The evolution of the Covid virus to be more contagious and better at evading immunity is even outpacing innovative mRNA vaccines like Moderna’s. The current generation of vaccines remains essential to protect us from serious illness and death. But when it comes to pollution control, we’re in a situation that’s the equivalent of running at a constant speed on an accelerating treadmill. Now leading scientists are calling for a renewed focus on nasal vaccines, which are given by spraying into the nose rather than by injection. They say nasal vaccines have the best chance of being able to stop the transmission of Covid and reduce infections to a manageable level. “Solving this problem of inducing really effective immunity to block transmission is such an important challenge that it really deserves significant attention and energy, even though it will take some time and effort,” said Dr. Sandy Douglas, a member of the team that delivered the Oxford/AstraZeneca vaccine. Current vaccines trigger a response in the systemic immune system, which helps prevent serious illness once an infection occurs. But a major drawback has been the failure of injectable vaccines to produce immunity in the respiratory tract – so-called mucosal immunity – which is the body’s first line of defense against Covid. Covid Nasal Vaccines “It’s like having guards behind the castle gate instead of having guards in front,” said Benjamin Goldman-Israelow, an infectious disease researcher at Yale. Many now see a nasal vaccine as the most realistic way to achieve nasal immunity and break the chain of Covid transmission. More than a dozen clinical trials of nasal vaccines are underway, including a phase 1 trial of a nasal version of the Oxford/AstraZeneca vaccine. The challenge should not be underestimated, according to Douglas. “To protect against transmission, we’re on the ground that we’re trying to do much better than exposure to the virus naturally does,” he said. There is less experience with nasal vaccines. The most widely used to date is Flumist, AstraZeneca’s flu spray, which uses a weakened flu virus that works by entering the cells of the nasal lining and triggering an immune response. Archie Bland and Nimo Omer take you to the top stories and what they mean, free every weekday morning Privacy Notice: Newsletters may contain information about charities, online advertising and content sponsored by external parties. For more information, see our Privacy Policy. We use Google reCaptcha to protect our website and Google’s Privacy Policy and Terms of Service apply. This kind of vaccine needs to hit a sweet spot where enough virus is given to kick-start the immune system, but not so much that the virus starts replicating and causes the person to become infected (the phenomenon behind a recent spate of of polio in the United Kingdom ). “This is not a path that people are very excited about making a new vaccine,” Douglas said. With new vaccine approaches, there is always the possibility of unexpected side effects, which some companies could prevent. An intranasal flu vaccine used in Switzerland in the 1990s was withdrawn after it was linked to cases of facial paralysis. “The safety profile may well turn out to be better for nasal vaccines, but there’s a bit more of an unknown,” Douglas said. There is also no consensus on how effective a nasal vaccine would need to be to be marketed. “It’s safe to say that a complete or near-complete block of transmission would be preferable,” said Dr. Samuel Wu, the interim chief medical officer of the US-based company CyanVac, which is preparing to pass a nasal Covid vaccine. 2 test. However, a small percentage reduction in transmission can make a big difference in the real world. “A 30% reduction in transmission would result in a 65% reduction in infections after three rounds of transmission,” Wu said. “The more difficult question is how you would actually measure transmission reduction in a clinical trial,” he added. “We have performed a coexistence model to show that our vaccine reduces transmission of Covid in ferrets, but as far as we know no one has attempted to perform such an experiment with human volunteers.” Professor Akiko Iwasaki, an immunologist at Yale, co-founded the company Xanadu Bio to develop a nasal booster vaccine designed to “dislocate” existing circulating immunity (from an injected vaccine) in the respiratory tract, without the need for live virus. The vaccine, which delivers the Covid spike protein in the nose, has offered protection against transmission in animal tests and the team hopes to start a phase 1 trial next year. But Iwasaki says it will take a concerted effort to bring a nasal vaccine to market and called for “Operation Nasal Vaccine Lightning Speed,” an initiative similar to Operation Warp Speed for this stage of the pandemic. “A small academic lab like mine is not equipped with production, regulatory and distribution capabilities,” he said. “This requires adequate support from the public and private sectors.” Douglas agrees. “There are market failures in vaccine development because companies are reluctant to take risks. Not all benefits are reaped for society,” he said. “If they are going to bear the costs and risks without significant public funding, not enough research will be done.”
