LIVE POLIO IRUS VACCINES

182
Safety-Field Evidence of Safety
0
Cr
o
o
o
a-
o
oJ
20
18
16
14
12
10
8
6
4
2
,st VAC.
__· ·___· ·__ _R L-,',
TYPE N 2 VAC.
1
27 INDEX
CHILDREN
1 ," kN-
32 SIBLINGS
c
LI
v>
20
18
16
14
12
o10
8
6
4
2
23 27 31 4 8 12
JULY
16 20
AUGUST
24 28 1 5 9 13 17SEPT
SEPT
FrI. 12. A comparison between the days on which 27 index children excreted Type 3 poliovirus with
the days on which 32 siblings excreted this same virus. The siblings' infections are fairly coincidental
to those of the index children.
(see Fig. 5), spread the most, infecting 55 per
cent of the homotypic negative siblings and reinfecting
about 44 per cent of those who already
had homotypic antibodies (Fig. 8). With Type
1 (see Fig. 7), the response was less with a
spread of 21 and 33 per cent, respectively. With
Type 2, with a low infectivity rate, practically no
spread was noted.
It is to be emphasized again that none of these
siblings were more than five years old, and for
these results to be meaningful, the young age of
the potential hosts in this population should be
kept in mind, as well as the contemporary existing
pattern of interfering non-poliovirus enteroviruses
which found its highest prevalence among
the 12-24-month-old children.
As to the speed with which these attenuated
poliovirus infections spread from the index child
to siblings, these data appear in Figs. 11 and 12.
In some of the families the index child only
excreted the virus for a day or two, and the same
was true with the siblings. In others, virus excretion
continued for two to three weeks (see
Fig. 11 for an example of what happened in a
single family). Data in Fig. 12 record all the days
in which index children excreted virus and all
the days in which their siblings also excreted a
poliovirus of similar type. This is a demonstration
that there was no dearth of polioviruses going
around in these families during the vaccination
period. Figure 13 records the first recognized
day of onset of the index child infection.
It would seem from this last figure that a fair
percentage of the siblings picked up their attenuated
poliovirus from the index child almost at
once with Type 3-indeed 63 per cent of them
picked up the virus within five days from the
known onset of exposure. With Type 1 this almost
simultaneous onset was less, 37 per cent.
The phenomenon of rapid spread which occurs
in a fair percentage of families, can give the false
impression that these infections were derived
from a common extra-familial source, and not as
a result of one human passage within the family.
The observation recalls to the senior author many
previous discussions in pre-vaccinal days, in
which the attempt was made to interpret the
spread of wild polioviruses through families.