A vaccine to protect against Covid-19 would seem near at hand. One among the nine in the final stages of testing, being developed by America’s Pfizer and Germany’s BioNTech, has created a stir, showing in reported interim results an efficacy rate of “above 90 per cent”. This is encouraging for people eager to end the restrictions that have battered economies and put lives on hold. But it is not yet time for celebration. There can be no guarantees as research is still being carried out, there are logistical challenges, and, for most of us, face masks and social distancing will remain the best way to ward off the disease for some time yet. The results are partial, final, phase 3, tests are still under way and the analysis has yet to be peer reviewed. Much has yet to be learned, including how long those immunised will be protected, whether the vaccine is effective for all age groups and if it prevents infection. Efficacy also is not the same as effectiveness, the former referring to clinical trials carried out under ideal and controlled conditions and the latter relating to performance under real-world circumstances over a long period of time. Still, any glimmer of hope is cause for encouragement after 10 months of restrictions. The announcement came as parts of Asia, Europe and the United States were hit by fresh waves of the coronavirus, prompting a return of curfews and lockdowns. It is therefore good that the Pfizer-BioNTech vaccine is a multinational effort that governments and citizens can trust. The Chinese firm Fosun Pharmaceutical has an agreement to commercialise the drug across the nation. Assuming the vaccine passes all hurdles, a major challenge lies ahead in producing the billions of doses needed and distributing it quickly to the most vulnerable. The vaccine has particular drawbacks. Each person to be immunised will require two doses and Pfizer predicts it can only produce 1.3 billion by the end of next year. Why the Pfizer-BioNTech vaccine is no cure for all coronavirus ills It also needs special handling, requiring specialist ultra-low temperature freezers that keep the drug at minus-80 degrees Celsius (minus 112 Fahrenheit), a challenge for storage and transport. Fortunately, several of the other vaccines in the final stage of testing have been produced using the same method and it is to be hoped that there will be multiple successful drugs able to cope with all circumstances. The urgency to develop a Covid-19 vaccine means that usual procedures and approvals are being fast-tracked. There can be last-minute hitches, as one Chinese firm has found in trials taking place in Brazil. Clinical success is also far removed from the realisation of a safe and effective immunisation programme in all parts of the world. But we would now seem a step closer and if all goes well, with global cooperation, we can sooner rather than later end this crisis.