Coronavirus is spreading worldwide, but there are still no vaccines to protect the body against the disease it causes, Covid-19. Report presents article published by Health and science correspondent of BBC James Gallagher.
Medical researchers are working hard to change that.
Why is a coronavirus vaccine important?
The virus spreads quickly, and the majority of the world's population is still vulnerable to it. A vaccine would provide some protection by training people's immune systems to fight the virus so they should not become sick.
This would allow lockdowns to be lifted more safely, and social distancing to be relaxed.
What sort of progress is being made?
Research is happening at breakneck speed. About 200 groups around the world are working on vaccines, and 18 are now being tested on people in clinical trials.
The first human trial data appears positive, showing the first eight patients all produced antibodies that could neutralize the virus.
However, no-one knows how effective any of these vaccines will be.
When will we have a coronavirus vaccine?
A vaccine would generally take years, if not decades, to develop. Researchers hope to achieve the same amount of work in only a few months.
Most experts think a vaccine is likely to become widely available by mid-2021, about 12-18 months after the new virus, known officially as Sars-CoV-2, first emerged.
That would be a substantial scientific feat, and there are no guarantees it will work.
Four coronaviruses already circulate in human beings. They cause common cold symptoms, and we don't have vaccines for any of them.
What still needs to be done?
Multiple research groups have designed potential vaccines. However, there is much more work to do.
Trials need to show the vaccine is safe. It would not be useful if it caused more problems than the disease
Clinical trials will also need to show that the vaccine provokes an immune response that would protect people from getting sick
A way of producing the vaccine on a vast scale must be developed for the billions of potential doses
Medicines regulators must approve it before it can be given
Finally, there will be a huge logistical challenge of actually immunizing most of the world's population
The success of lockdowns has made the process slower. To know if the vaccine works, you need people to be infected.
Giving people the vaccine and then deliberately infecting them (known as a challenge study) would give quicker answers, but is currently seen as too dangerous and unethical.
How many people need to be vaccinated?
It is hard to know without knowing how effective the vaccine is going to be.
It is thought that 60-70% of people needed to be immune to the virus to stop it from spreading quickly (known as herd immunity).
But that would be billions of people around the world even if the vaccine worked perfectly.
How do you create a vaccine?
Vaccines harmlessly show viruses or bacteria (or even small parts of them) to the immune system. The body's defenses recognize them as an invader and learn how to fight them.
Then if the body is ever exposed for real, it already knows what to do.
The main method of vaccination for decades has been to use the original virus.
The measles, mumps, and rubella (MMR) vaccines are made by using weakened viruses that cannot cause a full-blown infection. The seasonal flu jab takes the main strains of flu doing the rounds and completely disables them.
Some scientists, particularly those in China, are using this approach.
There is also work on coronavirus vaccines 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 have the complete blueprint for building it.
Researchers in Oxford have put small sections of its genetic code into a harmless virus that infects chimpanzees. They hope they have developed a safe virus that looks enough like the coronavirus to produce an immune response.
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 in which the immune system can learn to fight. However, this approach is completely new.
Would a vaccine protect people of all ages?
It will, almost inevitably, be less successful in older people, because aged immune systems do not respond as well to immunization. We see this with the annual flu jab.
It may be possible to overcome this by either giving multiple doses or giving it alongside a chemical (called an adjuvant) that gives the immune system a boost.
Who would get a vaccine?
If a vaccine is developed, then there will be a limited supply, initially, so it will be essential to prioritize.
Healthcare workers who come into contact with Covid-19 patients would top the list. The disease is most deadly in older people, so they would be a priority if it were effective in this age group.
The UK has also said other people considered to be at high risk - potentially included those with some conditions or from certain ethnicities - may be prioritized.