JanssenJohnson & Johnson’s Janssen division (NYSE:JNJ) is planning on requesting expanding the emergency use authorization (EUA) for its Ad26.COV2.S COVID-19 vaccine to include boosters.

The previous EUA covered a single dose of the vaccine.

Despite its initial advantage as a single-dose vaccine, Ad26.COV2.S has failed to match the popularity of the mRNA vaccines from Pfizer and Moderna.

Authorities in the U.S. and EU have linked the vaccine to extremely rare blood clotting episodes. And recently, officials at the European Medicines Agency found another possible link between the vaccine and clotting in deep veins in Ad26.COV2.S recipients, Reuters reported.

A recent CDC study found that a single dose of the Janssen vaccine was 71% effective in preventing hospitalization from COVID-19. By contrast, the two-dose Moderna and Pfizer-BioNTech vaccines were 93% and 88% effective, respectively.

Janssen said an additional dose of Ad26.COV2.S vaccine boosted its efficacy from 72% after the first dose to 94% after the second.

Pfizer and BioNTech have won U.S. authorization to use their vaccine as a booster in some individuals. Moderna is seeking a similar authorization.

On October 14 and 15, FDA will convene meetings of its Vaccines and Related Biological Products Advisory Committee (VRBPAC) to discuss authorization of the Janssen and Moderna vaccine boosters.