Oxford/AstraZeneca COVID-19 vaccine may be around 85 to 90 per cent effective against symptomatic disease, Public Health England (PHE) said on Thursday, while cautioning that it did not yet have enough data to be conclusive.Britain has suffered one of the worst death tolls globally from the pandemic, but has also had one of the fastest vaccine rollouts, generating a lot of data about the use of the shots in real-world settings.It was the first country to roll out AstraZeneca’s vaccine, which faced questions over the construction of its clinical trials, the efficacy of the vaccine and the optimal gap between doses of its shot.