According to this BBC News article, it's 4 per 1M: https://www.bbc.com/news/health-55302595 https://www.bbc.com/news/health-55302595 Quote: "The MHRA said ab

According to this BBC News article, it's 4 per 1M: https://www.bbc.com/news/health-55302595 https://www.bbc.com/news/health-55302595 Quote: "The MHRA said about four people in a million would normally be expected to develop this particular kind of blood clot - though the fact they are so rare makes the usual rate hard to estimate."