Though rates of increasing the risk of blood clots for different birth controls vary, the ones that do range from 2-6x. The FDA estimates that in US out of every 10 thousand women using combination oral contraceptives or birth control pills 3 to 9 will develop blood clots each year while for comparison the same rate for women who are not pregnant and do not take COCs is 1 to 5 which is interesting considering the age range of the six cases.

https://www.fda.gov/drugs/drug-safety-and-availability/fda-d...

That said research is beginning to understand the mechanism of these rare blood clots in connection to adenovirus vector meds and since it is so rare it's hard to get a precise number but other studies predict an excess increase of severe blood clots in the range of 1 in every 500 thousand to million patients.

https://www.sciencedirect.com/science/article/pii/S000649712...