Approval of a coronavirus vaccine seems within reach. However, there are a number of questions that have not yet been answered.
Effectiveness
Pharmaceutical companies Pfizer and BioNTech say their experimental vaccine is 90% effective in preventing Covid-19. This is only a preliminary assessment, however. Data about effectiveness within certain demographic groups is not yet available.
Leif Erik Sander of Berlin's Charite hospital says the level of effectiveness for people in high-risk groups has not yet been ascertained.
The claim of 90% effectiveness has yet to be published in a medical journal, Sander says, adding that if it is proven, it would be unusually high.
Access
The European Commission has held months of negotiations with Pfizer and BioNTech so that the vaccine can reach member states as soon as possible once it is approved.
German Health Minister Jens Spahn says Berlin has requested some 100 million doses of the vaccine. The 27 European Union members will receive a share of doses that corresponds to their population.
Distribution
Who will get a dose of the vaccine first? According to a position paper from a roster of experts, elderly people, those with co-morbidities and health care workers will be prioritized when it comes to administering the vaccine.
People working in jobs that are crucial for the functioning of society - including government workers, police officers, firefighters and teachers - will also be prioritized.
There will be more concrete guidelines from the government in the coming weeks.
Practical implementation
Vaccines will be administered in vaccination centres. The transport and storage of the vaccine could prove challenging considering the fact that it has to be kept at temperatures of 70 degrees Celsius below freezing.
Pfizer said in a statement in September that the vaccine could be kept for a period of five days at regular refrigerator temperature (between 1 and 8 degrees Celsius).
Lasting immunity?
It is improbable that one dose of the coronavirus vaccine will make the recipient immune for a lifetime. Experts say that it will have to be renewed regularly, similar to the annual flu vaccine.
A major unanswered question is whether someone who has been immunized can still transfer the virus to other people. This would present a major problem in the case of health care workers.
