The Israel study showing the South African variant may breakthrough the Pfizer vaccine was updated on April 16:
In an update to the study posted on April 16, the researchers noted that within the group of people who received two doses, which comprised eight people, all of the B.1.351 infections occurred within a week to 13 days after the second shot. None of them tested positive for it 14 days or more after the second dose.
"This may imply that there is a short window of susceptibility to B.1.351 infection limited to the immediate two weeks after the second dose – but we cannot be confident that this is indeed the case," Stern and Clalit's Ran Balicer said in an email to Reuters on Sunday.
Source
here. I did confirm this is accurate in the updated study:
Notably, when focusing on the eight B.1.351 cases in the FE group, all tested positive during days 7-13 post the second dose, and none tested positive in days 14+ post the second dose. This observation suggests that increased breakthrough of B.1.351 in our cohort occurs mainly in a limited time window post vaccination. Further research is required to clarify these key issues.
The updated study is
here.
One of the study's authors was saying as much on Twitter, but I was unable to find a reliable source until now. As noted above, that doesn't mean we won't see breakthroughs post 14 days at a higher rate than other breakthroughs. There is good reason to believe that may be the case. But, to the extent we need it, the early results of the Moderna booster show it to be very effective against the South African variant.