Europe's medicines watchdog EMA said a preliminary probe showed that the batch of AstraZeneca vaccines used in Austria was likely not to blame for the nurse's death.
As of March 9, 22 cases of blood clots had been reported among more than three million people vaccinated in the European Economic Area, the EMA said.
"It is important to point out that we have not terminated the use of the AstraZeneca vaccine, we are just pausing its use," Danish Health Authority director Soren Brostrom said in the statement.
Denmark said one person had died after receiving the vaccine. The EMA has launched an investigation into that death.
"There is broad documentation proving that the vaccine is both safe and efficient. But both we and the Danish Medicines Agency must act on information about possible serious side effects, both in Denmark and in other European countries," Brostrom said.
The suspension, which will be reviewed after two weeks, is expected to slow down Denmark's vaccination campaign.
Copenhagen now expects to have its entire adult population vaccinated by mid-August instead of early July, the health authority said.Follow our full coverage of the coronavirus pandemic here.