The Janssen COVID-19 vaccine – developed by pharmaceutical company Johnson & Johnson (J&J) – has been approved for emergency use authorisation (EUA) by the US Food and Drug Administration (FDA). Unlike the first two mRNA-based COVID-19 vaccines approved for use, by Pfizer and Moderna respectively, the Janssen vaccine is proven effective after only a single dose, and can be safely distributed and stored in standard refrigerator temperatures.

This viral vector vaccine utilises a harmless adenovirus, engineered with genetic instructions that direct infected cells to produce the SARS-CoV-2 spike protein. Once a body begins producing these foreign proteins the immune system learns how to fight back and immunity is generated. The adenovirus used as a delivery device in the vaccine has been genetically modified so it is unable to replicate or cause any disease.

Pooled data from several trials around the world, including in South Africa where new SARS-CoV-2 variants were emerging, suggest the J&J vaccine is strongly effective at preventing moderate to severe disease four weeks after a single dose. While protection varied, from 77% in the US trials to 57% in the South Africa trials, most importantly, the single-shot vaccine conferred 100% protection from hospitalisation and death in all trials, regardless of region.

Read: Pfizer/BioNTech first in WHO list for emergency use COVID-19 vaccine

Unlike the Pfizer and Moderna vaccines, which both require two doses administered several weeks apart to confer complete protection, the Janssen vaccine offers protection 28 days after one-shot, making it significantly easier to vaccinate large volumes of people from a logistical standpoint.

The other major benefit to the J&J vaccine is it can remain stable and effective for up to three months at standard refrigerator temperatures (36-46°F/2 to 8°C). This makes the vaccine significantly easier to deliver to remote regions.

“We believe the Johnson & Johnson single-shot COVID-19 vaccine is a critical tool for fighting this global pandemic, particularly as it shows protection across countries with different variants,” says Paul Stoffels, Johnson & Johnson’s chief scientific officer.

“A vaccine that protects against COVID-19, especially against the most dire outcomes of hospitalisation and death, will help ease the burden on people and the strain on health systems worldwide.”

According to J&J, 20 million doses of the Janssen COVID-19 vaccine will be available in the US by the end of March, and 100 million doses by the end of June. An emergency use application has also been submitted to the European Medicines Agency.