Moderna said on Thursday its Covid-19 shot was about 93 percent effective through six months after the second dose, showing hardly any change from the 94 percent efficacy reported in its original clinical trial.
That compares favorably to data from Pfizer Inc and BioNTech SE last week in which they said their vaccine's efficacy waned around six percent every two months, declining to around 84 percent six months after the second shot.
Both the Moderna and Pfizer-BioNTech vaccines are based on messenger RNA (mRNA) technology.
"Our Covid-19 vaccine is showing durable efficacy of 93 percent through six months, but recognize that the Delta variant is a significant new threat so we must remain vigilant," Moderna Chief Executive Stéphane Bancel said.
However, a booster dose will be necessary prior to the winter season as antibody levels are likely to wane, Moderna said.
The comment comes as public health officials across the world debate on whether additional doses are safe, effective and necessary even as they grapple with the fast-spreading delta variant of the coronavirus.
Separately, Moderna said its studies of three different booster candidates induced robust antibody responses against variants, including the Gamma, Beta and Delta variants.
It said neutralizing antibody levels following the boost approached those observed after the second shot.
For this year, Moderna has signed vaccine contracts worth $20 billion in sales and aims to produce between 800 million and 1 billion doses.
It has agreements for $12 billion in 2022, with options for another roughly $8 billion in sales and expects to produce between 2 billion and 3 billion doses next year.
The company, however, has not been able to keep pace with the production of much larger rival Pfizer, which expects to manufacture as many as 3 billion doses this year, and expects 2021 sales to top $33.5 billion. Moderna's vaccine was authorized for emergency use in adults in the United States in December and has since been cleared for emergency or conditional use in adults in more than 50 countries.
The company started the process of filing for full approval with the U.S. Food and Drug Administration in June and expects to finish its submission in August.
It posted second-quarter sales of $4.4 billion, slightly above the expectation of $4.2 billion drawn from 10 analysts polled by Refinitiv. Its Covid-19 shot is the firm's first authorized product and sales were just $67 million a year earlier.
Moderna earned $2.78 billion, or $6.46 a share, beating quarterly expectations of $5.96 a share.