Pfizer helped save the world with covid vaccines. Now it needs to right itself.

Pfizer had announced several days earlier it was embarking on a $3.5 billion cost-cutting effort, including layoffs. Bourla and the other executives explained the company was positioning for growth.

“Future is bright… but you might get fired," one employee wrote in the video’s chat room, which the company had left open. “Dumpster fires are [always] bright," read another message.

Not long ago, Pfizer was among the most admired companies, a firm that in record time had delivered a vaccine that could protect against Covid-19, and then a drug to ward off bad infections. The products powered Pfizer’s revenue past $100 billion. Employee pride swelled.

This week, the company’s shares fell to their lowest close in more than nine years, capping a stunning fall that year-to-date has obliterated $140 billion in valuation. The company is pulling back on some of its research programs and laying off workers. Morale has shriveled, according to current and former employees.

What led the drugmaker to fall so far so fast is a combination of missteps and misreading of the American public’s behavior. Pfizer overestimated future demand for its pandemic products. After the Covid-19 crisis subsided, sales dried up faster than the company—but not Wall Street analysts—had expected. And Pfizer’s other products, no matter how promising, couldn’t close the gap.

Pfizer isn’t alone in facing disappointing Covid-19 sales. Moderna, too, has confronted a sharp drop for its vaccine. And Pfizer had expected it would need to find new sales as its big-selling products faced competition, prompting the company to develop new products and acquire others.

“Pfizer has initiated a broad effort to realign its cost base across the business to ensure its growth and profitability into the future," a Pfizer spokeswoman said. “Unfortunately, hardworking colleagues and their roles are being impacted, which Pfizer does not take lightly. While we navigate this challenging time, we are focused on providing our impacted colleagues with the resources and compassion they deserve."

The company said it is launching new products that will boost sales, including nine new drug and vaccine approvals this year, and has a strong pipeline of drugs that could add further revenue.

Pfizer also said its deal-making, including an acquisition of cancer-drug biotech Seagen that closed on Thursday, could generate $25 billion in new revenue by 2030.

Pfizer’s falling fortunes differ sharply from the company’s spirited sprint during the pandemic, when researchers, manufacturing workers and others mobilized to deliver the world’s first Covid-19 vaccine. Even though the shot was developed with its German partner BioNTech, many people worldwide referred to the vaccine by the name Pfizer.

The company was on top of the world, a household name whose vaccine had allowed economies to reopen and children to return to school. Pfizer celebrated the scientific triumph by handing out commemorative jackets to scientists who had worked on the program, identifying them as members of the Covid-19 research team.

In 2021 and then in 2022, the vaccine surpassed more than $36 billion in annual sales, more than any prescription drug ever had in a single year. Last year, the shot, as well as the Covid-19 drug Paxlovid, powered Pfizer past $100 billion in sales. The company’s valuation surged.

The future looked bright. Pfizer settled in for a long-term Covid business, assuring Wall Street for several years that it expected vaccination trends eventually to mirror those of flu shots, so there would be an annual and predictable source of sales.

Pfizer kick-started multiple programs that could yield future Covid-19 products. For 2023, it set high expectations, telling Wall Street to expect $8 billion in Paxlovid sales and $13.5 billion from the vaccine.

It said it had based its estimates on the infection and vaccination rates for coronavirus, flu and other respiratory diseases.

Its forecasts were higher than what most analysts expected, however. Then it turned out the company had misjudged what demand would be like after the Covid-19 threat diminished. Many people who got shots previously now no longer felt protection from a booster was needed. Others were simply fatigued from getting vaccines. Vaccinations had also become a political issue.

Only 17% of people in the U.S. ages 18 and older have received one of the latest boosters, according to the Centers for Disease Control and Prevention. Use of Paxlovid dropped so much that the government returned millions of pills to Pfizer.

The company is now estimating $12.5 billion in Covid-19 vaccine and drug sales in 2023, and $8 billion in Covid-19 vaccine and drug sales in 2024.

Likewise, Moderna, which notched $18.4 billion in sales of its Covid-19 vaccine in 2022, expects the figure to be at least $6 billion this year.

Pfizer’s pandemic success had, in some ways, hidden a reckoning the company knew was coming. Executives had been warning that some of its top-selling drugs were getting older and nearing the end of patent protection, when lower-priced generics could compete with them.

The company was going to have to find new products whose sales could make up the difference, because it had spun off divisions, like its off-patent and consumer-health businesses, that produced steady revenue but weren’t growing as quickly.

Bourla and other executives talked up a company pipeline that they vowed would deliver the new, faster-growing medicines. Buoyant sales of its Covid-19 vaccine, called Comirnaty, and its drug Paxlovid had helped Pfizer pick up the slack while it waited for new medicines to pass testing and make it to market.

The Covid-19 products’ rapid falloff, however, abruptly ended Pfizer’s good fortune. Investors especially punished the company when, in October, it lowered its 2023 sales forecasts for the vaccine, drug and the company overall.

The stock also fell recently when Pfizer released disappointing study results from an experimental weight-loss pill, which could have given the company entry into the hot anti-obesity market.

Shares closed on Thursday at $26.13, their lowest in more than a decade. This year to date, the stock is down 49%. The decline in its market cap is its largest on record, surpassing the previous record yearly loss of $67 billion in 2004.

Bourla, who had been celebrated around the world for pushing Pfizer to move quickly to combat the coronavirus, now confronts concerns on Wall Street about the company’s sales forecasting and its ability to launch new drugs and deliver on its pipeline.

A Pfizer spokeswoman said the company updates the progress of its pipeline during quarterly earnings.

After Pfizer issued 2024 guidance on Wednesday, Bourla said the company was taking a conservative approach to its forecasting and was taking steps to rev up sales.

“We are very focused on addressing uncertainty and providing clarity. Pfizer’s business is robust, with many in-line acquired and expected launch products that we believe are capable of driving strong revenue," he said.

But analysts expressed doubts. “Based on our conversations, we expect that investors will have a hard time stepping into the story until they gain further clarity," JPMorgan Chase analysts wrote.

Among the new sources of growth Bourla has pointed to is Pfizer’s $43 billion acquisition of biotech Seagen.

Executives have said the deal adds cutting-edge cancer drugs and technology with large sales potential. Bourla has reorganized the structure of the company, creating a separate cancer-drug business, which he told analysts would spur strong performance.

After embarking on the multibillion-dollar cost-cutting program, Bourla also faces morale challenges among employees. They have lamented that their company could spend so much, then say it couldn’t afford so many workers, including some no longer needed because of the deal.

“Why not decrease the number of buildings instead of affecting the workforce that are behind amazing breakthroughs?" one wrote during the Oct. 17 town hall.

More than 2,000 workers globally—out of Pfizer’s 83,000 total—have received notifications that they lost their jobs, according to government reports, Pfizer and news reports. Among those leaving are manufacturing workers in Michigan and Ireland, cancer scientists in California, and researchers in Groton, Conn., Pearl River, N.Y., and Sandwich, England.

The company has paused or suspended funding for programs researching vaccines such as a second-generation Covid-19 vaccine and a C. difficile shot, according to company documents reviewed by The Wall Street Journal.

Elsewhere around Pfizer, workers worry they will be next. One tactic employees are using to anticipate layoffs is to monitor their managers’ calendars. They expect firings are coming if they see the calendars start filling with 15-minute meetings, the time it takes for supervisors to share the bad news.

Write to Jared S. Hopkins at jared.hopkins@wsj.com