A new study from Pfizer and BioNTech showed that a booster shot of the COVID-19 vaccine significantly increases protection. The companies are working on a vaccine specifically for the Delta variant, which first appeared in India.

Clinical trials demonstrate that the third dose, given six months after the second, produced levels of neutralizing antibodies five to ten times higher than the first two doses.

“Pfizer and BioNTech are conducting tests to confirm this expectation,” according to the release.

Furthermore, the companies say they want to modify the booster shot to directly target the Indian ‘Delta’ variety as it spreads across the United States. Hence, they intend to release this information as soon as possible and submit it to the Food and Drug Administration for approval.

Until the safety and effectiveness of booster shots can be thoroughly investigated, neither the companies nor the government advocate booster shots. The FDA and the Centers for Disease Control and Prevention issued a joint statement late Thursday emphasizing that people who have been wholly vaccinated do not require booster shots at this time.

“FDA, CDC, and NIH are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary,” according to the government statement. “This process takes into account laboratory data, clinical trial data, and cohort data—which can include data from specific pharmaceutical companies, but does not rely on those data exclusively … We are prepared for booster doses if and when the science demonstrates that they are needed.”

Six months after vaccination, protection against severe disease remained strong, although effectiveness against symptomatic disease starts to decline toward the end of that time, according to the company. The latest information is that this, together with the emergence of new variants, “are key factors driving our belief that a booster dose will likely be necessary to maintain highest levels of protection.”

“As seen in real world evidence released from the Israel Ministry of Health, vaccine efficacy has declined six months post-vaccination, at the same time that the Delta variant is becoming the dominate variant in the country,” the companies said in a written statement.

These findings are consistent with an ongoing analysis from their “Phase 3 study.”

The vaccination still provided significant protection against severe disease, but its efficacy against symptomatic disease had declined due to variations.

“That is why we have said, and we continue to believe that it is likely, based on the totality of the data we have to date, that a third dose may be needed within six to 12 months after full vaccination,” the statement read.

The vaccine, known as BNT162b2, is also being updated to address the Delta variant directly. They are already preparing materials for a clinical trial that will begin in August, pending regulatory permissions.