LIVE POLIO IRUS VACCINES

Spread of Vaccine Strain of Poliovirus in Southern Louisiana Communities 149
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RECIPROCAL OF TITER OF NEUTRALIZING ANTIBODY
BEFORE FEEDING
Fir. 3. Titers of homologous neutralizing antibody at the beginning and end of
observation in vaccine-fed children in Morgan City and Franklin.
of excretion in the Morgan City neighborhood is
indicated in the upper half of Fig. 5 which shows
how many children were found excreting virus in
each week of observation. Excretion in the vaccine-fed
children was maximal immediately after
feeding, and declined abruptly after the third
week. Overall, it was more frequent and persisted
longer in the low-titer group. Among the
placebo-fed children, the peak frequency of virus
shedding was in weeks 4 and 5 and again the
overall frequency was greater in the low-titer
group. In the lower half of the figure, comparable
data are presented for Franklin. These
differ from those for Morgan City chiefly in that
infection began earlier in the placebo-fed children
with the peak of shedding in the third week
in the low-titer group.
The pattern of viral spread among Morgan
City families is indicated in Table 4 in which
episodes of infection with P3 or other enterovirus
in each household are indicated by week of onset.
Understandably, P3 virus appeared immedi-