Tim Wentworth, who formerly headed Express Scripts, a pharmacy benefit manager, was named CEO as of Oct. 23. Walgreens Boots Alliance’s former CEO, Rosalind Brewer, stepped down in late August as the company was struggling with drug and staffing shortages.

Health care is suffering from wider worker dissatisfaction and staffing shortages that are not isolated to drugstores, as the recent Kaiser Permanente strike shows.

The exact scale of the pharmacists’ protest was unclear. Organizers on Tuesday estimated that more than 300 Walgreens locations — out of nearly 9,000 nationwide — were affected by walkouts planned for Monday through Wednesday. A company spokesperson said “no more than a dozen” pharmacies experienced disruptions.

A Walgreens pharmacy manager who helped organize the walkouts told The Associated Press that teams were short-staffed and overworked, especially with the additional demands from the COVID-19 pandemic.

“It’s led to upset customers,” said the organizer, who spoke to the AP on the condition of anonymity for fear of being punished by the company. “It’s led to medication errors, vaccination errors, needle sticks.”

Many Walgreens workers aren’t unionized and the employees who walked out are organizing online. They shared three main requests for the company, the organizer said: to improve transparency about shifting hours and schedules; to set aside training hours for new team members; and to adjust tasks and expectations at each location based on staffing levels.

The organizer said if Walgreens does not address concerns from pharmacy staff, more walkouts could happen at the end of the month.

Walgreens spokesman Fraser Engerman said the company is listening to the employees’ concerns.

“We are committed to ensuring that our entire pharmacy team has the support and resources necessary to continue to provide the best care to our patients while taking care of their own wellbeing,” Engerman said in a statement.

Drugstores across the country are challenged by heavy workloads heading into the busy fall season. And CVS locations in the Kansas City area also saw walkouts last month, after which the company promised to boost hiring.

Many of these underlying concerns about working conditions have been building for years, said Bled Tanoe, a former pharmacist who has been supporting the walkouts on social media. But the COVID-19 pandemic exacerbated the issue by adding new demands like testing and vaccination, without “the proper support for the people behind the counter,” she said.

Brewer, who left in late August, had said the company was limiting hours at 1,100 pharmacies, or about 12% of its U.S. locations. That was down from 1,600 earlier this year, but a company executive has said it doesn’t expect to return all pharmacies to normal operating hours by year’s end.

In a statement, Walgreens Executive Chairman Stefano Pessina said the company had been seeking a CEO with “deep healthcare experience.”

“We are confident he is the right person to lead WBA’s next phase of growth in to a customer-centric healthcare company,” Pessina said.