This is a good summary by Prof Paul Hunter, Professor in Medicine, The Norwich School of Medicine, University of East Anglia:
“The publication of the results of the phase 3 trial of the Pfizer/BioNTech COVID vaccine have now been published. This follows the publication of the results of the Oxford AstraZeneca vaccine by just a few days and it is very tempting to compare the two. As has been widely reported the Pfizer/BioNTech vaccine is an mRNA vaccine whilst the Oxford AstraZeneca is an adenoviral vector vaccine.
“The Pfizer/BioNTech included data on 43,448 participants compared to 8,895 in the Oxford AstraZeneca standard dose regimen and 2741 in the Oxford AstraZeneca low dose regimen.
“As far as I can tell both trials had similar primary outcome measures so they were measuring the same thing.
“The estimated vaccine efficacy for Pfizer from 7 days after the second injection was 95.0% (Confidence Intervals 90.3 to 97.6%). By contrast the efficacy for the Oxford standard dose regimen was 62·1% (41·0 to 75·7%) and for the low dose regiment was 90·0% (67·4 to 97·0%). Reflecting the smaller number of participants in the two Oxford dose trials, its efficacy estimates are much less precise and so more uncertain than the Pfizer study. The Pfizer study presented estimates of the effectiveness in older people and found efficacy >90% in >55, > 65 and >75 year olds, though confidence intervals were wider in the older age groups. The efficacy of the Oxford vaccine in people over 55 years could not be assessed and the low dose vaccine was not given to people over 55 so there is no data on that dose regimen. The Pfizer study reports good efficacy in Black and Hispanic participants. The Oxford study has not yet reported on efficacy in BAME populations. Neither study had sufficient numbers of cases of severe COVID or fatalities to make precise estimates of efficacy at preventing severe disease. Of ten cases of severe COVID in the Pfizer study 9 were in the placebo group and 1 in the vaccine group. In the Oxford study there was just 1 severe case and ten hospitalised cases and they were in the placebo group. The Pfizer study did not report studies of the impact of its vaccine on asymptomatic infection. The Oxford study reported that efficacy for “asymptomatic or symptoms unknown infection” based on weekly self-swabbing was 3·8% (−72·4 to 46·3%) following standard dose and 58·9% (95% CI 1·0 to 82·9) following low dose regimen.
“As to safety The Pfizer trial reported serious adverse reactions in 0.6% of vaccine recipients and 0.5% of placebo recipients. In the Oxford study serious adverse events were reported in 168 participants, 79 of whom were in the vaccine group (1.4%) and 89 were in the control group (1.5%), many of whom received a meningococcal vaccine. It would appear that the Pfizer vaccine study reported a lower risk of serious adverse events than the Oxford study but in both studies the probability of severe side effects was not that different between the vaccine and control arms. But many of the Oxford control subjects received a meningococcal vaccine which itself may cause serious adverse events so this needs to be interpreted carefully.
“So in conclusion the results do suggest that both vaccines are effective and safe. However, the Pfizer vaccine has rather greater reported efficacy than the Oxford standard dose vaccine and possibly fewer serious adverse reactions. The Pfizer study also has evidence showing high efficacy in older age groups and in Black and Hispanic but not yet Asian individuals. The Oxford study does not yet enable efficacy in these at risk groups to be determined. As yet there is no phase 3 data on the low dose Oxford vaccine in people over 55 years old, the main target group for immunization against COVID”.
via: www.sciencemediacentre.org/expert-reaction-to-phase-3-results-for-the-pfizer-biontech-bnt162b2-mrna-covid-19-vaccine/
That said, don't get hung up on efficacy percentages and other details - the best decision you can make is to take whatever vaccine you are offered, they all offer good protection against the variant that is dominant in the UK.
The variant originally identified in South Africa as well as the UK voc with the same mutation are not going to be dominant here "in the next 4 weeks", that's just not mathematically possible.
And we are not Cyprus - offering people a menu of vaccine choices would be a logistical nightmare, would massively complicate and slow down our very impressive rollout and would cost lives.