The single-dose adenovirus-vectored vaccine Ad26.COV2.S, which encodes the spike protein of SARS-CoV-2, is currently undergoing Phase III testing with the support of Johnson & Johnson. This randomized double-blind Phase III trial, known as ENSEMBLE, has enrolled 45,000 adult participants in multiple countries.

On 29 January, Johnson & Johnson reported interim results from the ENSEMBLE trial, which includes 72% efficacy in the US and 66% overall efficacy against moderate to severe COVID-19.

On 4 February, Johnson & Johnson announced that it had submitted an application to the U.S. Food and Drug Administration (FDA) requesting Emergency Use Authorization (EUA). Later on 4 February, the FDA scheduled a meeting of its Vaccines and Related Biological Products Advisory Committee (VRBPAC) for 26 February 2021. The purpose of the VRBPAC meeting is to have a "public discussion ... about the data submitted in support of safety and effectiveness of Janssen Biotech Inc.’s COVID-19 vaccine ... help ensure that the public has a clear understanding of the scientific data and information that FDA will evaluate in order to make a decision about whether to authorize this vaccine."

For the two SARS-CoV-2 vaccines for which the FDA has already issued EUAs, the EUA was issued the day after the VRBPAC meeting. The VRBPAC meeting on the Pfizer-BioNTech vaccine occurred on 10 December 2020 and the FDA issued an EUA for it on 11 December. The VRBPAC meeting on the Moderna vaccine occurred on 17 December 2020 and the FDA issued an EUA for it on 18 December.

Will the single-dose Johnson & Johnson SARS-CoV-2 vaccine be issued an emergency use authorization by the US FDA within a week after the 26 February VRBPAC meeting?

This question resolves on the basis of an announcement by the US FDA that it has issued an EUA for the one-dose Johnson & Johnson vaccine. Such an EUA should be issued no more than one week after the date of the VRBPAC meeting (no later than 11:59PM EST on 5 March) to count toward resolving this question positively.

If the FDA reschedules the VRBPAC meeting, this resolves ambiguously. If the FDA issues an EUA before the VRBPAC meeting, this resolves ambiguously.