LIVE POLIO IRUS VACCINES

484 Efficacy-Field Evidence
484 Eficay-Fied Evdenc
cines or divaccine, but three administrations of
the trivaccine produce immunity in almost 100
per cent of cases (Table 1).
A very convenient method in regard to speed
and effectiveness is triple immunization by the
following schedule: monovaccine of Type 1,
divaccine of Types 2 and 3, and trivaccine of
Types 1, 2, and 3, given at intervals of one month.
This schedule produces the maximum immunogenic
effect and requires the same amount of
vaccine as three administrations of monovaccines
followed by revaccination with trivaccine after
one to three months. Its great advantage lies in
the fact that the schedule is completed more
quickly and medical personnel are not required
to give a fourth revaccination (Table 1).
The high immunogenicity of the live vaccine
is due to the multiplication of the vaccinal
viruses in the intestinal canal of vaccinated
children; this follows a regular cycle with maxintum
accumulation of the virus between the
seventh and the 21st day, followed by a gradual
diminution in its concentration during the subsequent
15-20 days.
The multiplication of the virus follows an
extremely regular course, with no interference
from other viruses, and reaches its greatest intensity
in children with previous low level of immunity
to poliomyelitis, growing gradually less
intense in persons with specific antibodies in
their blood prior to vaccination.5
The most important feature of the live vaccine
has been the formation of intense, long-lasting
resistance in the intestinal canal to the subsequent
administration of maximum doses of
homologous virus, which do not multiply intensively
and are quickly eliminated from the
intestinal tract. 6
In rare instances, the later administered virus
proves capable of multiplication but at a con-
TABLE 1. THE IMMUNOLOGICAL ACTIVITY OF THE LIVE POLIO-
VACCINE IN RELATION TO THE SCHEDULE OF IMMUNIZATION OF
NEGATIVE CHILDREN
daccine
Uaccine
Type
Of COlrnts
Number 1o df 4fold
increase
and over
of
¿useod children anted at ode s
virus total negative total 00
Monovaccine 1 227 148 143 96,8
(once) II 6 68 0,0
III 89 68 65 95,6
Divaccine 11 150 70 57 81
(once) III 150 55 44 80
Trivaccine ¡ 169 102 70 68, 7
(once) 11 189 129 97 75
III 189 144 66 45,8
Trivaccine 1 141 84 76 90,5
( twice) II 141 82 81 98,8
III 141 108 82 76
Trivaccine 1
I
141
141
84
82
84
82
100
100
(3 times) III 141 108 94 87
Monouaccine of Typel 1 860 360 Z83 76
+ Dlvacclne
of Types II and lIl II 860 510 463 90
( random ) III 860 432 312 72
Monooaccine of
Type 1 + Dioaccine
of Types II and /il
+ Trivaccine(random)
II 1
IX1
860
860
860
360
510
432
352
507
412
97
99
95