By Jenny Strasburg

LONDON -- AstraZeneca PLC said it was fixing problems with the manufacturing of its Covid-19 vaccine and expects to roughly double monthly production to 200 million doses by April, as it seeks to move past a rocky start to the shot's rollout.

The Anglo-Swedish drugmaker reported strong full-year earnings and forecast increased 2021 earnings growth. The forecast doesn't factor in sales of the pandemic vaccine it developed alongside the University of Oxford.

Like other vaccine makers, AstraZeneca and Oxford are working on new versions of the shot to target existing and emerging variants of the coronavirus. The drugmaker said Thursday it hoped to reach production of an adapted vaccine at scale within six to nine months, using clinical-trial data and manufacturing agreements already in place.

Last year, AstraZeneca stumbled in communicating clinical-trial results and more recently, suffered a shortfall in doses pledged to the European Union. Chief Executive Pascal Soriot and other executives said Thursday they were working out production kinks and would meet targets to deliver more than 400 million doses to rich and poor countries in coming months. That follows green lights in the U.K., Europe and beyond for the vaccine's use, which isn't approved yet for U.S. use.

This week, the World Health Organization recommended the shot for broad global use, including in countries battling a new strain of the coronavirus first detected in South Africa. Limited trial data have suggested the vaccine is less effective against that version of the virus, though its appears to hold up against a fast-spreading variant first seen in the U.K., particularly against severe symptoms.

The company's difficulties ramping up the vaccine, along with questions about the shot's efficacy, have hit its share price and put executives on the defensive. The two-shot vaccine has been found in clinical trials to be roughly 60% to 70% effective in fighting symptomatic Covid-19, depending on how far doses are spaced apart and other factors.

Adoptions of the shot in December and January were positive for AstraZeneca, but were offset by manufacturing shortfalls that led to a high-profile standoff with European officials in January.

"Is it perfect? No, it's not perfect, but it's great, and tell me who else is making 100 million doses in the month of February," Dr. Soriot said on a call. His executives and he said the vaccine has shown strong protection against severe Covid symptoms and was crucial for preventing hospitalizations and deaths.

Despite the complications of the pandemic and the issues presented by the vaccine, the drugmaker performed well in the past year, analysts said.

"It was critical that [AstraZeneca] demonstrate that the strong momentum of their key business was un-impacted. [They] have not disappointed," Citigroup analyst Andrew Baum said.

AstraZeneca, better known for its established oncology drugs and other treatments, reported $26.6 billion in revenue for the year, a 9% increase from the previous year. Full-year profit after tax of $3.1 billion was more than double the previous year.

It booked $2 million in sales in 2020 from the Covid-19 vaccine, offering the earliest, limited glimpse of the start of its global campaign to roll out 3 billion doses this year. The company has pledged not to profit from the vaccine during the pandemic, or ever, in the case of lower-income countries.

The U.K. was the first to authorize the shot for mass vaccinations, on Dec. 30. An AstraZeneca spokesman said vaccine sales are only booked when doses are shipped, and the $2 million in sales is offset by costs.

The company hasn't offered guidance on expected vaccine sales. In contrast, last week, Pfizer Inc. said it expected its Covid-19 vaccine to generate about $15 billion in sales this year, making it one of the U.S. company's top-selling products. The vaccine, developed with Germany's BioNTech SE, contributed $154 million in sales in the fourth quarter, Pfizer said. The U.S. Food and Drug Administration authorized the vaccine, the first to be cleared for emergency use in the U.S., on Dec. 11.

There is no clear consensus on whether AstraZeneca might eventually profit from the vaccine, or by how much. The company said it would break out Covid-19 vaccine sales separately starting next quarter. The shot is priced at $3 to $5 a dose on average, far cheaper than most vaccines in use or in trial pipelines. Its price and ease of transport, along with AstraZeneca's ambitious production plans, have made it an important part of lower-income countries' hopes to exit from the pandemic.

All vaccine makers face uncertainty around sales of their shots, with new vaccines expected to increase competition, and mutations in the virus causing drugmakers to race to adapt shots. Long-term sales depend on the success of modified shots and the trajectory of the pandemic.

Write to Jenny Strasburg at jenny.strasburg@wsj.com

(END) Dow Jones Newswires

02-11-21 0814ET