While most coronavirus vaccines require several injections, a new jab – known as the Janssen vaccine – only requires one shot.


However, new trial data has revealed that the vaccine, developed by American manufacture Johnson & Johnson, is not as effective as many two-shot jabs.

Here’s everything you need to know.

How effective is the Janssen coronavirus vaccine?

The jab was found to be 66 per cent effective at preventing moderate to severe COVID-19, but offers high protection against people requiring hospital treatment, trial results have shown.

The firm said the jab was 85 per cent effective in preventing severe disease “and demonstrated complete protection against COVID-19-related hospitalisation and death as of day 28”.

The vaccine worked across multiple coronavirus variants. This including the South African strain which has been worrying scientists, the firm said.

How does the Janssen vaccine work?

Similar to the Oxford vaccine, the Janssen vaccine is an adenoviral vaccine that works by injecting a genetically-modified cold virus into your body.

Although this virus can’t do serious harm, it transports genetic instructions used to create the protein spikes that are found on SARS-CoV-2. Healthy cells can then use these instructions to make their own spikes, which are not harmful by themselves.

The body’s white blood cells will then attack these spikes and develop a ‘memory’ of them. This means the immune system will have a proven battle plan if confronted by the real coronavirus.

The Janssen vaccine is estimated to remain stable for two years at -20°C and at least three months at 2-8°C, which will make the logistics of rolling the jab out easier as it can be stored in a standard fridge. It could be available at designated vaccination sites across the UK, alongside existing vaccines.

How many doses of the Janssen vaccine have been secured?

The UK has ordered access to 30 million doses of the Janssen vaccine from Johnson & Johnson.

When will the Janssen vaccine be rolled out?

To be administered across the UK, Janssen must apply to the Medicines and Healthcare products Regulatory Agency (MHRA). Without approval, it is too soon to estimate when the jab could be used.


What to read more about coronavirus vaccines? Read our full guides to the Valneva, Moderna and Pfizer jabs.


Thomas Ling
Thomas LingDigital editor, BBC Science Focus

Thomas is Digital editor at BBC Science Focus. Writing about everything from cosmology to anthropology, he specialises in the latest psychology, health and neuroscience discoveries. Thomas has a Masters degree (distinction) in Magazine Journalism from the University of Sheffield and has written for Men’s Health, Vice and Radio Times. He has been shortlisted as the New Digital Talent of the Year at the national magazine Professional Publishers Association (PPA) awards. Also working in academia, Thomas has lectured on the topic of journalism to undergraduate and postgraduate students at The University of Sheffield.