Young Mo Sohn

Efficacy of single-dose SA 14-14-2 vaccine against Japanese encephalitis: a case control study.

BACKGROUND In China, since 1989, an estimated 120 million children have been immunised with the SA 14-14-2 live-attenuated Japanese encephalitis (JE) vaccine at ages 1, 2, and 6 years. A case-control study of licensed vaccine found two doses to be 98% effective. Subsequently, researchers found that single-dose vaccine efficacy was high; we aimed to confirm this result. METHODS During July 11-24, 1999, 160000 doses of JE vaccine were given to children aged 1-15 years, resident in three districts of Nepal. Several cases of JE were admitted to hospital from early August. We obtained names and addresses of cases with serological evidence of a recent infection from Bheri Zonal Hospital, Nepalgunj. We did a matched case-control study and calculated the odds ratio of vaccination among JE cases and age-sex matched village controls. FINDINGS 20 children, aged 1-15 years, were identified whose illness conformed with the JE case definition and were resident in villages receiving the vaccine. None of 20 JE cases had received JE vaccine compared with 326 of 557 age-sex matched village controls. The efficacy of a single dose of JE vaccine was 99.3% (CI 94.9-100%). INTERPRETATION A single dose of JE vaccine is highly efficacious in preventing Japanese encephalitis when administered only days or weeks before exposure to infection.

Effect of single dose of SA 14-14-2 vaccine 1 year after immunisation in Nepalese children with Japanese encephalitis: a case-control study

BACKGROUND In July, 1999, a single dose of live-attenuated SA 14-14-2 Japanese encephalitis vaccine was given to children aged 1-15 years in the Terai region of Nepal. Cases of natural infection occurred almost immediately. Our aim was to assess the long-term protective effect of this vaccination. METHODS In 2000, this same population had a second seasonal exposure to the virus. We therefore did a case-control study to measure the prevalence of vaccination against Japanese encephalitis in 35 patients hospitalised for the disease 1 year after immunisation, and in age-sex matched village controls. FINDINGS Of 35 children resident in Bardiya and Banke districts admitted to the Bheri Zonal Hospital with serologically confirmed Japanese encephalitis, only one had been vaccinated in 1999. In 430 age-sex matched village controls, 234 (54.4%) were vaccinated. We calculated a median unbiased estimate of the odds ratio of 0.0155, with lower and upper confidence limits of 0.0004 and 0.0986. The protective effect of vaccine after 12-15 months was 98.5% (CI 90.1-99.2%). INTERPRETATION Our study provides evidence of sustained high protection afforded by one dose of live attenuated SA 14-14-2 vaccine in Nepalese children.

Primary and booster immune responses to SA14-14-2 Japanese encephalitis vaccine in Korean infants.

Attenuated SA14-14-2 Japanese encephalitis (JE) vaccine has been administered safely and effectively to more than 100 million children in China since 1988 and recently, licensure of the vaccine in Korea has been sought. In the first clinical evaluation of the vaccine outside of China, we monitored side effects in 84 children and evaluated antibody responses to a single dose given as primary JE vaccination in 68 children, 1-3 years old (mean age 27 months). No significant adverse events were noted. Neutralizing antibodies (geometric mean titer [GMT] of 188) were produced in 96% of the 68 subjects. In 10 other children who previously had been immunized with two or three doses of inactivated JE vaccine, the booster administration of SA14-14-2 vaccine produced an anamnestic response in all, with a GMT of 3378. In a comparison group of 25 children previously immunized with two doses of inactivated vaccine, neutralizing antibody titers were detected in 16 (64%). Viral specific IgM was detected in nine primary vaccinees (13%) but in others, IgM may have declined to undetectable levels in the four week postimmunization sample. Live attenuated SA14-14-2 JE vaccine is a promising alternative to the only commercially available JE vaccine for national childhood immunization programs in Asia.

A 5-year follow-up of antibody response in children vaccinated with single dose of live attenuated SA14-14-2 Japanese encephalitis vaccine: Immunogenicity and anamnestic responses☆

Out of 98 subjects who had participated in the 2000 JE vaccination campaign, 69 people were enrolled in the tests of 2004 and 2005 for the evaluation of long term immune response of a single dose of live attenuated SA14-14-2 JE vaccine. 89.9% of study subjects (62/69) had maintained a high level of neutralizing antibody until 2004 as their GMT was measured as 133 (Min 11, Max 2991). Forty-four subjects were still positive in 2005, 5 years after JE vaccination, and their neutralizing antibody positive rate was significantly higher than that of 69 age-sex matched unvaccinated control subjects: 63.8% (44/69) vs. 14.5% (10/69) (P<0.05). Twenty-four subjects (Group 1) who were seronegative for neutralizing antibody at the 2005 test were given a second dose for revaccination in 2006. Also 49 seronegative (Group 2) subjects who were enrolled as a control group in 2005 were given one dose of primary JE vaccine in 2006. Seven days after vaccination, seropositive rate was discovered to be 76.5% (13/17) and 168.52 (Min 38, Max 2173) in Group 1, while no seroconversion in Group 2. On the 30th day, seropositive rate and GMT were 82.4% (14/17) and 392.01 (Min 22, Max 2197) in Group 1, while 75.7% (28/37) and 45.72 (Min 12, Max 505) in Group 2, respectively. We observed the persistence of neutralizing antibody of single dose of live attenuated SA14-14-2 JE vaccine, 89.9% after 4 years and 63.8% after 5 years, and a rapid secondary immune response on the seventh day after booster dose among those who had been seronegative in spite of the first dose of vaccine. Single dose of live JE vaccine could be effective to provide a long-term protection in JE endemic area, where natural boosting is quite probable in the vaccinees. However, further studies should be carried out to support whether one dose of live JE vaccine is sufficient for people in JE non-endemic area.

Transmission of Seasonal Outbreak of Childhood Enteroviral Aseptic Meningitis and Hand-foot-mouth Disease

This study was conducted to evaluate the modes of transmission of aseptic meningitis (AM) and hand-foot-mouth disease (HFMD) using a case-control and a case-crossover design. We recruited 205 childhood AM and 116 HFMD cases and 170 non-enteroviral disease controls from three general hospitals in Gyeongju, Pohang, and Seoul between May and August in both 2002 and 2003. For the case-crossover design, we established the hazard and non-hazard periods as week one and week four before admission, respectively. In the case-control design, drinking water that had not been boiled, not using a water purifier, changes in water quality, and contact with AM patients were significantly associated with the risk of AM (odds ratio [OR]=2.8, 2.9, 4.6, and 10.9, respectively), while drinking water that had not been boiled, having a non-water closet toilet, changes in water quality, and contact with HFMD patients were associated with risk of HFMD (OR=3.3, 2.8, 6.9, and 5.0, respectively). In the case-crossover design, many life-style variables such as contact with AM or HFMD patients, visiting a hospital, changes in water quality, presence of a skin wound, eating out, and going shopping were significantly associated with the risk of AM (OR=18.0, 7.0, 8.0, 2.2, 22.3, and 3.0, respectively) and HFMD (OR=9.0, 37.0, 11.0, 12.0, 37.0, and 5.0, respectively). Our findings suggest that person-to-person contact and contaminated water could be the principal modes of transmission of AM and HFMD.

A Fatal Case of Disseminated Tuberculosis Coincident with Measles-Rubella Vaccination

The authors report a fatal case of disseminated tuberculosis in a 14-yr-old girl, which developed immediately after a measles-rubella (MR) vaccination. Despite a markedly accelerated clinical course which led to death within two weeks, the authors could not identify any possible cause of the tuberculosis aggravation in this case, with the exception of the MR vaccination. The possible role that MR vaccination had on the clinical course of tuberculosis in this case is discussed.