Getting another shot of the Johnson & Johnson COVID-19 vaccine substantially increased its protection, the company announced Tuesday.

According to the results of a new clinical trial, two doses of the vaccine boosts immunity to 94% from the 74% offered by a single dose, the company said in a statement.

“Our single-shot vaccine generates strong immune responses and long-lasting immune memory. And, when a booster of the Johnson & Johnson COVID-19 vaccine is given, the strength of protection against COVID-19 further increases,” Dr. Mathai Mammen, global head of Janssen Research and Development at Johnson & Johnson, said in the statement.

Two shots is also 100% effective against a severe bout of disease, the company claimed. But that estimate is not certain, the New York Times reported.

The new data has been submitted to the U.S. Food and Drug Administration. Since the single-dose Johnson & Johnson vaccine was approved in February, nearly 15 million Americans have gotten it, the Times said.

While the protection offered by the Pfizer and Moderna vaccines appears to wane over time, the J&J vaccine seems to hold its efficacy. In a study of nearly 400,000 vaccinated people and more than 1.5 million unvaccinated people, the vaccine showed little signs of waning after five months, remaining 81% effective, the company said.

Last week, an FDA panel recommended booster shots for those 65 and older who received two doses of the Pfizer vaccine. Whether a second dose of the J&J vaccine was needed wasn’t clear until the results of this latest trial were released.

The trial included 32,000 people around the world and compared people who received one dose of the J&J vaccine with those who received two doses. The second shot increased antibodies four times over the first shot, the company said.

Many people got the J&J vaccine more than eight weeks ago. Some research suggests that a longer time between doses offers even better protection, the Times reported.

Another study found that J&J vaccine boosters given six months after one dose might increase protection 12 times during the following months. If that’s true, a second shot given after several months may be even more effective than after eight weeks, the Times said.

More information

Visit the U.S. Centers for Disease Control and Prevention for more on COVID vaccines.

SOURCE: New York Times

Source: HealthDay