September 14, 2017

expert reaction to a potential method for a multi-dose vaccine

Researchers publishing in Science have created a new 3-D fabrication method that can generate a novel type of drug-carrying particle that could allow multiple doses of a drug or vaccine to be delivered over an extended time period with just one injection.

Dr Kevin Pollock, Honorary Lecturer in Infection, Immunity and Inflammation, University of Glasgow, said:

“This is very interesting work, though the use of micro-particle releasing vaccine components over time is not really new. A slow release is ideal for the maintenance of vaccine responses as it may mean a second or third dose is not necessary.

“The safety aspects of such a delivery mechanism would need to be demonstrated in many animal models and clinical trials and it may be as long as 15-20 years before such delivery systems could be used in vaccines.  It is not yet well understood how the human immune system would response as it is much more used to receiving a single dose, being allowed to recover, and then being immunised again. This demonstrates the difficulty of going from in vitro or in vivo systems using mice to a vaccine, which is ready to be rolled out in the NHS. This group are not even at this point.

“Therefore, there is much work to be done to consider the safety of these vaccines. The approach is laudable as we are not really any closer to a HIV, malaria or tuberculosis vaccine that is really effective.”

Dr Anita Milicic, Senior Scientist, The Jenner Institute, University of Oxford, said:

“Single-dose vaccination has been a long-standing goal of the WHO: since the early 1990s researchers have been trying to create a vaccine formulation that is capable of delivering the equivalent of 2 or 3 prime-boost vaccinations with a single immunisation. Achieving this would circumvent many obstacles that immunisation coverage faces today: non-compliance, missed or delayed doses, logistical problems of vaccine storage and administration in hard to reach parts of the world, wastage of expired/unused doses, and so on.

“The main challenge so far has been to achieve the all-or-nothing effect: a formulation that will remain intact within the body for a desired period of time and then release all of the vaccine at a later date (thus mimicking the prime-boost regimen), rather than slowly release it over time which has been achieved with a number of drugs to date.

“This paper describes a new state-of-the art technology, SEAL, with which it has been possible to ‘package’ the vaccine so that all of it is released within the body only after a certain period of time. Using a mouse model system, the authors have been able to delay the vaccine release for 10, 19 or 45 days, and this work provides proof of principle that single-dose vaccination is possible. More work is now required to prove the safety of this approach and its wider application to different drugs and vaccines in terms of their stability and biological activity following formulation using SEAL. In addition, it is evident that achieving a single dose formulation has required use of exclusive and expensive technology so manufacturing these formulations on a larger scale will represent a challenge in the future. The question remains whether single dose vaccines can be achieved using other more established methods of vaccine formulation and this is something we are currently working on at the Jenner Institute in Oxford.”

* ‘Fabrication of fillable microparticles and other complex 3D microstructures’ by McHugh et al. published in Science on Thursday 14 September.

Declared interests

Dr Kevin Pollock: “I have received an honorarium from Merck for attendance at the International Papillomavirus meeting in Lisbon, 2015.”

Dr Anita Milicic: “We in Oxford are working on achieving the same goal but with different technologies.”