DURING THIS coronavirus-blighted year, through many difficult days of isolation and fear, the world has hoped for better times. It has hoped for better treatments for covid-19, faster testing and better understanding of how SARS-CoV-2 wreaks havoc on the human body. Many of those things have arrived. But one hope in particular has been uppermost: that a vaccine may be found. Its fulfilment seems to be in sight.

On November 9th Pfizer and BioNTech, two pharmaceutical firms, announced that the vaccine on which they have been collaborating is more than 90% effective in preventing symptomatic cases of covid-19. This is an astonishing result for a first-generation vaccine. Many had not dared to hope for efficacy of anything over 70%.

The news sent Pfizer’s shares leaping by 15% and the much smaller BioNTech’s by 24% when America’s stockmarket opened. The broader belief that a vaccine might return life to something like normal pushed the S&P 500 up by 3.6%, on course for a record high. Shares in airlines and banks climbed; those of Cineworld, a cinema chain, jumped by more than 50%. Europe’s leading markets had already risen by between 5% and 8%.

Richard Hatchett, the head of CEPI, a foundation that funds research into vaccines for pandemics, said the results were “hugely positive and encouraging”. He added that they increase the probability that many of the other vaccines that are being pursued would also be successful.

This matters, because one covid vaccine will not be enough, not least because the Pfizer-BioNTech vaccine, labelled BNT162b2, needs to be kept ultracold, and global distribution will be difficult. It also requires two jabs, three weeks apart. Many governments will be hoping for a vaccine that can be kept at something closer to room temperature, and which requires only a single dose.

The Pfizer-BioNTech vaccine relies on a technology known as messenger RNA, or mRNA. The jab injects genetic material from the virus into the body, which uses this material to create a protein normally seen on the surface of covid virus particles, which in turn stimulates the immune system. It is being tested on an ethnically diverse group of 43,000 people, and the trial is not yet complete.

The results announced so far are based on an interim analysis conducted by an independent data-monitoring group. The firms plan to submit their data for review in a scientific publication. It is possible that the efficacy estimate could change, as further data are gathered. That said, the results are sufficiently remarkable that it is unlikely that the final outcome will be anything other than an extremely useful vaccine.

Three important questions about the vaccine remain. One is the extent to which it works in elderly people, one of the groups most vulnerable to covid-19, and who may not respond as well. The other is whether it prevents infectiousness (it remains possible that a vaccine could prevent someone from getting the symptoms of covid-19, but not from spreading it to others). Third, its long-term efficacy is also entirely unknown.

Even so, there is little doubt that the findings are enormously positive. Moreover, Pfizer says that no serious safety concerns have arisen in the trials under way, although further efficacy data are being collected.

News about two more vaccines, from AstraZeneca, another big pharma company, with a team at Oxford University, and Moderna, an American biotechnology company, is also expected in the coming weeks. The AstraZeneca-Oxford vaccine is already known to stimulate a good immune response in the elderly. Even if Pfizer’s vaccine does not do so well in this group, therefore, there is a good chance that another will do this job.

In short, the arrival of vaccines to tame the pandemic is now within reach. But it will take time. The next step will be for Pfizer to apply for emergency authorisation for the vaccine in America and Europe. The World Health Organisation (WHO) has a process for allowing such authorisations to be used in countries without regulatory agencies.

The application for BNT162b2 will have to wait until the third week of November. Pfizer will not apply until it has gathered two months of safety data from participants in the trial. Agencies might authorise it for use in high-risk groups (eg, hospital doctors and nurses) by the end of the year, pending further safety data; broader approval could come in the first quarter of 2021.

Supplies of vaccines will also be limited at first, even though mass manufacturing of BNT162b2 has been under way since October. Current projections suggest 50m vaccine doses will be available in 2020, and 1.3bn in 2021.

There are also formidable distributional challenges ahead. The world has never undertaken vaccination on such a large scale. UNICEF, the UN’s children’s agency, will be one of the bodies leading the global distribution of covid-19 vaccines.

It says that annually it procures 600m-800m syringes for routine childhood immunisations and that the demands of covid are likely to treble or quadruple this number. Both UNICEF and the WHO are mapping the global availability of cold-chain storage capacity in order to help countries receive vaccines.

In the longer term, vaccine efficacies of 90% will make it feasible to generate herd immunity. If enough people take such an efficacious vaccine, then those who do not or cannot will be protected too. In the short term, though, the priority is for the world to do a good job of targeting vaccine shots to where they are most needed. This will help control the pandemic and ensure a speedier recovery of the world economy. Travel and trade can also return to something approaching normal.

There is one other wrinkle in an efficacy of 90%: it is as close to complete protection as vaccinology can muster. It becomes an essential tool for doctors, nurses and social workers, enabling them to do their jobs with less fear. People in many other professions will feel the same, but they will have to be patient and wait their turn.

There is one other cause for celebrating. The mRNA approach that Pfizer and BioNTech are using has never been shown to work in humans before. The data gathered from the large-scale trials of this “platform” technology mean the firms can quickly and easily make minor revisions to the mRNA sequence, thus changing the proteins the body develops immunity to. This means that if new strains of covid-19 emerge, appropriate revisions of the vaccine could be created rapidly to contain it.

It is likely to be several months after any regulatory approval until vaccines have an impact on the course of the pandemic. But this marks the beginning of the end.