Covid: Johnson & Johnson single shot Janssen vaccine shown to work, but not as well as some two-shot rivals

• Video report by ITV News Science Editor Tom Clarke

Johnson & Johnson's one-dose coronavirus vaccine - which the UK has ordered 30 million doses of - has been shown to protect against Covid-19, but not as well as some two-shot rivals, trials have shown.

The single-shot Janssen vaccine was found to be 66% effective overall at preventing moderate to severe illness, and much more protective — 85% — against the most serious symptoms.

Professor Peter Openshaw from Imperial College London: "It's extraordinary news isn't it? It's such a success for the vaccine development field as a whole and to see this announcement that the Johnson & Johnson vaccine - which is on the list of those that have been procured by the UK vaccine taskforce - also looks so effective is wonderful.

"Obviously we need to see the full data, we've only got the press release so far but that's potentially another 30 million doses that have already been pre-comissioned for the UK for yet another vaccine."

What do we know so far about the Janssen vaccine?

Unlike the other three vaccines approved in the UK, the Johnson & Johnson jab only requires one injection for the recipient to receive full protection.

Johnson & Johnson has said it hopes to manufacture one billion doses of the vaccine by the end of 2021.

As a single shot vaccine, the Janssen vaccine - its most common name, taken from the Belgium-based pharmaceutical companies owned by Johnson & Johnson where the vaccine was developed - could solve supply issues and admin headaches.

The Janssen vaccine in numbers:

• 66% effective overall at preventing moderate to severe illness

• 85% against the most serious Covid symptoms.

• 72% effective against moderate to severe Covid-19 in the US

• 57% effective against moderate to severe Covid-19 in South Africa

• 30 million - the number of doses ordered by the UK

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But is 66% enough to protect people?

Prof Kevin Marsh, Co-lead Covid 19 team at the African Academy of Sciences, and Professor of Tropical Medicine University of Oxford, said that, yes, it is

"It is possible that some people will look at the overall reported efficacy of 66% in preventing moderate to severe Covid-19 and focus on comparisons with potentially higher ‘top line’ efficacy reported for some other vaccines. 

"This would be  a mistake. The real headline result is that a single shot vaccine, capable of easy long term storage and administration provided complete protection against hospitalisation and death. 

"This is important because the immediate requirement of vaccination globally is to limit deaths as quickly as possible. 

"While potentially important for all regions, these results are especially encouraging  for Africa and LMIC’s globally where the combination of single shot, ease of storage and protection against multiple variants is critical.”

When will the vaccine be rolled out?

The company said it will file an application for emergency use in the US within a week before applying for approval from abroad.

J&J expects to supply 100 million doses to the US by June, and says it should have supplies ready to ship as soon as authorities give the green light.

The vaccine has not yet been approved - either in the US or elsewhere - and these are preliminary findings from a study of 44,000 volunteers that has not been completed yet.

What outcome did the trials produce?

Researchers tracked illnesses starting 28 days after vaccination – about the time when, if participants were getting a two-dose variety instead, they would have needed another shot.

After day 28, no one who got vaccinated needed hospitalization or died regardless of whether they were exposed to “regular COVID or these particularly nasty variants,” Mammen said. When the vaccinated did become infected, they had a milder illness.

How many doses has the UK ordered?

The UK has ordered 30 million doses of the Johnson & Johnson vaccine.

Unlike the other three approved vaccines, the 30 million doses can inoculate 30 million people because it only requires one injection, while the others require two doses given several weeks apart for full immunisation.

The UK has ordered 100 million doses of the Oxford/AstraVeneca vaccine, 17 million of the Moderna jab and 40 million of the Pfizer/BionNtech one.

If the UK approves the J&J vaccine, the UK would have enough approved jabs to inoculate 108.5 million people - that's 40 million more doses than the population.

The US healthcare conglomerate initiated research for the vaccine in January 2020 and phase three of clinical UK started in mid-November involving around 6,000 people in the UK, and a total of 30,000 globally.

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One man taking part in the Janssen Covid-19 vaccine trials in the UK said one of his reasons for doing so is to “normalise this idea of vaccination”.

Steve Caudwell, 41, from Solihull, was among those who signed up for the trial on Monday and had his first jab on Wednesday at the Queen Elizabeth Hospital in Birmingham.

What are the differences between the Covid vaccines?

Like the Oxford/AstraZenaca vaccine, the Janssen jab is an adenoviral vaccine. These types of vaccines are based on weakened versions of adenoviruses, which are a group of viruses that typically infect membranes of the eyes, respiratory tract, urinary tract, intestines and nervous system, and include the common cold.

J&J’s shot uses a cold virus to carry the spike gene into the body, where cells make harmless copies of the protein to prime the immune system in case the real virus comes along

In contrast, the Pfizer and Moderna vaccines are mRNA types. Traditional vaccines are made up of small or inactivated doses of the whole disease-causing organism, or the proteins that it produces, which are introduced into the body to provoke the immune system into mounting a response. But mRNA vaccines trick the body into producing some of the viral proteins itself.

Will it work against Covid variants?

There were some geographical differences with the vaccine's efficiency.

It worked better in the US, proving 72% effective against moderate to severe Covid-19 – compared to 57% in South Africa, where it was up against an easier-to-spread virus mutation.

J&J has trial sites in South Africa and Brazil in order to test it against the that have emerged there.