Janssen’s single-shot Covid-19 vaccine 85% effective

A Covid vaccine developed by healthcare giant Johnson & Johnson is 85% effective at preventing the most serious coronavirus symptoms after a single dose.

The company said that latest trials - conducted in several countries - also showed that the vaccine was 66% effective at preventing moderate to severe illness.

Britain has already ordered 30 million doses of the jab, which is pending approval by the Medicines and Healthcare products Regulatory Agency.

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How does the jab work?

Like the Oxford vaccine, the Janssen drug uses a modified adenovirus, a harmless, engineered virus that is injected into the patient. The adenovirus DNA triggers an immune response that helps protect the body from Covid-19 infection.

“Unlike other candidates, however, major US trials have focused on its effectiveness as a single dose,” says The Telegraph.

Those trials have found that the jab, which costs around $10 (£7.28) per dose, is highly effective (85%) at preventing the most serious symptoms associated with Covid infection, as well as being marginally less effective (66%) at preventing even the most moderate symptoms.

There was some variation in the drugs efficacy against different strains of the virus, with it being 72% effective against moderate to severe Covid-19 in the US, compared to 57% in South Africa, which is home to a more transmissible Covid variant.

As well as being a single-shot vaccine, “it also only needs to be kept at fridge temperature, making its storage, distribution and handling much easier”, Sky News reports.

The data from the trial will be submitted to regulators, and trials will continue while further information is shared as part of a rolling review. Johnson & Johnson is also conducting a second phase-three trial to look into the effects of two doses of the vaccine.