Delta Air Lines said a fifth of its unvaccinated employees received a COVID-19 shot in the two weeks since the airline announced that they would be subject to a $200 monthly surcharge, providing support for companies that are hesitant to impose mandates.

The carrier also hasn’t seen a rise in employee turnover, Chief Health Officer Henry Ting said at a media briefing Thursday. Delta’s employee vaccination rate has increased to 78% from 74% since it became the first major U.S. employer to levy a penalty. Separately, new data from the Society for Human Resource Management found that employees might threaten to quit over a mandate but haven’t really done so thus far.