A preliminary analysis shows that the first effective coronavirus vaccine can prevent more than 90% of people from getting Covid-19.
The developers – Pfizer and BioNTech – described it as a “great day for science and humanity”.
The vaccine has been tested on 43,500 people in six countries and no safety concerns have been raised.
The companies plan to apply for emergency approval to use the vaccine by the end of the month.
No vaccine has gone from the drawing board to being proven highly effective in such a short period of time.
There are still huge challenges ahead, but the announcement has been warmly welcomed by scientists with some suggesting life could be back to normal by spring.
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A vaccine – alongside better treatments – is seen as the best way of getting out of the restrictions that have been imposed on all our lives.
The data shows that two doses, three weeks apart, are needed. The trials – in US, Germany, Brazil, Argentina, South Africa and Turkey – show 90% protection is achieved seven days after the second dose.
However, the data presented is not the final analysis as it is based on only the first 94 volunteers to develop Covid-19 so the precise effectiveness of the vaccine may change when the full results are analyzed.
Pfizer chairman Dr. Albert Bourla said: “We are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis.”
Prof. Ugur Sahin, one of the founders of BioNTech, described the results as a “milestone”.
A limited number of people may get the vaccine this year.
The two companies say they will have enough safety data by the third week of November to take their vaccine to regulators.
Until it has been approved it will not be possible for countries to begin their vaccination campaigns.
Pfizer and BioNTech say they will be able to supply 50 million doses by the end of this year and around 1.3 billion by the end of 2021. Each person needs two doses.
Not everyone will get the vaccine straight away and countries are each deciding who should be prioritized.
Hospital staff and care home workers will be near the top of every list because of the vulnerable people they work with, as will the elderly who are most at risk of severe disease.
People under 50 and with no medical problems are likely to be last in the queue.
There are still many unanswered questions as this is only interim data.
We do not know if the vaccine stops you spreading the virus or just from developing symptoms. Or if it works equally well in high-risk elderly people.
The biggest question – how long does immunity last – will take months or potentially years to answer.
There are also massive manufacturing and logistical challenges in immunizing huge numbers of people, as the vaccine has to be kept in ultra-cold storage at below minus 80C.
The vaccine appears safe from the large trials so far but nothing, including paracetamol, is 100% safe.
There are around a dozen vaccines in the final stages of testing – known as a phase 3 trial – but this is the first to show any results.
It uses a completely experimental approach – that involves injecting part of the virus’s genetic code – in order to train the immune system.
Previous trials have shown the vaccine trains the body to make both antibodies – and another part of the immune system called T-cells to fight the coronavirus.
