New data shows Moderna's vaccine remains highly protective 6 months after shots

• Moderna said Tuesday its vaccine was 90% effective against COVID-19 six months after administration.
• The results were on par with the long-term benefits of Pfizer's vaccine.
• A special booster shot developed for the B.1.351 variant is showing promising preclinical signs.

Moderna's COVID-19 vaccine remains highly protective six months after a person receives their second shot, according to updated data the biotech released Tuesday.

Just over 90% of trial participants who had received their full immunizations half a year ago had not been diagnosed with COVID-19, Moderna reported. The vaccine was even more effective against severe cases of the viral disease, protecting 95% of the trial participants.

In all, 900 cases of COVID-19 have been reported among Moderna's late-stage clinical-trial participants. The company declined to say how many cases were in people who had received the vaccine.

The long-term level of protection is down slightly from the initial rate Moderna reported after its late-stage clinical trial last year. But the data helps show that Moderna's vaccine and the disease-fighting antibodies it helps create have long-term staying power. Because COVID-19 vaccines were moved to the market so quickly because of the pandemic, experts aren't sure how long the shots will remain effective.

Moderna's results are on par with the other messenger-RNA vaccine available to Americans, which is made by Pfizer and its partner BioNTech. That immunization was 91.3% effective at preventing all forms of COVID-19 and 95% effective at preventing severe illness six months after it took effect, Pfizer said on April 1.

More than 85 million doses of Moderna's vaccine have been administered in the US. The biotech has shipped more than 132 million doses worldwide.

Testing booster shots

Moderna is running two clinical trials assessing how its vaccine works in children ages 6 months to 17 years old. The biotech is also testing multiple strategies to address COVID-19 variants that are taking hold in the US.

One of the strategies is to give a third shot, known as a booster, specifically designed to address a virus variant first identified in South Africa.

That new shot boosted the levels of antibodies that could stop the virus in mice, Moderna said Tuesday. That data has yet to be published in a peer-reviewed medical journal.

"The new preclinical data on our variant-specific vaccine candidates give us confidence that we can proactively address emerging variants. Moderna will make as many updates to our COVID-19 vaccine as necessary until the pandemic is under control," Moderna CEO Stephane Bancel said in a statement.