smallpox vaccine and vaccination in the intensified ... - libdoc.who.int

540 SMALLPOX AND ITS ERADICATION
Page
The search for new vaccines 580
Selection of vaccinia virus strains of low patho-
genicity 581
Attenuated strains 583
Inactivated vaccines 587
Production of vaccine in eggs and tissue culture 588
Silicone ointment vaccine 590
Efficacy of vaccination 590
INTRODUCTION
Vaccination against smallpox had been
practised in virtually every country of the
world, and in many on a large scale, when the
Intensified Smallpox Eradicat,ion Programme
was launched in 1967. By its use, smallpox had
already been eliminated as an endemic disease
from all but 31 countries. which constituted
the hard core of the smallpox problem. It was
clear that, in order to implement the pro-
gramme, one of the first tasks of the WHO
Smallpox Eradication unit would be to ensure
that enough vaccine was available, of suf-
ficiently high titre and sufficiently heat-
stable, to ensure that potent vaccine could be
delivered to those needing vaccination in any
place in the world, however remote and
however adverse the environmental con-
ditions.
Traditionally, smallpox vaccine had been
distributed in liquid form, although labora-
tories in France and the Netherlands East
Indies (now Indonesia) had produced air-
dried or freeze-dried vaccines from the 1920s
onwards. Unless refrigerated, liquid vaccine
did not retain its potency for more than a few
days whereas, until it was reconstituted,
freeze-dried vaccine remained highly potent
for over a month at ambient temperatures,
even under tropical conditions. During the
period after the Second World War, freeze-
dried vaccine prepared in France was being
used in francophone Africa and by the mid-
1950s producers in several countries had
developed freeze-dried vaccine production on
a commercial scale. From 1959 onwards
somewhat larger quantities of freeze-dried
vaccine began to be used for smallpox vacci-
nation in tropical countries, but its extensive
use throughout the world dates from 1967-
1968. After 1971 it was the only kind of
vaccine used in any country engaged in a
national smallpox eradication programme.
In May 1980 the Thirty-third World
Health Assembly, after it had declared that
smallpox had been eradicated throughout the
world, recommended that smallpox vacci-
nation should be discontinued, except for in-
vestigators at special risk. By 1985, smallpox
vaccine production had been stopped in most
countries and in no countrv in the world is
smallpox vaccination routinely conducted in
the civilian population. Vaccine reserves are
being kept for emergencies by WHO and by
the health authorities of some 20 countries
(see Chapter 28). Thus smallpox vaccination
has gone full circle. Introduced by Jenner in
1798. it came to be used all over the world
until, with the eradication of the disease that
it was designed to control, its use has now
been abandoned, except for military person-
nel in some countries. Jenner's prediction,
in the paper reproduced in Chapter 6, that
". . . the annihilation of the Small Pox. the
most dreadful scourge of the human species,
must be the result of this practice" has been
fulfilled, making smallpox vaccination
redundant.
An interesting sequel to this history of the
rise and fall of smallpox vaccination is that
vaccinia virus is currently showing consider-
able promise as a vector for genes specifying
protective antigens against a variety of other
infectious agents (see box). If the results
of current research fulfil expectations,
"smallpox" vaccine may make a comeback as a
vehicle for providing simultaneous active
immunization against a number of selected
"
viral or protozoa1 diseases. It has the advan-
tages of heat stability and ease of administration.
but the risk of com~lications will need to
be carefully weighed and perhaps a more
attenuated strain sought (Quinnan, 1985).
In this chapter, various aspects of vaccine
production and vaccination will be described
in terms of practices that came into operation
after the Intensified Smallpox Eradication