The speed at which scientists worked to develop the first Covid jabs was unprecedented. Just nine months after the UK went into lockdown, 90-year-old Margaret Keenan officially became the first person in the world outside a trial to receive the Pfizer/BioNTech vaccine. But the virus is mutating, and the emergence of the Omicron variant last month is already focusing attention on the next generation of jabs.So what do we know about the new Covid-19 vaccines? One change is with delivery mechanisms, such as San Francisco firm Vaxart’s vaccine-in-a-pill, and Scancell’s spring-powered injectors that pierce the skin without a needle. But the biggest development is in T-cell technology. Produced by the bone marrow, T-cells are white blood cells that form a key part of the immune system. While current vaccines mainly generate antibodies that stick to the virus and stop it infecting the body, the new vaccines prime T-cells to find and destroy infected cells, thus preventing viral replication and disease. (The current vaccines also produce a T-cell response, but to a lesser extent.)After a recent study published in Nature, scientists said vaccines targeting a T-cell response could produce much longer-lasting immunity, and be better at fighting virus mutations. “The first-generation Covid-19 vaccines were a rapid and massive victory – far greater than we dared predict,” said Danny Altmann, a professor of immunology at Imperial College London. “But they’re only the first generation of quick wins, which is how they should be regarded. Moving forward there are challenges to consider.”Here are some of the companies on the cutting edge of development:Medicago-GSKLast week, Canada’s Medicago and UK-based GlaxoSmithKline announced “positive efficacy and safety results” from a global trial for what they say is the world’s first plant-based vaccine. It is based on a relative of the tobacco plant, used to produce a particle that mimics the virus, and is combined with an adjuvant made by GSK, which boosts general immune response. The late-stage trial, which involved 24,000 adults across six countries, showed the jab had an overall efficacy rate of 71%, rising to 75% against the Delta variant. The study did not include the new Omicron variant.Medicago, majority-owned by Japan’s Mitsubishi Chemical Holdings since 2013 while Philip Morris International holds a one-third stake, is filing for regulatory approval in Canada and is also in talks with US and UK regulators. The World Health Organization has described plant-derived vaccines as “a new and exciting possibility”, cheap to produce and easy to store.VaxartThe Nasdaq-listed biotech firm has developed what it says is the world’s first oral Covid vaccine, which elicits a T-cell response and generates some antibodies in the nose. The firm dosed its first patients in a mid-stage clinical trial in October. It is also testing if the tablet works against Omicron.A larger international trial with 800 participants will follow next year. Full data from the US trial is expected by March. The tablets can be stored without refrigeration, which makes them easier to use around the world and overcomes the problem of needle phobia. “If you give a pill and a glass of water, you can go a lot faster,” says Dr Sean Tucker, who founded Vaxart 17 years ago. “The mucosa is where the virus invades, and if we stop it there, we keep people healthier and fight off this virus and its variants.”ScancellScancell’s needle-free system.The spinout from the University of Nottingham, now based in Oxford, is testing two vaccine candidates that induce antibody and T-cell responses against the original and variant Sars-CoV-2 viruses in 40 healthy volunteers in South Africa. The first patient was dosed in October and Scancell will conduct a further trial in the UK, with the first data from the early-stage clinical trials expected by June.The vaccines have been developed with Nottingham’s two universities, with £2m of funding from Innovate UK, and are based on a modification of Scancell’s DNA vaccine technology. They are given via needle-free, spring-powered injectors that use a narrow stream of fluid to penetrate the skin. Founded in 1997 by Lindy Durrant, professor of cancer immunotherapy at Nottingham University and the firm’s chief executive, Scancell specialises in developing cancer vaccines. It listed in London in 2008. Its two main shareholders are the US health investor Redmile and the Singapore Vulpes Life Science Fund, while Durrant and other management together own 1.8% of the company.EmergexThe Oxfordshire company has developed a T-cell vaccine that will eventually take the form of an easy-to-administer skin patch. It has recruited 26 people for its first human trial in January. The product can last for up to three months at room temperature. Emergex, founded in 2016 by Thomas Rademacher, emeritus professor of molecular medicine at University College London to develop T-cell vaccines is owned by Singaporean venture capital firm Vickers Venture Partners, its management and high-net worth individuals and family offices.The Vaccine GroupThe University of Plymouth spinout, which is part-owned by intellectual property specialist Frontier IP, has developed a herpes-virus-based vaccine that has been shown in animal studies to work against both Covid and Sars. It stimulates a strong T-cell response, would be effective against other variants and could boost other vaccines, says Jeremy Salt, the chief executive, a trained vet who has worked for Pfizer in vaccine development. The group is looking for a commercial partner that can produce the vaccine at scale for human trials next year. It will be given as an injection or as a nasal spray.