Pregnancy and child

Single-injection vaccine device still a long way off

"Scientists invent injection that could deliver every childhood vaccine in one go," reports The Independent. Various media sources have run stories on a new injection they claim could allow multiple childhood vaccines to be delivered in a single jab.

This follows the development in the US of a method of making a tiny, multilayered biodegradable device, or microstructure, that can be given via injection. The device has several compartments that can be filled with solutions to be released at different points in time.

For the study, mice were given a single injection of the microstructure, which had been loaded with two fluorescently labelled sugar solutions. The researchers showed that the device could release the solutions at different times and that the delivery seemed to be better than in mice who received the solutions via two separate injections.

This device could have great medical potential, but it's important to realise that this is very early research.

More stages of testing in mice would be needed before we could think about human trials. There may be many as-yet-unknown obstacles in terms of safety and effectiveness when considering using the device for human immunisation.

Where did the story come from?

The study was carried out by researchers from the Koch Institute for Integrative Cancer Research at Massachusetts Institute of Technology (MIT) in the US and was funded by the Bill & Melinda Gates Foundation. Individual researchers received various additional funding grants.

The study was published in the peer-reviewed journal Science and is free to read online.

The media reporting was generally representative of the study and discussed the potential applications of such a device, as well as some of the hurdles that still remain.

What sort of research was this?

This was laboratory research describing the manufacture of a 3D microstructure that could be used for pulsed delivery of a drug or vaccine in a single injection.

The authors explained how 3D microdevices could be used for tissue engineering and drug delivery. Depending on size, shape and composition, the internal architecture of 3D microdevices offers greater potential than single-layer devices.

However, this research is still at the early experimental stage.

What did the research involve?

The researchers fully described the technique they used to create the microdevice. The methods are complex and only described in brief here.

The device was made of lactide-glycolide copolymers, the most widely used biodegradable polymers for human applications. The fabrication technique ("StampEd Assembly of polymer Layers" or SEAL) involves the technology used to produce computer chips.

The first layer of the microstructure is created using heated polymers in a silicone mould. This is then repeated, using microscopic alignment, to add layer upon layer to create structures smaller than 400 micrometres.

The process was tested by creating a number of different microstructures, including a 3D star, table and chair.

The researchers' main aim was to produce a microstructure that could be injected into the body and deliver timed pulses of different vaccines or drugs. They made a microstructure with hollow bases, filled these with a test solution and then carried out various experiments.

What were the basic results?

The researchers created a device that could give a controlled release of a substance. It delivered a fluorescently labelled test solution in a separate pulsed release, with no leakage prior to the set release time.

The sealed structures, filled with two labelled sugar solutions set to be delivered in separate pulsed releases, were then injected into a group of mice.

This group was then compared with mice that received the solutions via two separate injections timed to match the release from the microstructures. When tested after one week and then again after one month, levels of the test solutions were higher in the blood of the mice that received the single injection.

The microstructure and its pulse-release capacity were also stable under variations of temperature and acidity.

How did the researchers interpret the results?

The researchers said: "These experiments demonstrate that one injection of core-shell particles can induce a long-term antibody response, outperform multiple time-matched injections, and achieve twofold dose sparing."


Injection of a microstructure device that can give time-delayed release of a vaccine or drug could have great potential in medicine.

As the researchers noted, the structures are tiny and fully biodegradable, so they shouldn't cause a foreign-body reaction.

But they also mentioned the size – the lightweight device could only hold a small amount of solution. However, the researchers suggested that varying the wall thickness to create larger cores could greatly increase the device's capacity.

At this stage, the device has only been tested in a single experiment in mice. Further research in mice would be needed to see whether you could move on to testing it in humans. It's very difficult to stay at this stage which human vaccines the device could potentially be used for or what obstacles there could in terms of safety and effectiveness.

Various experts have given their response to the findings.

Dr Anita Milicic, senior scientist at the University of Oxford's Jenner Institute, said: "Single-dose vaccination has been a long-standing goal of the WHO [World Health Organization]: since the early 1990s researchers have been trying to create a vaccine formulation that is capable of delivering the equivalent of two or three 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."

Dr Kevin Pollock, honorary lecturer in infection, immunity and inflammation at the University of Glasgow, cautioned: "It may be as long as 15 to 20 years before such delivery systems could be used in vaccines.

"It is not yet well understood how the human immune system would respond 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 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."

Find out more about the current childhood vaccination schedule in England.

NHS Attribution