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Why is Janssen starting a clinical trial with two doses?

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Janssen Pharmaceuticals, part of Johnson & Johnson, has designed a COVID-19 vaccine candidate to be delivered in a one-dose regimen. The company is also starting a clinical trial for a two-dose regimen. Johnson & Johnson announced that the new phase 3 trial for a two-dose regimen has been planned to be complementary and run in parallel with the ongoing phase 3 trial for a one-dose regimen, erring on the side of caution in case two doses have the "potential to offer enhanced durability in some participants." The existing phase 3 trial for a one-dose regimen, called ENSEMBLE, has been enrolling participants with a goal of testing the Janssen vaccine candidate with up to 60,000 people from multiple countries around the world. The newer phase 3 trial for a two-dose regimen, called ENSEMBLE 2, intends to test two doses of the Janssen vaccine candidate with up to 30,000 participants from multiple countries around the world. These ENSEMBLE and ENSEMBLE 2 trials follow the promising interim results from the phase 1/2a clinical trial of the Janssen vaccine candidate, which has been studying both one-dose and two-dose regimens for preliminary data on safety and effectiveness. Due to the urgent nature of the COVID-19 global pandemic, many phases of vaccine development and testing have been implemented in parallel. For example, sometimes clinical trial phases are combined into a phase 1/2 or 2/3 trial, or a later phase trial is started in parallel based on promising interim results of an earlier phase trial (rather than doing trials sequentially that wait for an earlier phase trial to be completed before starting a later phase trial). Johnson & Johnson is not the only major vaccine developer to be running clinical trials in parallel. Scientists will be able to say more about the effectiveness of the one-dose and two dose regimens after more data from the parallel phase 3 trials become available.

This article was published on
January 6, 2021

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Janssen Pharmaceuticals, part of Johnson & Johnson, has designed a COVID-19 vaccine candidate to be delivered in a one-dose regimen. The company is also starting a clinical trial for a two-dose regimen. Johnson & Johnson announced that the new phase 3 trial for a two-dose regimen has been planned to be complementary and run in parallel with the ongoing phase 3 trial for a one-dose regimen, erring on the side of caution in case two doses have the "potential to offer enhanced durability in some participants."

The existing phase 3 trial for a one-dose regimen, called ENSEMBLE, has been enrolling participants with a goal of testing the Janssen vaccine candidate with up to 60,000 people from multiple countries around the world. The newer phase 3 trial for a two-dose regimen, called ENSEMBLE 2, intends to test two doses of the Janssen vaccine candidate with up to 30,000 participants from multiple countries around the world. These ENSEMBLE and ENSEMBLE 2 trials follow the promising interim results from the phase 1/2a clinical trial of the Janssen vaccine candidate, which has been studying both one-dose and two-dose regimens for preliminary data on safety and effectiveness.

Due to the urgent nature of the COVID-19 global pandemic, many phases of vaccine development and testing have been implemented in parallel. For example, sometimes clinical trial phases are combined into a phase 1/2 or 2/3 trial, or a later phase trial is started in parallel based on promising interim results of an earlier phase trial (rather than doing trials sequentially that wait for an earlier phase trial to be completed before starting a later phase trial). Johnson & Johnson is not the only major vaccine developer to be running clinical trials in parallel.

Scientists will be able to say more about the effectiveness of the one-dose and two dose regimens after more data from the parallel phase 3 trials become available.

Context and background

On November 15, 2020, Johnson & Johnson announced the initiation of a new phase 3 trial for a two-dose regimen of its Janssen vaccine candidate, to run in parallel with the ongoing phase 3 trial for the one-dose regimen. This caught the attention of the media, because the Janssen vaccine candidate has been notable for being a one-dose vaccine, when several other major vaccine candidates (including Pfizer and BioNTech, Moderna, Oxford and AstraZeneca) are designed for a two-dose regimen. A one-dose vaccine has advantages in terms of cost as well as ease of distribution, which could be helpful during the global pandemic.

Some people were concerned that the new two-dose trial could indicate that the earlier one-dose trial results were disappointing in some way. In fact, the preliminary results found that "a single dose...induced a strong neutralizing antibody response in nearly all participants aged 18 years and older and was generally well-tolerated." Johnson & Johnson says that the new two-dose trial is designed to be complementary to its ongoing one-dose trial, providing additional data to help scientists and regulators make decisions about vaccine candidate's use.

Resources

  1. Johnson & Johnson Initiates Second Global Phase 3 Clinical Trial of its Janssen COVID-19 Vaccine Candidate (Johnson & Johnson)
  2. J&J, erring on caution, tests new 2-dose regimen for COVID-19 vaccine (FierceBiotech)
  3. J&J launches Phase 3 trial for 2-dose COVID-19 vaccine (BioPharma-Reporter)
  4. Johnson & Johnson Posts Interim Results from Phase 1/2a Clinical Trial of its Janssen COVID-19 Vaccine Candidate (Johnson & Johnson)

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