LIVE POLIO IRUS VACCINES

Susceptibility of Newborn Infants to Infection with Poliovirus Strains 309
TABLE 1.
DESCRIPTION OF VACCINE FEEDING
SUBGROUPS
Vaccine admistered
Nlmber of babies
Age of
S$ibgroup Vlns Yo. baby L1.ited Detailed
nlber tope D ilution doses (days) study study
1 1 vndiluted 1 2 - 3 10 10
O 1: 1,1 2-3 l 0
b 1 1:10 1 2 - 3 1 O
2a 2 Vndlluted 1 2-3 10 10
b 2 1 :10
I 2 3 15 0
1_ o
2 1:130 1 2- 3 5 o
3a 3 n:iluted 1 2-3 10 10
b 3 1:13 1 2 - 3 1S o
3 1I132 1 2-3 15
L I 1 undiluted 3 2 -3 20 O
S I undilut ed 1 3 5 O
ab I o 0 1
30 S o5
o I 1:3 3 15 o
1
2,?,3 und luted 10 I
b 1,2,3 ndilt d 2 -3 10 10
v none 2 - 3 20 0
To tal - _ 215 60
trivalent vaccine, it was desirable to minimize as
much as possible the opportunity for sibling contact
infection early after vaccine administration
with resulting intrafamilial circulation of virus
and subsequent reexposure of infants to a virus
type which had failed to cause primary infection
because of intertypic interference. Therefore
group 6 babies were all the first-born in the
family.
Vaccine feeding was done in cycles rather than
by subgroup, two babies in each subgroup (a
total of 32) constituting a cycle. There were two
advantages to this method. First, it avoided the
possibility that all babies of a single subgroup
might be fed at a time of a hospital epidemic of
an illness unrelated to vaccination, and false association
of the illness with a specific vaccine
type or schedule. Secondly, it permitted us to
make continuous comparison of results of vaccination
while new recruitment was still going on, and
therefore to modify the protocol if indicated.
Vaccine administration. The vaccine strains
were kindly provided by Dr. Albert B. Sabin
from single large pools of each type designated
LSc, 2ab (Type 1), P 712, Ch, 2ab (Type 2),
and Leon 12 a 2 b (Type 3). As reported by Sabin,
8 these pools contained approximately 108 '° ,
1073, and 107-4 TCDso per ml. of Types 1, 2, and
3, respectively, as titered in Cynomolgus monkeykidney
cell tissue-culture tubes which had had
the serum contained in the growth medium
leached out of the cells, and held in a roller drum
following inoculation. Using Rhesus cell cultures
held in stationary position after inoculation,
Dr. Dorothy Clemmer in our Tulane University
Laboratory
"
obtained titers of 102.6, 10' , and
10624 TCD 50 per ml. for Types 1, 2, and 3, respectively,
in the vaccine lots actually used in this
trial. Prior to the field use of any vaccine, the
stock vials of each type were thawed, emptied,
and pooled, diluted as required in Hanks' BSS,
and put up in 1 ml. quantities (except for trivalent
use) in individual screw top vials which
were then stored at -200 C. until just before use.
A trivalent vaccine dose consisted of 3 ml. containing
1 ml. of each of the virus types, and it
was prepared and stored in that amount.
The vaccine was administered to the babies
without reference to the last meal. A smoothtipped
"medicine dropper" of 1 ml. capacity was
filled with recently thawed vaccine, gently inserted
into the infant's mouth, and emptied by a
combination of slow squeezing of the rubber bulb
and the sucking action of the baby. The vaccine
was not squirted into the mouth, and therefore
no more than a drop or two was ever lost.
Specimen collection and virus isolation. A
venous blood specimen was collected from the
mother at the time of recruitment. Since previous
work in our laboratory T and elsewhere has
indicated that the neutralizing polio-antibody
titers in an infant's umbilical cord serum do not
differ significantly from his mother's, the maternal
specimen will be used as the baseline for
measuring serologic change. A blood specimen
will be collected from each infant at three to
four months of age and again at six months.
These sets will be tested by titration in parallel.
No serologic study has yet been undertaken.
A fecal specimen was collected from almost
every infant at the time of vaccine feeding. Occasionally
this was impossible, and one was procured
by the mother several hours after vaccination,
placed in an ointment jar, and refrigerated
until the nurse's visit. A fecal sample was collected
from every child six days after vaccination.
In addition, certain babies were designated for
"detailed study" (see Table 1), and a series of
specimens collected. From such infants in
groups 1, 2, 3, and 5 (monovalent vaccine feeding),
they were collected on days: 0, 2, 4, 6, 8,