Last checked at 
By Ludwig Burger and Matthias Blamont
FRANKFURT/PARIS, March 17 (Reuters) - Europe's drug watchdog
is reviewing a small number of reports of bleeding, blood clots
and low platelet counts in people who have received
AstraZeneca's coronavirus vaccine.
The European Medicines Agency (EMA) has said it has so far
found no causal link between the vaccine and the incidents. The
World Health Organization has also said there was no proven link
and people should not panic.
At least 13 EU member states including Germany, France,
Italy have suspended use of the shot pending the outcome of
EMA's probe.
Here's what we know so far:
WHAT HAS HAPPENED?
More than 45 million COVID shots by all manufacturers have
been administered across the EU and the European Economic Area
since vaccinations started almost three months ago.
The EMA is investigating reports of 30 cases of unusual
blood disorders out of 5 million people who got the AstraZeneca
vaccine in the EU.
The EMA's focus and primary concern is on cases of blood
clots in the head, a rare condition that's difficult to treat
called cerebral venous thrombosis (CVT).
In Germany, seven people aged 20 to 50 have been diagnosed
with CVT up to 16 days after vaccination as per Monday,
according to the national vaccine authority Paul Ehrlich
Institute (PEI). Based on the known rate of CVT in the general
population, the PEI would have expected one case in 1.6 million.
WHAT HAVE OTHER COUNTRIES AND ASTRAZENECA SAID?
Britain has administered more than 11 million doses of the
AstraZeneca vaccine and reports of blood clots were no greater
than would have occurred naturally. The UK's medicine regulator
has urged Britons to keep on getting their vaccines, including
the AstraZeneca shot.
Canada has said health experts are sure all COVID-19
vaccines being administered in the country are safe, including
AstraZeneca's.
AstraZeneca said on Sunday a review of safety data of more
than 17 million people vaccinated in the United Kingdom and
European Union with its vaccine had shown no evidence of an
increased risk of blood clots.
?
WHAT IS THE EMA INVESTIGATING?
EMA investigators are checking if the frequency of
incidences is higher in the vaccinated population than normal
background rates.
The normal frequency is drawn from public health statistics
or insurance records. This would be combined with a medical
analysis of each case and insight from scientific literature.
EMA's head of safety monitoring, Peter Arlett, added the
rarity of CVT meant the watchdog would have to rely more heavily
on case-by-case analysis rather than on the sparse statistical
data.
A spokeswomen for Germany's vaccine authority, which is part
of the investigation, said EMA would not rule on causality.
Instead, EMA will assess the likelihood of an increased risk
of the condition and weigh that against the benefits of fighting
COVID-19 and providing relief for health systems.
For example, the vaccines developed by Pfizer and
Moderna have been linked with increased risk of
anaphylaxis, but they are still recommended because benefits
outweigh the risks of the side effect, which can be treated.
The regulator has said it remains for now "firmly convinced"
that the product's benefit outweighs any risks.
WHAT DID THE CLINICAL TRIALS SHOW?
AstraZeneca and European regulators have said that concerns
about blood coagulation disorders did not emerge during human
trials.
Safety monitoring after approval is key because extremely
rare side-effects, or those affecting only a small subset of the
population, are near impossible to identify during clinical
trials, according to PEI.
ARE THERE PRECEDENTS OF VACCINE SAFETY SCARES?
In Japan, a governmental recommendation for use of human
papillomavirus (HPV) vaccine to prevent cervical cancer has been
suspended since June 2013, due to media reports of an alleged
pain syndrome. This has drawn criticism from the WHO.
A study published in The Lancet Public Health last year
concluded a continued suspension would lead to thousands of
cancer deaths over the next decades.
In Ukraine https://www.reuters.com/article/us-health-measles-ukraine-insight-idUKKBN1XE15T,
deep mistrust of vaccines has allowed measles to grow into an
epidemic. Vaccine hesitancy there is rooted in corruption and
mistrust of authority but also in a temporary government
suspension in 2008, when a 17-year-old boy died shortly after
receiving a measles-rubella vaccine.
(Reporting by Ludwig Burger and Matthias Blamont
Additional reporting by Kate Kelland in London and Julie
Steenhuysen in Chicago
Editing by Josephine Mason and Nick Macfie)
