Timeliness of MMR vaccination and barriers to vaccination in preschool children.

The documented vaccine coverage rate of measles-mumps-rubella (MMR) vaccination is almost 99% in Korea, but measles cases are constantly being reported. This study evaluated the vaccine coverage, timeliness, and barriers to immunization of measles vaccination in preschool children in Korea. We assessed 452 children aged 15-23 months and 300 children aged 4-6 years in September 2007. Questionnaires were administered in order to estimate measles vaccination rate, its timeliness and barriers to vaccine uptake. Being unaware of the necessity for vaccination and its schedule, child being sick during the recommended vaccination period, and recommended vaccination period not being over were significant preventive factors to timely vaccination (P < 0·05). Children with working mothers, single parents, those not being cared for by their parents, and those younger among siblings were at a higher risk of not being vaccinated on time. In order to increase timely vaccination, accurate information should be delivered and a systematic approach should be targeted to high-risk groups.

High tuberculosis transmission rate in children with nursery exposure to undetected pulmonary tuberculosis.

SETTING: Nursery for newborns in Busan, Republic of Korea. OBJECTIVE: To evaluate tuberculosis (TB) transmission from a health care worker with active pulmonary TB to neonatal contacts. DESIGN: For the first investigation, infants who had been in the nursery 3 months before the index patient was diagnosed with pulmonary TB were enrolled. After a child who had stayed in the nursery 10 months before the diagnosis of the index patient was diagnosed with tuberculous meningitis, a second contact investigation was conducted. RESULTS: Respectively 315 and 1334 children participated in the first and second investigations. The mean age of the contacts was 66.3 days; the rate of latent tuberculous infection (LTBI) at the first investigation was 42.5% (134/315). Only one infant had an abnormal chest X-ray, and was thought to have pulmonary TB. In the second investigation, the mean age of the participants was 17.6 months. The proportion of children with LTBI was 18.7% (249/1334). CONCLUSIONS: The LTBI rate in the present study was much higher than that estimated from other contact investigations. To minimise the risk of nosocomial TB transmission to neonates, screening and management of TB in health care workers should be strengthened.

Detection of hepatitis A virus from clotting factors implicated as a source of HAV infection among haemophilia patients in Korea.

To investigate the causal relationship of blood clotting factors and hepatitis A virus (HAV) infection in haemophilia patients during 1998-1999 in Korea, we performed a 1:3 matched case-control study and molecular detection of HAV from clotting factors and patients. The epidemiological investigation showed that one lot of clotting factor VIII was related epidemiologically to patients with hepatitis A with an odds ratio of 35.0, or 38.4 when adjusted for the interval between injections. We examined 17 sera collected from seven patients and 124 lots of blood clotting factors (factor VIII and factor IV) by HAV reverse transcriptase-polymerase chain reaction (RT-PCR). HAV RNA was detected in five clotting factors and six sera. The HAV sequence of one of the factor VIII samples was identical to the sequences found in three patients' sera. Findings from the laboratory and epidemiological studies suggested that the clotting factor was causally related to HAV infection in three haemophilia patients.

A seroprevalence study of poliovirus antibody among primary schoolchildren in Korea.

We aimed to determine the seroprevalence of poliovirus antibody in Korea by using the cell culture neutralization method recommended by the WHO. A total of 500 sera collected from children at eight primary schools in Kyunggi province were used for this study. We found that 82.2% of children were positive for all three types of poliovirus and antibody-positive rates for types I, II and III were 94.4, 96.6 and 86.8% respectively, indicating that seropositive rates for types I and II were considerably higher than for type III (P<0.0001). This result implies that the type III component of the oral polio vaccine should be evaluated further. Although a greater number of children, including young infants, need to be tested for seroprevalence, this study still provides us with valuable information on the effectiveness of vaccination against polioviruses in Korea.