The UK’s medicines regulator has approved the use of a fourth Covid vaccine, as cases of the variant of concern first detected in India rise. The jab from US-based pharmaceutical company Johnson & Johnson is considered a key tool in the global arsenal against Covid, given it is a one-dose regimen, unlike the the other three vaccines approved for UK use that require two shots to provide a high level of protection. The vaccine is based on an approach J&J used successfully against Ebola. It is similar to the Oxford/AstraZeneca jab, but delivers a protein from the spike of the coronavirus through a human common cold instead of a chimp adenovirus. The vaccine, made by the US giant’s Belgium-based subsidiary Janssen, was trialled with more than 44,000 people in the US, South Africa and Brazil. Further trials involving a second dose are taking place in the UK. The British government had initially ordered 30m doses but the order was later amended to 20m. The EU has ordered 400m doses. Late-stage data published in January revealed a 66% efficacy rate in preventing moderate-to-severe Covid 28 days after vaccination. Specifically, the jab was found to be 85% effective in preventing severe disease across all regions studied. It also provided 100% protection against hospitalisation and death, as have other vaccines authorised for use globally. The health secretary, Matt Hancock, said: “This is a further boost to the UK’s hugely successful vaccination programme, which has already saved over 13,000 lives, and means that we now have four safe and effective vaccines approved to help protect people from this awful virus. “As Janssen is a single-dose vaccine, it will play an important role in the months to come as we redouble our efforts to encourage everyone to get their jabs and potentially begin a booster programme later this year.” The J&J vaccine – which is estimated to remain stable for two years at -20°C (-4°F), at least three months of which can be at normal refrigerator temperatures – has been linked to rare but dangerous blood clots with low platelet counts like the Oxford/AstraZeneca jab, with cases occurring in people under 60, mostly women. The UK’s Joint Committee on Vaccination and Immunisation (JCVI) recommended last month that people under 40 be offered an alternative to the Oxford/AstraZeneca vaccine given the blood clotrisk. Whether this recommendation will be expanded to the J&J vaccine remains to be seen, but any decision will not have an immediate impact on the UK’s vaccine rollout because doses are not expected to be delivered until later this year. US health officials lifted an 11-day pause on the vaccine last month after expert advisers determined that the benefits of the shot outweighed the risks. The European Medicines Agency (EMA) has recommended a warning should be added to the vaccine’s product information, but has also stressed that its benefits outweigh its risks.