EFFECT OF ORAL POLIOVIRUS VACCINE IN NEWBORN CHILDREN

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Abstract
The stools of 150 breast-fed newborn children who received either Type 1 oral poliovirus vaccine (total of 71) or a mixture of all 3 types (total of 79) during the first 11 to 59 hours after birth, as well as of 35 unvaccinated newborns in the same nurseries in a New York City hospital, were tested for virus. Neither poliovirus nor any other virus was recovered from the unvaccinated. Among the infants who swallowed only Type 1 vaccine, in doses of 1 x 106.7 to 3 x 107.7 TCD50, the excretion rate was influenced by the titer of homotypic maternal antibody—82% among 22 infants with antibody titers of 128 or less, and 42% among 26 infants with titers of 192 or more. The infants who swallowed a mixture of all three types of vaccine excreted predominantly Type 2 poliovirus, and only rarely Types 1 or 3. In contrast to the findings with Type 1, the excretion rate of Type 2 poliovirus by 53 infants was not influenced by levels of maternal antibody ranging from 8 to 2,048. However while 90% of 20 infants who swallowed one or three doses of 107.7 TCD50 excreted Type 2 poliovirus, only 51% of 35 infants who swallowed one or three doses of 106.7 TCD50 excreted. Analysis of our own data on breast-fed children and those of other studies carried out with aliquots of the same lots of vaccine, indicated that the titer of circulating placentally transmitted antibody did not by itself affect the multiplication of the ingested polioviruses in the intestinal tract. The ingestion of antibody-containing milk and the residual amniotic fluid, which may contain antibody especially when the level of maternal antibody is high, are factors of special importance. The very high gastric acidity present in most newborn infants during the first 24 hours appears to have no effect when very large doses of virus are swallowed, but cannot be disregarded when the smaller doses, ordinarily effective in older children are used. When undiluted vaccine was merely swabbed on the posterior pharyngeal wall, 63% of 43 newborn infants excreted virus in the stools, but only 25% of 24 tested yielded small amounts of virus in swabbings obtained from the throat. Only about 35% of 26 infants who excreted Type 1 virus and 59% of 29 infants who excreted Type 2 virus showed evidence of active antibody formation at 3 months of age—largely due to the low levels of antibody produced by the immunologically immature infants and the masking effect of the residual, placentally transmitted antibody.

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