Janssen: Efficacy of the Only Single Dose Vaccine against COVID-19

One single dose of the Ad26.COV2.S vaccine (Janssen) will protect you against symptomatic and asymptomatic SARS-CoV-2 infection. It also resulted effective to prevent severe or critical COVID-19, including hospitalization and death. Safety outcomes resulted similar to other COVID-19 vaccine phase 3 outcomes.

Eficacia de la única vacuna de una sola dosis contra el COVID-19

Janssen vaccine outcomes were published in NEJM 6 months after the first vaccines came out. Compared to others, Janssen offers an undeniable advantage, which is that it only requires one dose. 

The vaccine produced by Johnson & Johnson is a recombinant, replication-incompetent human adenovirus type 26 vector, encoding full-length severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein in a prefusion-stabilized conformation.

It was an international, double blind study which randomized 1:1 to one single dose (5×1010 viral particles) or placebo. Primary end point was vaccine efficacy against COVID-19 moderate or severe/critical with symptom onset at least 14 days or 28 days after administration, and patients resulted negative for SARS-CoV-2 at the time of inclusion. 

It included 19630 patients with no prior infection receiving the vaccine and 19691 patients receiving placebo.

Efficacy against moderate and sever/critical infection resulted 66.9% 14 days after administration and 66.1% 28 days after administration. Efficacy was over 80%, considering only severe/critical cases. 

Read also: Abdominal Aortic Aneurysm during the Pandemic: Should They Be Operated or Deferred?

94.5% of patients included in South Africa got infected with this variant, and the vaccine also resulted effective against it (52% and 64% at 14 and 28 days, respectively). Efficacy also was around 80% when considering severe/critical cases against this variant.

Adverse effects were mild to moderate, similarly to other vaccines. 

There were 3 deaths in the vaccine group (not linked to COVID-19) and 16 in the placebo group (5 of COVID-19).


The only single dose vaccine developed by Johnson & Johnson saw around 80% efficacy against COVID-19, even in patients with the South African variant. 

Descargar (PDF, Unknown)

Original Title: Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against COVID-19.

Reference: Jerald Sadoff et al. N Engl J Med. 2021 Jun 10;384(23):2187-2201. doi: 10.1056/NEJMoa2101544.

Subscribe to our weekly newsletter

Get the latest scientific articles on interventional cardiology