In the fourth large-scale study of an experimental COVID-19 vaccine backed by U.S. taxpayers, Johnson & Johnson is differentiating itself from its competitors by becoming the first in late-stage testing to pursue a one-dose strategy.

Even though the company is weeks behind Moderna Inc., Pfizer Inc. and AstraZeneca PLC in starting its phase 3 trial Sept. 23, J&J will be able to make up time in getting efficacy results because it will not have to wait on study participants to get a second dose like the other three biopharmaceutical manufacturers, which are pursuing a prime-boost approach, said Chief Scientific Officer Paul Stoffels.

J&J could potentially have efficacy data from the phase 3 trial by yearend, Stoffels told reporters. The study is being run by J&J's Janssen Pharmaceutical unit.

Pfizer has estimated it could have data by the end of October.

While it is conceivable there may be efficacy data from for Pfizer's and Moderna's COVID-19 vaccines in October, "I think it's unlikely," said Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, or NIAID.

A more likely timeline for phase 3 efficacy data from the Pfizer and Moderna studies is "sometime in November or December," Fauci told reporters.

He emphasized that the trial results are event-driven, meaning the timeline for getting a look at the data will be triggered by the number of COVID-19 infections reported.

For J&J to reach its efficacy target of 60%, there would need to be 154 infections, Fauci said.

In its phase 3 study, J&J is seeking to enroll up to 60,000 participants — twice as many as Moderna and AstraZeneca. Pfizer initially sought to enroll 30,000 participants but reported Sept. 13 that it planned to expand its trial to 44,000.

Moderna and Pfizer launched their phase 3 studies in late July and the trial testing the vaccine from AstraZeneca and its academic partner, the University of Oxford, got underway a month later.

While Moderna and Pfizer are using messenger RNA platforms for their experimental COVID-19 vaccines, J&J is pursuing an adenoviral vector-based product, similar to AstraZeneca's approach.

J&J's Ebola vaccine, which was granted marketing authorization by the European Commission, is based on the same vector — adenovirus serotype 26, or Ad26, Stoffels said. Ad26 has also been used in J&J's other experimental vaccines aimed at preventing Zika virus, HIV and respiratory syncytial virus, he added.

In preclinical studies, J&J's COVID-19 vaccine — Ad.26.COV2.S, also known as JNJ-78436725 — prevented severe clinical disease in Syrian golden hamsters and elicited an immune response in nonhuman primates, providing complete protection against viral replication in the lungs.

The safety, reactogenicity and immunogenicity of Ad.26.COV2.S are being evaluated in a phase 1/2a trial in the U.S. and Belgium. J&J expects the phase 1/2a interim results to be "published imminently on an online platform," Stoffels said.

Not an overnight achievement

The launch of J&J's phase 3 trial is the result of "fruitful relationships" between the company, the NIAID — part of the National Institutes of Health — and the agency's academic grantees over a number of years, Fauci said.

"These things don't just happen overnight," he said.

U.S. taxpayers have been funding academic research on Ad26 for "literally several years," Fauci said, noting some of that has come from the laboratory of Dan Barouch, a professor of medicine at Harvard University.

The response to the Sept. 11, 2001, terrorist attacks on the U.S. and the concern over bioterrorism helped spur the initial research, Stoffels added.

Fauci said his agency is providing nearly $500 million for J&J's phase 3 study. The NIAID has already spent $193 million on the trial.

J&J is jointly funding the trial, Stoffels added, though he was unable to provide the amount his company is contributing.

J&J is among six companies that have received U.S. contracts under the White House's Operation Warp Speed project to produce COVID-19 vaccines.

J&J received a $1 billion U.S.-taxpayer funded contract in August to make and deliver 100 million doses of the company's vaccine once the product has been cleared for marketing by the U.S. Food and Drug Administration.

Other Warp Speed vaccine contracts include $1.53 billion to Moderna for 100 million doses, $2.1 billion to Sanofi and GlaxoSmithKline PLC for 100 million doses, $1.95 billion to Pfizer for 100 million doses, $1.6 billion to Novavax Inc. for 100 million doses, and $1.2 billion to AstraZeneca PLC for 300 million doses.

Transparency

J&J was among nine vaccine manufacturers that signed a joint pledge to adhere to the highest standard of ethics and not seek FDA clearance until there is sufficient data, Stoffels noted. He said the company is also committed to transparency.

On Sept. 23, J&J became the fourth company to disclose its phase 3 protocol.

Moderna was first to reveal its study's blueprint on Sept. 17. Later that day, Pfizer followed. AstraZeneca disclosed its protocol two days later on Sept. 19.

NIH Director Francis Collins noted that J&J, Moderna and AstraZeneca are sharing a data and safety monitoring board under the agency's public-private partnership. Pfizer elected not to be part of that effort.

Using that strategy across multiple trials will help identify any rare safety signals that may arise, Collins told reporters.