Janssen COVID-19 vaccine

The Janssen COVID‑19 vaccine, sold under the brand name Jcovden, is a COVID‑19 vaccine that was developed by Janssen Vaccines in Leiden, Netherlands, and its Belgian parent company Janssen Pharmaceuticals, a subsidiary of American company Johnson & Johnson.

It is a viral vector vaccine based on a human adenovirus that has been modified to contain the gene for making the spike protein of the SARS-CoV-2 virus that causes COVID‑19. The body's immune system responds to this spike protein to produce antibodies. The vaccine requires only one dose and does not need to be stored frozen.

Clinical trials for the vaccine were started in June 2020, with phase III involving around 43,000 people. In January 2021, Janssen announced that 28 days after a completed vaccination, the vaccine was 66% effective in a one-dose regimen in preventing symptomatic COVID‑19, with an 85% efficacy in preventing severe COVID‑19 and 100% efficacy in preventing hospitalization or death caused by the disease.

The vaccine has been granted an emergency use authorization (EUA) by the US Food and Drug Administration (FDA) and a conditional marketing authorization by the European Medicines Agency (EMA) and the UK Medicines and Healthcare products Regulatory Agency. In June 2023, the FDA revoked the emergency use authorization for the Janssen COVID-19 vaccine at the request of its manufacturer.

Because cases of thrombosis with thrombocytopenia syndrome and Guillain-Barré syndrome have been reported after receipt of the Janssen COVID‑19 vaccine, the US Centers for Disease Control and Prevention (CDC) recommends "preferential use of mRNA COVID‑19 vaccines over the Janssen COVID‑19 vaccine, including both primary and booster doses administered to prevent COVID‑19, for all persons aged 18 years of age and older. The Janssen COVID‑19 vaccine may be considered in some situations, including for persons with a contraindication to receipt of mRNA COVID‑19 vaccines." In February 2022, Johnson & Johnson announced it has temporarily suspended production of the vaccine though they also noted that it will likely resume at some point in the future and that it will honor all pre-existing contracts that oblige Janssen to supply its vaccine by using the millions of already existing vaccine doses in its inventory where requested.