As cases of coronavirus increase around the globe, the focus is turning to finding a vaccine.
We've answered some of the big questions about vaccines and how soon one for coronavirus could be ready.
How does a vaccine work?
Vaccines are like teachers - their pupil is the immune system and their lesson is how to fight infection.
Vaccines harmlessly show viruses or bacteria (or even small parts of them) to the immune system. The body's defences recognise it as an invader and then learn how to fight it.
Then if the body is ever exposed for real then it already knows how to fight the infection.
What different types are there?
The main method of vaccination for decades has been to use the original virus.
So the measles, mumps and rubella vaccine is made by using weakened versions of those viruses that cannot cause a full-blown infection. The seasonal flu jab is made by taking the main strains of flu doing the rounds and completely disabling them.
The work on a new coronavirus vaccine is using newer, and less tested, approaches called "plug and play" vaccines. Because we know the genetic code of the new coronavirus, Sars-CoV-2, we now have the complete blueprint for building that virus.
Some vaccine scientists are lifting small sections of the coronavirus's genetic code and putting it into other, completely harmless, viruses.
Now you can "infect" someone with the harmless bug and in theory give some immunity to the coronavirus.
Other groups are using pieces of raw genetic code (either DNA or RNA depending on the approach) which once injected into the body should start producing bits of viral proteins which the immune system again can learn to fight.
What's the progress so far on finding one for coronavirus?
Researchers have developed vaccines and are starting to test them on animals.
If one is found, how quickly could it be made available?
Realistically it is going to be mid-way through next year at best.
So there are vaccines being tested in animals, if that goes well there could be human trials later in the year. But even if scientists can celebrate having developed a vaccine before Christmas there is still the massive job of being able to mass-produce it.
All of this is happening on a unprecedented timescale and using new approaches to vaccines so there are no guarantees everything will go smoothly.
Remember there are four coronaviruses that already circulate in human beings. They cause the common cold and we don't have vaccines for any of them.
Would it protect people of all ages?
It will, almost inevitably, be less successful in older people. This is not due to the vaccine itself, but aged immune systems do not respond as well to immunisation. We see this every year with the flu jab.
Could there be any side effects?
All medicines, even paracetamol, have side-effects. But without clinical trials it is impossible to know what the side-effects of an experimental vaccine may be.
Until a vaccine is developed, what treatments are available?
Vaccines prevent infections and the best way of doing that at the moment is good hygiene.
If you are infected, then for most people it would be mild. There are some anti-viral drugs being used in clinical trials, but we cannot say for sure any of these work.