Learning Objectives for this Presentation:
By the end of this presentation, participants will be able to explain the potential impact of post-vaccination serologic testing in reducing perinatal transmission of hepatitis B disease.

Background:
Giving HBIG and three doses of hepatitis B vaccine to infants born to hepatitis B-infected women can reduce perinatal transmission rates from up to 90% to less than 4%. Recent studies have documented the effect of post-vaccination serologic testing (PVS) in both improving prophylaxis rates and reducing perinatal transmission of hepatitis B.

Objectives:
Assess the impact of PVS among infants enrolled in the California Perinatal Hepatitis B Prevention Program (PHPP).

Methods:
Review of PVS results in PHPP records for infants born 2000-2004 to infected women. We present the number and percent with the outcomes of immunity (HBsAg-negative, Anti-HBs-positive), infection (HBsAg-positive), vaccine non-response (HBsAg-negative, Anti-HBs-negative), and follow-up testing of revaccinated non-responders.

Results:
Of 11,825 infants enrolled, we have PVS results for 6,122 (51.8%). 5,609 infants are immune (91.6%), 129 are infected (2.2%), and 384 did not respond (6.2%). We have record of 197 non-responders beginning a second three-dose vaccination series (51.3%), and a second set of PVS results for 153 (39.8%), resulting in 146 additional immune infants (95.4%) while seven infants remain susceptible (4.6%).

Conclusions:
Revaccination induced immunity in over 95% of infants who did not initially respond to vaccination. At least 146 infants otherwise susceptible to infection during the five-year study period are now immune to future hepatitis B infection. Among 3,000 infants born to HBsAg-positive women in California annually, more than 170 who remain susceptible after an initial vaccination series could be protected through universal PVS and revaccination as indicated. In addition, PVS permits prompt recognition and management of infected infants at risk of developing cancer later in life. Efforts to assure PVS for all infants born to HBsAg mothers are warranted.