This international study based in Strasbourg followed 969 lupus patients who got at least one dose of vaccine, with the goal of monitoring them for lupus flares due to the immune activation from the vaccine.
The most common vaccines were Pfizer (57%), Sinovac (22%), AstraZeneca (10%), and Moderna (8%).
45% of patients had some form of vaccine reaction (same day or next day) after the first dose, and only about half of the patients decided to go ahead with the second dose. So only half of this group was fully vaccinated. Of those that had some vaccine reaction, about 1 in 5 reported that it was severe enough to disrupt daily activities.
Only 3% of patients developed a lupus flare, and there was a strong correlation (5-fold increase in risk) between those who had had a flare in the past year and those who had a flare after vaccination. Since there was no control group, there is no way to tell how many of them would have had a flare anyway, but it's plausible that they were caused by the immune activation.
The rate of flares was highest after Moderna (8%) and lowest after Pfizer (2%) but the number of people who got Moderna was small enough that this difference was not statistically significant.
Overall, I think that this is good news for those with well-controlled lupus who have been waiting for data before proceeding with vaccination. It does make sense to be on the lookout for a flare so that you can seek medical attention if it does happen.
Link to study.