Drawing from de-identified insurance claims data, Johnson & Johnson (NYSE:JNJ) has announced that a single dose of its Ad26.COV2.S vaccine was 79% effective in preventing COVID-19 infections and is 81% effective in preventing hospitalizations associated with the novel coronavirus.

The company also released results from its Phase 3 ENSEMBLE 2 trial, which tested the impact of a booster dose on immunity. The booster was 94% effective when administered two months after the initial injection and led to a four- to six-fold rise in antibodies. When administered six months after the prime dose, the vaccine resulted in 12-fold higher antibody levels four weeks after the booster dose was administered.

Janssen’s ENSEMBLE 2 study also found that a second dose of its vaccine was generally well-tolerated. The side effect profile from the second dose was generally similar to that of the first dose.

The single-dose results were summarized in a MedRxiv preprint study. The study period was from March 1 to July 17, 2021. After breaking out data for states with a high incidence of the Delta variant in June and July, the study showed similar efficacy of 78%.

Drawing on de-identified national insurance claims data, Janssen notes that the research is the most extensive real-world study to date, including 390,000 people who received its vaccine. The study also included 1.5 million controls matched by age, gender, time, location and comorbidities. In addition, study authors attempted to correct vaccine efficacy estimates related to the under-recording of vaccinations in insurance data.

To confirm COVID-19 infections, the study used an ICD-10-CM diagnosis code of U07.1 in 85% of cases, while a SARS-CoV-2 diagnostic PCR or nucleic acid amplification test result was used in the remaining cases.

A separate study from CDC found that a single dose of the vaccine offered 71% protection against hospitalization.

Janssen’s ENSEMBLE trial, which tested a single dose of the vaccine, found that it was 70% effective in protecting against severe/critical COVID-19 28 days after vaccination.