TTS/VITT is a serious side effect associated with the J&J and the AstraZeneca vaccine.
According to the CDC, TTS with J&J occurs at a rate of 4 cases per million doses.
In the United States, 9 deaths involving TTS have been causally linked to J&J vaccination.
Use of the J&J vaccine in the United States began on March 2, 2021.
On Tuesday April 13, 2021, the FDA announced that it was studying six cases of TTS in women aged 18 to 48 who had received J&J vaccination 6-13 days prior, one of whom died and another was in critical condition at the time. Administration of the vaccine was paused throughout the United States.
On April 23, 2021, the pause was ended because the risk was low and communicating with the public and health authorities about this risk and how to treat it would improve outcomes.
By this time, the CDC and FDA had identified 15 cases of TTS in the 8 million doses administered, including 3 deaths. The CDC said that the highest risk was among women ages 30-39.
The risk for women under 50 was said to be 7 per million doses and the risk for women over 50 and all men was estimated at 1 per million doses.
The CDC has identified nine deaths causally associated with the J&J vaccine.
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html (last checked 2023-01-22)
More information about the resumption of J&J: