LIVE POLIO IRUS VACCINES

218
Safety-Field Evidence of Safety
POLIOVIRUS
TYPE I
TYPE II
TYPE II!
loo L
100
100
1
3D
.0
CIu
4 u
50
64.5%
50
50
. L'
F-
o
18.1%
182
83 80
45 186
20
375
o
16.3h 19.4%
0 18 375s
45 186 375
Age of Infants ií Days
o
Fic. 4. Percent significant antibody titer responsel at 45, 186, and 375 days of age among infants fed trivalent
oral attenuated live poliomyelitis vaccine on the 5th day of life. 2
1Four-fold or greater rise above the residual level of passively transferred maternal antibody titer at the
same age as calculated by half-life value. Half-life of placentally transferred poliomyelitis antibody is 37 days.
2 All ages are median ages.
infants who showed this delayed response had no
siblings from which a reinfection could be obtained.
It is much less probable that the source
of reinfection is a parent. There is no significant
difference between the per cent showing response
at six months and those showing response at 12
months.
There is stability of the antibody titer between
six and 12 months if a successful vaccination has
occurred. The titer remains at about the same
level plus or minus one tube. These observations
confirm the prediction made in a preliminary
report 1 that an interference or a masking of
antibody response by a high cord blood titer
might be present.
The influence of high and low cord antibody
titers on success of vaccination among newborn
infants as measured at median age of 186 days
is shown in Table 8. Successful vaccination was
achieved among infants with cord titers of 1:256
to 1:1024 in 47 per cent for Type 1; 12 per cent
for Type 2; and 73 per cent for Type 3. This
compares with the per cent of successful vaccination
when the cord titer is 1;128 or less of 89
per cent for Type 1, 25 per cent for Type 2, and
91 per cent for Type 3. The differences between
the numbers of successful vaccinations at the high
and low cord titer levels for Types 1 and 3 are
statistically significant. Infants for whom a
cord blood was not available or the cord antibody
titer was > 1:1024, are not included in Table 8.
The antibody responses of these infants could
not be determined as previously defined.
The per cent of successful vaccination to Type
1 among newborn infants according to dosage
of vaccine used and age of the infant at the time
the vaccination was evaluated is shown in Fig. 5.
There is no striking correlation between the
dosage fed and the success of the vaccination.
This same evaluation for Types 2 and 3 is shown
in Figs. 6 and 7. Again there is no correlation
between success of vaccination and dosage fed.
Injants Age Four Months of Age. The antibody
responses of the 47 infants vaccinated at
median age four months for all three types of
poliovirus are shown in Tables 9, 10, and 11. The
antibody titer four to eight weeks after vaccination
is compared to the residual passively trans-