Given the low risk to most newborns of Hepatitis B infection, the routine screening during pregnancy to identify at-risk newborns and the availability of HBIG treatment for exposed infants (that is 75 percent effective at preventing chronic infection), coupled with the lack of studies to determine the safety of vaccinating pregnant women and infants, what was the scientific medical rationale underlying the CDC’s decision in 1991 to recommend that all newborn babies be vaccinated?