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I am a bit concerned about Andrew Pollard's rather brief dismissal of a possible link between the vaccine trials and the SA and Brazil variants. The question doesn't take into account the other sites of the trials - the UK and the USA - where worrying mutations have also arisen - 4 sites strikes one as more than a coincidence. And also the timing of the trials and the emergence of the mutations seems to fit rather.
To say that not enough people were in the trials to have an effect is surely a bit misleading - it would only take one to act as "ground zero". I believe this needs much more investigation. If there is a link, it would show that transmission is not stopped by vaccination and long term would perhaps indicate that the vaccinated may be at an ever increasing risk.