However, they caution that as the study continues the final vaccine efficacy percentage may vary.
Dr Albert Bourla, Pfizer chairman and chief executive, said: “Today is a great day for science and humanity.
“The first set of results from our Phase 3 Covid-19 vaccine trial provides the initial evidence of our vaccine’s ability to prevent Covid-19.”
He added: “We will continue to collect further data as the trial continues to enrol for a final analysis planned when a total of 164 confirmed Covid-19 cases have accrued.
Who will get the vaccine first?
The government’s Joint Committee on Vaccination and Immunisation have set out guidance on which groups will be prioritised if a successful vaccine materialised.
The guidance published on September 25 is provisional on preliminary information on the vaccines in development, and provisional timelines for vaccine availability, and is subject to change.
The committee strongly agree that a simple age-based programme will likely result in faster delivery and better uptake in those at the highest risk.
Whether health and social care workers should be prioritised above, alongside, or below, persons at highest risk from COVID-19 would depend on the characteristics of the vaccines when they become available and the epidemiology of disease at the time of delivery.
The priority groups are set out to be the following:
- older adults’ resident in a care home and care home workers
- all those 80 years of age and over and health and social care workers
- all those 75 years of age and over
- all those 70 years of age and over
- all those 65 years of age and over
- high-risk adults under 65 years of age
- moderate-risk adults under 65 years of age
- all those 60 years of age and over
- all those 55 years of age and over
- all those 50 years of age and over
- rest of the population (priority to be determined)
The prioritisation could change substantially if the first available vaccines were not considered suitable for, or effective in, older adults.
Other vaccine trials are underway…
The latest data in the Oxford University trials shows that their vaccine produces a “strong” immune response among the elderly. Analysis of the Phase II stage of the trial process reportedly found similar responses across all age groups, in findings that have been hailed as a “milestone” in the fight against the pandemic.
As well as several Phase 3 trials taking place on vaccine candidates around the world, the UK is starting some “human challenge trials”, where volunteers are exposed to the virus as part of testing the vaccines.
The Imperial human challenge trial is being run by hVivo, a spin-off company from Queen Mary University of London. Already roughly 2,000 people have signed up to take part in challenge studies in Britain through the group 1Day Sooner.
Those testing the vaccine will be given the jab and will then wait a month for antibodies to build. The volunteers will then be exposed to the virus.
Currently, vaccines are tested at population level, so scientists look to see whether a smaller percentage of people are infected than would be expected in the vaccine arm of the trial compared to a control group.
However worldwide lockdowns have meant that virus in the community has been very low in recent months, and scientists have struggled to get enough data to know whether their vaccines are working.
Oxford University has been forced to move some of its vaccine testing to South America and South Africa, although it is expecting results back soon.
What’s the latest on Oxford?
Oxford’s vaccine trial was halted on September 8 after a participant in the UK had an adverse reaction.
The vaccine, developed with AstraZeneca, cleared phases one and two human trials and progressed to the third phase where it was being tested on a larger number of participants.
But the adverse reaction experienced by the participant in the vaccine trial may not have been caused by the experimental vaccine itself, it has since been claimed. One participant died during trials in Brazil, but trials have continued as the death is understood not to be linked to the trial.
Oxford announced on September 12 that clinical trials of its coronavirus vaccine will resume in the UK. And on October 23, it was announced that human trials of the Oxford and AstraZeneca coronavirus vaccine have also resumed in the US.
Before that, testing had been positive. The full results of the Oxford trials, published on July 20, showed that initial trials on 1,077 British adults found that the vaccine induced strong antibody and T-cell responses, which may improve further after a booster jab.
The discovery is promising because separate studies have suggested that antibodies may fade away within months while T-cells can stay in circulation for years.