Researchers have demonstrated that aerosol-delivered vaccines based on poxviruses are safe and effective in a trial on monkeys.
Aerosol vaccines have been hailed for their potential in the developing world, where lack of trained personnel, problems with hygienic supplies and social acceptance issues are barriers to conventional, injected vaccines.
The study authors say the method could be particularly useful in vaccinating against diseases that enter the body through mucous membranes, such as genital herpes, human papilloma virus, hepatitis B and HIV.
Their study, published in the Proceedings of the National Academy of Sciences last week (11 February), illustrates that the aerosol method works as a way of delivering vaccines for such diseases.
The researchers tested for safety and immune response using two vaccines, one based on an experimental HIV vaccine and the other a human papilloma virus (HPV) vaccine.
Rhesus macaque monkeys were administered the vaccines in an aerosol preparation, delivered through a nebulizer — a device that turns liquid medication into vapour — and face mask.
The scientists found that the vaccines were safe and absorbed mainly into the respiratory tract and lungs, rather than the brain or eyes where they could cause damage. They also elicited a "robust and long lasting" immune response.
Jean-Pierre Kraehenbuhl, senior scientist at the Eurovacc Foundation at the Swiss Institute for Experimental Cancer Research (ISREC) and coordinator of the study, says the benefit of aerosol vaccines is that they provide immunity both in the mucosal tissue that pathogens invade and the rest of the body. Most injected vaccines don't provide mucosal immunity.
Kraehenbuhl told SciDev.Net that the next step for the research is phase I clinical trials in humans, due to start this year. These will analyse how the vaccine is distributed in human lungs.
There is already an ongoing clinical trial for a measles aerosol vaccine, part of a WHO-led project.
Andrew Hall, professor of epidemiology at the UK-based London School of Hygiene and Tropical Medicine, says the paper demonstrates that the aerosol route can be applied to other vaccines besides those tested for measles.
"Most interestingly this could result in some immunity at other mucosal sites", he says, but adds that it is unclear at this stage whether the immunity would be protective.
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Proceedings of the National Academy of Sciences 105, 2046 (2008)