By Luke Andrews for MailOnline
The announcement that Pfizer’s Covid-19 vaccine could be up to 90 per cent effective has sparked claims society could go back to normal by spring next year.
But with most data from the trials still unpublished, several scientists have sounded a note of caution over whether the vaccine will work.
Does the vaccine actually prevent infection?
Preliminary results from the trial say that out of the 94 people that have tested positive for the virus no more than eight received the vaccine.
But scant information has been released on how these infections were identified.
If tests were only carried out after someone developed symptoms, it may be that asymptomatic infections were missed – meaning the vaccine does not prevent infection.
On the other hand, if all the trials 43,500 volunteers were tested repeatedly this would reveal the vaccine conferred immunity against the virus.
Additionally, it is unclear what sort of infections the eight that tested positive suffered – and, hence, whether the vaccine curtailed some of the worst impacts.
Professor Eleanor Riley, an immunologist at the University of Edinburgh, said that without further information it remained unclear whether the vaccine reduced symptoms or stopped infection.
How long will immunity last?
This remains tantalisingly unclear, and can only be revealed by continuing to monitor those that have received the jab.
Pfizer launched its trial in July and has so far not recorded any candidates in which immunity relapsed in the first few months, according to reports.
Several vaccines require top-up shots every couple of years, due to waning immunity. The jab against diptheria, polio and tetanus, for example, needs to be given every ten years to ensure immunity.
Will the vaccine help the elderly?
The early release from Pfizer still has not revealed whether the vaccine will help the elderly.
Details on the ages of the 43,500 candidates in the early trial are not known, and neither are the ages of those who tested positive for the virus.
If the virus was only trialled in a middle or young age group however, this could mean that further tests will be required before it can be administered to older members of society.
Professor Tracy Hussell, an immunologist from the University of Manchester, previously warned that as people get older their immune systems become less responsive – meaning a vaccine may not trigger the required response to provide immunity.
Who are the volunteers that tested positive for the virus?
Pfizer is yet to release information on the characteristics of the 94 people that tested positive for the virus, and the at least eight people that got the infection despite receiving the jab.
This is important because it will reveal whether the jab has managed to protect more vulnerable individuals to the virus, or if they are still susceptible to it.
It will also reveal whether there is a significant difference between those that caught the virus without receiving the vaccine and those that did.