Denmark suspending use of the AstraZeneca COVID-19 jab is another dark cloud over a troubled vaccine

• Denmark and Norway suspended use of AstraZeneca's coronavirus vaccine on Thursday.
• This is another in a series of troubles for the jab, which was already dogged by problems.
• Poorly-communicated trial results and widespread hesitancy in Europe set the vaccine back.

Today, Denmark said it was suspending its use of the Oxford/AstraZeneca vaccine while it was investigating several cases of blood clots among people who had received the jab. Norway followed a few hours later.

Let's be clear. To date, all signs point towards AstraZeneca's vaccine working and being safe. Multiple respected regulators cleared it for us, and millions of people have had the shot.

Countries have to investigate serious adverse events when rolling out vaccinates. This is not uncommon, and does not mean that the vaccine has caused the adverse event. Denmark has said the clots could be a coincidence.

Nonetheless, the suspensions sent shockwaves around the world. It is the latest in a series of problems for the jab, which have eroded people's trust and led to hesitancy.

Almost from the beginning, the AstraZeneca vaccine faced difficult questions over its clinical trials.

When the results came, they too caused confusion by giving two very different figures for how effective the vaccine was. It later became clear that a mistake led to half of their trial participants not receiving a full dose of the vaccine.

The vaccine efficacy it reported in its clinical trials is also lower than other vaccines. This has led to some patients in Europe and the UK, which are relying on the jab for a big part of their vaccine rollouts, to turn it down, thinking that it was not as effective.

Experts argued that the efficacy figures are not directly comparable - and that the imperative of getting out as many vaccine as possible outweighs the relatively small differences in trial results.

Another setback came as several European countries decided that they would not give the jab to those at most risk of COVID-19, those over 65.

They pointed to there not being a lot of data available in clinical trials for those over the age of 65, though some nations have started to reverse those decisions.

Data from the real-world rollouts was a boost, suggesting that the AstraZeneca jab was doing its job - stopping people from dying with COVID-19 - just as well as the other jabs.

European nations, such as France and Germany, have since then been pushing to rebuild trust in the vaccine, but faced a difficult path.

As officials in Denmark have said, the suspension is a precaution. It may turn out that the vaccine was fine all along. But shaken confidence is hard to restore, and AstraZeneca's already-difficult path is now a bit harder.