LIVE POLIO IRUS VACCINES

304
Efficacy-Laboratory Evidence
TABLE 1. DURATION OF EXCRETION OF VIRUS BY NEWBORN AND THREE-MONTH-OLD INFANTS FOL-
LOWING FEEDING OF TYPE 1 POLIOVIRUS (SABIN LSc, 2AB) VACCINE
NEWBORNS
THREE-MONTH-OLD INFANTS
WEEKS AFTER NO. . NO. %
VACCINATION NO. EXCRETING EXCRETING NO. EXCRETING EXCRETING
TESTED VIRUS VIRUS TESTED VIRUS VIRUS
1 120 85 71 21 20 95
2 110 60 55 15 15 100
3 93 37 40 6 6 100
4 75 22 29
5 54 (62)* 16 30 (25)t
6 30 (62)* 7 23 (10)t
7 12 (62)* 5 42 (8)t
* Number in parentheses: Those babies tested + those who were no longer being followed because of consistently
negative specimens.
t Number in ( ) = adjusted % calculated on the basis of babies tested plus those whose stools had been
consistently negative.
more readily infected than that of the newborn.
Relationship of maternal antibody to infection
of the injant. In attempting to determine the
influence of maternal antibody upon the likelihood
of the infant to become infected we have
been handicapped by the fact that all but a rare
mother has a significant level of neutralizing
Type 1 poliomyelitis antibody in her serum.
Thus, few data are available concerning the
response in the absence of antibody and it has
been necessary to consider the data according to
the titer of maternal antibody. Such an analysis
is presented in Table 2. From these data it is
evident that of the 19 babies who failed to
become infected, 13 were born to mothers who
possessed titers of neutralizing antibody in their
sera of 256 or greater. Looked at in another way,
69 women had titers of 128 or less and only six
(9 per cent) of their infants were not demonstrated
to be infected, whereas 19 of 45 (28 per
cent) from mothers with higher levels of antibody,
did not excrete virus. Thus, if the maternal
titer of homotypic antibody is high enough, 256 or
higher, there is apparently some reduction in
susceptibility to poliovirus infection. Of course,
it is possible that sufficient antibody is present in
the secretions of the lower bowel of the infant
to neutralize the virus even though multiplication
is occurring at a higher level. This seems
unlikely, but it can only be evaluated when the
immune response of these infants has been assessed.
It is of interest, however, to note that
a number of infants whose mothers possessed
serum titers of 512 or higher became infected
and excreted virus in excess of a week.
Antibody response of vaccinated infants. Antibody
determinations are available on 24 newborn
infants and 37 infants three months of age. In
the newborns, the antibody titer of the cord-blood
is compared with that of the infants' serum at
three months of age, whereas for the older infants
the serum titer before immunization is compared
with that one month later. In Table 3 it will be
seen that three of 20 newborn infants who excreted
virus demonstrated an eightfold or greater
rise in antibody titer, 15 showed no change, and
only in two had the titer fallen to a significant
degree. On the other hand, none of the four
babies who did not excrete virus, demonstrated a
rise in titer and three showed a significant fall.