Delta Air Lines’  (DAL Get Delta Air Lines, Inc. Report method for pushing its unvaccinated workers to get vaccinated is apparently working.

Two weeks ago, Delta said it would impose a $200 monthly health insurance surcharge on employees who refused to get the vaccine.

In the period since, the company’s vaccination increased to 78% from 74%, Dr. Henry Ting, Delta’s chief health officer, said at an Infectious Diseases Society of America press briefing Thursday, according to news reports.

Delta has 80,000 workers, and nearly 20% of the 20,000 who weren’t vaccinated have now begun the process “which I think is a huge number in terms of shifting that group that’s most reluctant,” he said.

Also, the company hasn’t seen employees quit as a result of the policy, he said.

Delta shares recently traded at $41.08, up 4%.

In other news for the company Thursday, it said in a Securities and Exchange Commission filing that for the third quarter, “adjusted total revenue, excluding third-party refinery sales, is expected to be at the lower end of the prior guidance range, as the recent rise in Covid cases is suppressing demand in the second half of the quarter.”

It expects adjusted revenue of $12.51 billion for the quarter. The prior guidance called for a decline of 30% to 35%.

“During the quarter, demand exceeded expectations in July,” Delta said. “In early August, the pace of recovery paused due to the sharp rise in Covid cases.”

Further, “the pace of business travel recovery has paused, as companies delay or scale down initial office reopenings.”