LIVE POLIO IRUS VACCINES

306 Efficacy-Laboratory Evidence
306 Efficacy-Laboratory Evidence
majority of the babies who excreted virus probably
did develop antibodies. Only after a longer
period of observation will it be possible to determine
the frequency of antibody
rate of infection.
responses.
The observations on the three-month-old infants
are presented in the same table. It will be
seen that good antibody responses were noted in
21 of the 37, whereas 16 showed no change. In
no instance did the titer fall to a significant
degree, but it should be noted that the period of
observation is only one month. The influence of
the serum antibody level at the time of immunization
of these infants upon the frequency with
which a rise in titer was demonstrated, is analyzed
in Table 4. It will be seen that 19 of 22
infants with a pre-immunization titer of eight or
less demonstrated a rise, as compared to only two
of 15 of those whose initial titer was 16 or
greater. The highest pre-immunization titer
noted in this group was 256.
The data might be interpreted to mean that
the higher levels of passive antibody prevented
the infant from forming antibody. However, it
would seem to us more likely that the amount of
antibody formed by the infant was in many instances
too little to be reflected as a significant
rise in the face of the large amount already
present. Quantitatively expressed, if the preimmunization
titer was 64, the baby would have
to manufacture 192 units of antibody in order
for the total to add up to a titer of 256, which
would be a fourfold rise in titer.
pH of gastric contents. Just before giving the
vaccine, the gastric content of 39 newborns was
aspirated and its pH determined. The majority
were found to have a pH of between 1.0 and 3.0,
although the range was from 1.0 to 5.8. The variation
from baby to baby was too little to permit
any correlation of the stomach acidity and the
However, no difference has
been noted when the virus was given before, as
compared to shortly after a milk feeding.
Familial spread oj vaccine viruses. The only
data so far collected on spread of vaccine viruses
are those from two families. In one instance, one
of a pair of twins was fed virus, the other was
not. The vaccinated infant excreted virus for
approximately 12 days. On the 12th day the
other twin became infected and excreted for about
two weeks. Virus then re-appeared on the 33rd
day in the feces of the baby who had been fed
originally. Other members of the family, including
two siblings three and four years of age and
the mother and father, did not become infected.
In the second family a four-year-old sibling
became infected three weeks after the vaccinated
infant was brought into the home. The threeyear-old
sibling and the parents did not excrete
virus during an observation period of eight weeks.
SUMMARY
From the limited data so far available it would
appear that when fed in the first day of life, the
Sabin Type 1 poliovirus vaccine establishes an
infection in approximately 80 per cent to 85
per cent of the babies. Infants three months of
age are more uniformly susceptible.
The level of maternal antibody would appear
to have some influence upon the susceptibility
of the infant to infection. Most of those babies
who never were found to have virus in their feces
had maternal antibody levels of 256 or higher.
However, this was not an "all or none" phenomenon
since a number with maternal antibody
TABLE 4. CORRELATION OF THE PRE-IMMUNIZATION NEUTRALIZING ANTIBODY TITER WITH THE
DEMONSTRATION OF A RISE IN ANTIBODY FOLLOWING IMMUNIZATION IN THREE-MONTH-OLD INFANTS
PRE-IMMUNIZATION
ANTIBODY TITER
RISE
ANTIBODY RESPONSE
No CHANGE
TOTAL
8 OR <
16 TO 256
19
2
3
22
-I _ _ _ _ I_ _ __ _
13
15
TOTAL
21 16 37