Moderna’s COVID-19 vaccine showed promise in protecting against variants in a recent lab study, the company said Tuesday.

Among the variants that the vaccine produced neutralizing antibodies against was the delta strain that has public health officials concerned.

The research was conducted on blood serum from eight participants one week after they received their second dose of the mRNA vaccine.

The study found that vaccine’s antibody response modestly decreased by 2.1-fold for the delta variant compared to the strain that originated in Wuhan, China, in late 2019.

Studies show the delta variant, which was first detected in India, is about 60% more contagious than the alpha variant that was first found in the United Kingdom, and twice as likely to lead to hospitalization. 

The delta variant is now in more than 90 countries. As of last week, the Centers for Disease Control and Prevention said it accounted for 20.6% of the cases in the U.S. and was doubling every two weeks. CDC Director Dr. Rochelle Walensky has said she expects the delta variant to become the dominant strain in the U.S., just as it already has in the U.K.

While Moderna’s study found its vaccine produced neutralizing antibodies against every variant tested, it was more effective against some than others. There was, for example, a minimal 1.2-fold reduction for the alpha variant compared to the original strain, but the decreases for three versions of the beta variant, first detected in South Africa, ranged from 6.9-fold to 8.4-fold.

“As we seek to defeat the pandemic, it is imperative that we are proactive as the virus evolves,” Moderna CEO Stéphane Bancel said in a news release. “We remain committed to studying emerging variants, generating data and sharing it as it becomes available. These new data are encouraging and reinforce our belief that the Moderna COVID-19 Vaccine should remain protective against newly detected variants. These findings highlight the importance of continuing to vaccinate populations with an effective primary series vaccine.”

A preprint of the study, which has not yet been peer reviewed, was published Monday on the website bioRvix. 

Meanwhile, Moderna has been conducting trials on potential booster shots targeting emerging variants.