Severity of measles: a study at the Queen Sirikit National Institute of Child Health.

INTRODUCTION: Thousands of measles cases are reported annually in Thailand even though measles vaccine has been introduced in the expanded program of immunization for every 9-month-old infant for nearly 20 years. Severe cases are admitted to the hospital, usually with complications, some cases lead to death. OBJECTIVES: To study the clinical presentations of severe cases of measles and its complications and find the correlations of severity of pneumonia with age, nutritional status and history of vaccination. MATERIAL AND METHOD: The hospital charts of measles patients admitted to the Queen Sirikit National Institute of Child Health (QSNICH) during 1998-2002 were retrospectively reviewed. Demographic data, history including history of measles vaccination, physical examinations, laboratory investigations, treatment and hospital course which were relevant were recorded. Paired t-test and Pearson's correlation were used for data analysis. RESULTS: There were 156 cases of measles admitted to the QSNICH. There were 95 boys and 61 girls and the male to female ratio was 1.56:1. The age range was 2 months to 14.8 years, median = 1.5 years, mode 8 months. Fifty-nine percent of the cases were under 2 years of age; 40% under one year and 23.9% were under 9 months. About 44% of the cases had one dose of previous measles vaccination, no history of measles vaccination in 91.4% of cases whose age was under 1 year in contrast to 80% of cases over 5 years that had a history of measles vaccination. Sixty-six percent of the cases had normal nutritional status while 12.4%, 4.8% and 2.1% had mild, moderate and severe protein calorie malnutrition. Fourteen cases (9%) had underlying diseases. At least 3 of the classical signs and symptoms of measles (rash, cough and coryza) were found in 92.3% of the cases. The mean duration of fever at the time of admission was 5.3 days. The common complications in admitted measles cases were pneumonia (62.2%) and diarrhea (38.1%). The likely causes of pneumonitis were measles viruses (52.6%) and bacteria (47.4%). There was one dead case with severe pneumonia, with ARDS and respiratory failure. Young infants had a higher incidence of diarrhea with dehydration (p = 0.000) but severity of pneumonia was not different from older children (p = 0.512). The severity of pneumonia was not correlated with the age (r = 0.087), nutritional status (r = 0122) or the history of receiving measles vaccine (r = 0.116). CONCLUSION: Measles is one of the important diseases of in-patients admitted to the QSNICH, because of the severity of the diseases due to pneumonia and diarrhea. One severe case died because of severe pneumonia that lead to ARDS and respiratory failure. Young infants had a higher incidence of diarrhea and dehydration, while there was no correlation between severe pneumonia with age, nutritional status and history of vaccination.

Trend of measles morbidity in Thailand.

RATIONALE: Measles is still an important public health problem in Thailand despite the high coverage of measles vaccination since 1984, and the second dose of measles vaccination in primary school children in 1991. OBJECTIVE: To study the trend of measles morbidity in Thai children. MATERIAL AND METHOD: Review of the Annual Epidemiological Surveillance Report of the Epidemiology Section, Department of Communicable Disease Control, Ministry of Public Health (MOPH), and hospital records of measle cases at the Queen Sirikit National Institute of Child Health (QSNICH) (Bangkok Children's Hospital). Paired t-test and analysis of variance (ANOVA) were used for data analysis in the present study. RESULTS: Before 1984, measles morbidity was very high, at the level of 52.3 to 93.67 per 100,000 population. After measles vaccine was included in the EPI (Expanded Program on Immunization), the morbidity fluctuated for some years, and the group of children infected with measles changed from under 5 years to the age group of 5-9 years old. So a second dose of measles vaccine was added to the EPI given to children in Prathom 1 (first year in primary school, 6 years old and over). After 4 years of adding the second dose of measles in the EPI, measles cases was still present in a significant number in both the under 5 and 5-9 age groups. From the statistics of measles cases at the QSNICH, with an average of 736 measles cases per year, the number of measles cases is now decreasing, but the incidence of measles is still high in both the under 5 and 5-9 age groups. CONCLUSION: According to the EPI in Thailand, children were given measles vaccine at the age of 9 months which is when seroconversion was significantly lower than immunization after one year of age. The trend of measles morbidity is decreasing, but is still high in children in the under 5 and 5-9 age groups. Vaccine failure may be one of the contributing factors of measles cases in children in these age groups. A booster dose of measles vaccine at 15-18 months old is suggested in order to increase the seroprotection in children in the under 5 and 5-9 age groups.

Antibody response after measles immunization.

RATIONALE: Measles is still an important public health problem in Thailand despite measles vaccination being practiced since 1984. Vaccine failure is one of the suspected reasons for the high incidence of measles. OBJECTIVE: To study the seroconversion rate of 9-month-old infants and to study the antibody level in 18 month-old and 4 year-old children who had measles vaccination at 9 months of age. MATERIAL AND METHOD: Enrolled infants and children who attended the child health clinic for routine immunization at the Queen Sirikit National Institute of Child Health from March 1, 1994 to May 31, 1995. They were divided into 3 groups. Group A, 9 month-old infants who came for measles vaccination. Blood samples were drawn twice from these infants, before measles vaccination and 3 months later for measles antibody level. Group B and C were 18 month-old and 4-year-old children who came for their first and second DTP (Diphtheria, Tetanus, Pertussis vaccine) booster. One blood sample for measles antibody was drawn from the latter group of children. Measles antibody was determined by micro-neutralization technic at the National Institute of Health (NIH). The geometric mean antibody titer before and after measles vaccination was compared by using the paired t-test. RESULTS: There were 30, 31 and 34 infants/children in group A, B and C respectively. No significant measles antibody (NT antibody was less than 1:4) was detected in 93.5 per cent of 9-month-old infants. The seroconversion rate at 3 months after vaccination in group A children was 68.75 per cent while in group B, 9 months after vaccination it was 53.3 per cent. Ninety seven per cent of children in group C had NT antibody above 1:4. The geometric mean titer (GMT) of measles antibody in 9-month (before vaccination), 12-month, 18-month infants and 4 year old children was 1:2.5; 1:14.8, 1:8.2 and 1:73.8, respectively (p < 0.05). CONCLUSION: Almost 70 per cent of vaccinees at 9 months of age had seroconversion to measles vaccine with GMT of 1:14.8 while fifty three per cent of 18 month old children had an average GMT of 1:8.2. The GMT of the two groups was significantly different (p < 0.05). At 4 years of age almost all the children had NT antibody to measles with a GMT of 1:73.8 (p < 0.05) Vaccine failure is likely to be one factor responsible for the high incidence of measles after the introduction of measles vaccine into the Expanded Program of Immunization (EPI). The authors suggest giving a booster dose of measles at 15 months of age to boost the antibody level before waning of measles antibody at 18 months old, in order to protect this group of children from contracting measles.