Vaccines S289 1. High avidity (titer higher than 53% which is indicative of immunity) 2. Low avidity (titer lower than 53% which is indicative of susceptibility) Neonates born from susceptible women were tested for rubella-specific IgM in cord blood sera. Results: Out of 325 women, 3 were excluded because they were not actually pregnant and the outcomes of conception were known only for 235 of the 322 pregnancies. Two-hundred-five (87.2%) had high avidity and 30 (12.8%) had a low avidity titer. The outcome of pregnancy in the two groups is depicted in the graph. Discussion: In this study rubella vaccination did not increase the rate of still birth, congenital malformation and abortions in rubella susceptible vaccinated mothers as compared to immune mothers. There was also no significant difference in still birth, congenital malformation and abortions between non-vaccinated and vaccinated pregnant women. P1074 Evaluation of seroconversion to measles vaccine in vaccinated infants in Ibadan, Nigeria O.M. Akinloye, O. Oyedele, O. Akinloye, F. Adu (Shagamu, Ibadan, Osogbo, NG) Objectives: Measles account for more mortality than any other vaccine preventable diseases and responsible for over 10% deaths of children aged below 5 years worldwide. The use of measles vaccine over the last 30 years has however reduced global measles morbidity and mortality. This study was designed to investigate the efficacy of vaccination in Nigeria and to determine if the presence or absence of maternal antibody at the time of vaccination had any influence on the level of IgG produced after vaccination. Methods: Using ELISA kits, the level of maternally derived IgG was determined in 24 infants at age of nine months who reported at the vaccination centre and 6 cord blood samples from the maternity ward of University College Hospital, Ibadan as control group. The children were bled prior to vaccination and six weeks after vaccination. Results: Five of the infants had protective levels of maternally derived IgG while 19 had lost it at the time of sample collection while the control group shows high IgG levels. Six weeks after vaccination all the infants tested had post vaccination protective levels of measles IgG (400–21966 mlU/mL). However, we observed a drop in the IgG level of children with high maternal antibody level after vaccination, although the post-vaccination IgG levels were still higher than others. One of the infants had a dramatic rise in post vaccination IgG (from 367 to 21966 mlU/mL) this prompted the evaluation of pre and post vaccination measles IgM. Two of the children had detectable measles IgM before vaccination and 4 children after vaccination. Conclusion: It is concluded from this study that there is a high vaccine efficacy with measles vaccination in Nigerian infants. The presence of measles IgM in some children reporting for vaccination shows possibility of recent exposure before vaccination. Sustenance of measles vaccine coverage may therefore result to eradication of measles from Nigeria population. P1075 Mumps outbreak in a highly vaccinated school population: a question of vaccine failure? D. Park, J. Kim, M. Nam, H. Kim, J. Sohn, K. Song, M. Kim (Ansan, Seoul, KR) Objective: Despite MMR vaccination, mumps epidemics have increased. The aim of this study is to describe and identify possible reasons for mumps outbreak in a highly vaccinated high school population. Methods: Survey and cohort study of 41 students in a class of high school, Gyeonggi province, Korea were carried out from Mar. to Apr., 2006. Mumps was clinically diagnosed as an illness with 2 or more days of parotid or any other salivary gland swelling. Vaccination records were achieved by questionnaire. Serologic screening study for mumps IgG and IgM antibody (Ab) and mumps IgG avidity test was done with serum samples collected from 2-5 weeks after onset of symptoms. Virus culture and PCR detection for the mumps virus from throat swab specimen, and sequence analysis were performed. Results: Clinical mumps developed in 15 students (attack rate, 36.6%). Among them, 11 patients had been vaccinated single dose, 3 had second dose, and 1 had not. Twenty six students had not developed clinical illness, of which 23 had been vaccinated single dose, 2 had second dose, and 1 is unknown. All of 41 students had mumps IgG Ab. Two of 15 patients had IgM Ab. Virus was isolated in 3 patients. Sequence analysis of virus isolated revealed 99% similarity with Dg1062/Korea/98 strain. Among 15 patients, 11 vaccinated patients have been considered as secondary vaccine failure with high IgG titer and high avidity index (AI, ±32%), an unvaccinated patient as primary infection with high IgG titer and low AI, and 3 vaccinated patients as other infections with low IgG titer and low AI. Among 26 healthy students, 5 vaccinated patients were retrospectively diagnosed as inapparent infection with high IgG titer and high AI, one student as past infection with high IgG titer and high AI, and the remaining students showed low IgG titer and low AI. Conclusions: The overall attack rate of this study is higher than rates of previous reports for a population with vaccine coverage. Secondary vaccine failure did play an important role in this mumps outbreak. Additionally, booster immunisation for mumps should be considered in immunised adolescent persons to prevent further outbreaks. P1076 Immunological evaluation of Vi-CPS-BSA conjugate of Salmonella typhi H. Ahmadi, B. Tabaraiee, S. Siadat, F. Poor Mirza Gholi, D. Norouzian Shamasbi, M. Hedayati (Tehran, IR) Introduction: The role of Vi-capsular polysaccharide (Vi-CPS) in human immunity against infection caused by Salmonella typhi is well known. Purified Vi-CPS can be regarded as a reliable immunogen to control typhoid fever in man. Moreover BSA can be selected as a T-dependent macro-carrier protein in order to conjugate with Vi-CPS. Methods: Vi-CPS was extracted from standard strain of Salmonella typhi Ty6s (CSBPI-B-191) according previously described, by Ahmadi et al, 1999. The Vi-CPS of Salmonella typhi Ty6s was conjugated to Bovine Serum Albumin (BSA-Sigma) according to Mattox et al, 1989. The conjugate was prepared with 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDAC). The conjugate, Vi-CPS and BSA were injected intramuscularly into three group of three rabbit with boosters on days 15, 30 after the primary immunisation. The serum collected on days 0, 15, 30, 45 and 180 were tested by Passive Hemaglutination test for evaluation of antibody production responses in rabbit model. Results: In comparison purified Vi-CPS with Vi-CPS-BSA conjugate, the titer of hemagglutination passive of anti Vi-CPS-BSA conjugate was