There were already some positive preliminary results from the five vaccines being tested in Brazil, so "don't work at all" was already ruled out, I think. Obvio

There were already some positive preliminary results from the five vaccines being tested in Brazil, so "don't work at all" was already ruled out, I think. Obviously the press release from Pfizer isn't going to mention the other vaccines, but a diligent journalist might look up the details and do some kind of comparison. Perhaps the diligent journalists need a bit more time to write their articles. Perhaps we should wait a day or two and consult a better source than the BBC.