Vaccine delivery breakthrough

• Pages: 17-18

Infectious diseases k ill millions of

people every year and children

under the age of five, especially

those in developing countries,

are par ticularly vulnerable. While

significant progress has been

made through global immuniza-

ti on cam pai gns to pr otec t

against many of these diseases,

the delivery of vaccines to target

populations is costly and requires

considerable logistical support.

All v acci nes cu rrent ly rec om-

mended by the World Health

Org aniza tion ( WHO) to tre at

these diseases – DTP (diphtheria,

tet anus, per tussi s (wh oopi ng

cough)), BCG (tuberculosis), oral

polio vaccine (poliomyelitis), yel-

low fever (for countries at risk)

and measles – require cold stor-

age (between 2ºC and 8ºC) to re-

main stable and viable. This can

significantly increase the cost

per dose of these vaccines and

can result in significant vaccine

wastage arising from breaks in

the cold chain. Equally, if not

more importantly, it leads to a

significant proportion of ineffec-

tive vaccines being administered

with consequent loss of life.

Some estimate that up to 40% or

more of vaccines are ineffective

in sub-Saharan Africa. Last year,

British scientists made a break-

through that “offers a simple and

cheap way of making vaccines

stable – even at tropical temper-

atures,” using a technology that

promises to “revolutionize vacci-

nation efforts.”

In ear ly 2010, scientists from the

Jenner Institute, University of Oxford

and from the British company

Nova Bio-Pharma Technologies,

carried out a proof-of-concept

stu dy1s howin g that v acci nes

they are developing can be stabi-

lized for months using Nova’s

patented Hypodermic Rehydration

Injection System (HydRIS).

“Currently vaccines need to be

stored in a fridge or freezer. That

means that you need a clinic with

a nurse, a fridge and an electricity

supply, and refrigeration lorries

for di strib utio n,” e xpla ins Dr.

Matt Cottingham of the Jenner

Institute at the University of

Oxford, lead author of the study.

“If you could ship vaccines at nor-

mal temperatures, you would

greatly reduce cost and hugely

improve access to vaccines,” he

says. “You could even picture

someone with a backpack taking

vaccine doses on a bike into re-

mote villages.”

The team demonstrated that two

diff erent v irus-b ased v accine s

could be stored on sugar-stabi-

lized membranes for 6 months at

45ºC without any deterioration.

Wh en s tor ed a t 37 ºC f or 1 2

months, these vaccines showed

only very small losses in the

amount of viral vaccine re-ob-

tained from the membrane.

“We’ve shown that a very simple

way of heat-stabilizing vaccines

works for two viruses that are

being used as the basis for novel

vaccines in development,” Pro-

fes sor Ad rian H ill o f Oxfo rd

University obser ved. “This is very

exciting scientifically, because

these viruses are fragile. If we are

able to stabilize these, other vac-

cines are likely to be easier.”

The vaccines use live viruses that

have been engineered so that

when they enter the body they

stimulate an effective immune

response without replicating and

causing infection. A long shelf life

for live-virus-based vaccines is

therefore desirable when deliver-

ing these vaccines to patients in

remote areas.

Using this method, vaccines are

mixed with the sugars trehalose2

and sucrose. This mixture is left to

dry slowly on a filter or mem-

brane where it eventually solidi-

fies to form a thin sugary film.

This preserves the active par t of

the vaccine “in a kind of suspend-

ed animation” and protects it

against deterioration even at

high temperatures. By flushing

the membrane with water, the

vaccine is instantly rehydrated.

“The beauty of this approach is

that a simple plastic car tridge,

containing the membrane with

vaccine dried on, can be placed

on the end of a syringe,” explains

Dr. Cottingham. “Pushing a water

solution from the syringe over

the membrane would then re-

lease the vaccine and inject it in-

to the patient.”

17

VACCINE DELIVERY

BREAKTHROUGH

1 Th is research was

funded by the Grand

Challenges in Global

Health par tnership of

the Bill & Melinda G ates

Foundation, with

additional financial

support fr om the

Wellcome T rust.

2 Tr ehalose – is a sugar

associated with the

ability of plants and

animals to withstand

prolonged periods of

extreme dr yness. When

rehydration occurs, its

properties enable

normal cel lular activit y

to resume without the

major, let hal damage

that would normally

follow a dehydration/

rehydration cycle.

Photo: Oxford University

New system offers cheap

way to make vaccines

stable

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