How a year of intense scientific effort unravelled the secrets of a virus that shut down the world.

Some trial volunteers were given shots half the planned strength, so how does that affect the results?

The large-scale trial is both a triumph and a disappointment, after other groups had better results.

Hopes are rising that an effective vaccine against Covid-19 will be available soon.

The results add to growing confidence that vaccination can end the pandemic.

Vaccines may cause wide-scale changes in the immune system which can boost the body's protection.

AstraZeneca describes the pause in its keenly-awaited final clinical trials as routine.

Nigeria is now rid of wild polio having had more than half of global cases less than 10 years ago.

A second Ebola vaccine is to be offered to thousands of people in the Democratic Republic of Congo.

The virus can cause 'immune amnesia' which shifts our defences back to a 'baby-like' state.