| Background & ObjectiveMeasles, mumps and rubella are three common kinds of acute respiratory communicable diseases caused by viruses, which are highly contagious airborne diseases and difficult to control. With the implementation of national immunization programme activities, the incidence and mortality of measles had ever evidently descended. In Zhejiang province, average incidence of measles declined to 6.25 per 100,000 between 1996 and 2000. Currently, the incidence of measles increased again. In Zhejiang province, report incidence rate of measles and mumps in 2004 were 13.10 per 100,000 and 47.79 per 100,000, respectively. Of Zhejiang province infectious disease outbreaks, 20% was mumps. The epidemic situation was very rigorous. Although the incidence of rubella was lower, congenital rubella syndromes (CRS) were serious public hygiene problems. Annually, about 20,000 CRS cases took place in China. Measles, mumps and rubella have similar characteristics of pathogeny, immunity and epidemiology, and World Health Organization (WHO) recommends to control them at the same time with measles-mumps-rubella vaccine (MMR). The birth of Beijing MMR vaccine symbolized that China has already had own MMR vaccine. This paper analyzed epidemiological characteristics and immunization strategies ofthese three kinds of diseases and also involved the safety and immunogenicity of Beijing MMR vaccine so as to provide scientific evidence for immunization strategies.Materials & MethodsCases data was obtained from China legal infectious disease report system, which was renamed recently as China information system for diseases control and prevention, China emergency public reporting system, China measles surveillance system and China surveillance system of information on national immunization program. Population data was obtained from Statistic Bureau and Public Security Bureau of Shaoxing City. Laboratory data was obtained from the microorganism laboratory of Center for Disease Control and Prevention of Shaoxing City. The serum results were provided by National Institute for the Control of Pharmaceutical and Biological Products and Institute for the Control of Pharmaceutical and Biological Products of Beijing city. Cases data was coded according to the county, and the statistical analysis was finished in Excel 2000 and SPSS 10.0 for Windows.Essentialities of combined immunization were researched according to common epidemiological characteristics of these three kinds of diseases. The vaccinated age with the first dose and the time and the key crowd of catch-up vaccination were researched according to age, time, area and occupation distribution. The measles of immunization situation, incidece situation in floating population and babies under 8 months old and serum-test situation were analyzed according to the surveillance system data of close two years. To confirm the vaccinated age with the first does of MMR vaccine, the immunization effects to 8-months-old children with the first dose of Beijing MMR vaccine were analyzed. Quasi-experimental epidemiological approaches were utilized to statistically analyze immunization effect of the vaccine. The vaccine was provided by Center for Disease Control and Prevention of Zhejiang Province.Results1 Epidemiological characteristicsReported cases of measles totaled up to 2890 between 1995 and 2004, however, no death occurred. The average incidence rate was 6.30 per 100,000 annually. In last ten years, the highest and lowest incidence rates were 15.18 per 100,000 in 2000 and 1.25 per 100,000 in 1999, respectively, which has increased again since 2002. The incidence presented the visible seasonal variation as the majority of cases occurred during March and June. The high-prevalence ages were under 1 year and 10~34 years old. The proportion of the adult cases aged over 20 years old increased. The cases aged under 1 year and 1~5 years old accounted for the relatively steady proportion (about 12%). The proportion of out-of-city cases, especially out-of-province cases increased. As for the occuptation, the cases were mainly students and preschool children. Yuechen District had the highest incidence rate among all areas.Reported cases of rubella totaled up to 79 in 2004, however, no death occurred. Reported incidence was 1.82 per 100,000. The incidence presented the certain seasonal variation as the majority of cases occurred during March and June. The high-prevalence ages were 3~9 years and 14~19 years old. Of the total female cases, 45.00% was child-bearing age. The incidence rate of male was lower than that of female but no significant difference was found (w=0.21, p>0.05). As for the occuptation, the cases were mainly preschool children and primary or junior high school students. Xingchang county had the highest incidence rate among all areas.The reported cases of mumps totaled up to 2370 and the number of reported outbreaks totaled up to 6 in 2004, however, no death occurred. Reported incidence was 54.52 per 100,000. The incidence presented the certain seasonal variation as the majority of cases occurred during March and June. The high-prevalence age was 3—13 years old. The incidence rate of male was higher than that of female and strong significant difference was found (m=12.05,/?<0.05). As for the occuptation, the cases were mainly preschool children and primary or junior high school students. Yuechen district had the highest incidence rate among all areas. Three regions and 193 cases were involved in the outbreaks. Six outbreaks took place in five primary schools and one nursery school, respectively. The attack rates were between 3.27% and 15.32%.The incidence rate of male was higher than that of female and strong significant difference was found (u=9.23,p<0.05). Secondary cases appeared in all outbreaks. All cases in the outbreaks had no mumps vaccination records. Only one case attacked with complications of mumps (bronchopneumonia). 2 The immunization strategiesOf the total cases, 22.40% was immunized with measles vaccine and 32.02% was not. The cases delivered two doses accounted for 14.12%. No one was delivered over two doses. Of cases aged between 8 months and 7 years, 37.91% had no measles vaccination records and 39.01% had definite one, while 4.43% was delivered two doses.Between 2003 and 2004, reported cases in floating population totaled up to 143 and the ones aged under 8 months totaled up to 64, which accounted for 18.84% and 8.43%, respectively. The youngest case was 54 days old. These cases in floating population mainly distributed in Yuecheng district and Shaoxing county and the high-prevalence age was between 8 months old and 14 years old. The immunization level of this crowd was low. Of the cases aged under 8 months, the high-prevalence age was 5~7 months old.Serum samples were collected from 40.37% of all suspected measles cases, which were all sampled only once. Of all serum samples, positive rate of specific measles IgM antibody was 63.69%. 202 cases were identified by laboratory test and accounted for 26.61% of all cases.After 91 observation subjects were inoculated, no one had immune reaction within 30 minutes, 2 children had signs of rashes and 2 children had mild local effects within 24~48 hours, 8 children had got transient fever (37.6°C ~ 39.5°C) within 5—9 days. All symptoms were transient and disappeared quickly with symptomatic treatment or without any treatment.Before and after being inoculated, 72 observation objects' serums were tested for HI antibodies of measles and rubella. Before being inoculated, all antibodies were negative. After being inoculated, antibody positive rates of measles and rubella were98.61% and 100%, while GMT were 1: 45.25 and 1: 248.71, respectively.Before and after being inoculated, 70 observation objects' serums were tested for HI antibodies of mumps. Antibody positive rates were 22.86% and 80.00% respectively, while GMT were 1: 1.41 and 1: 4.29 respectively. After being inoculated, the antibody positive rate and GMT of 54 susceptible children was 74.07% and 1: 2.69, respectively.ConclusionsRecently, the incidence of measles is increasing again, and the proportion of the adult case is also increasing. Among the female cases with rubella, 45.00% was women of child-bearing age which indicates the severe situation of CRS in Shaoxing city. Mumps is a serious public hygiene problem because of high incidence and outbreak rate. Because of the similar epidemiological characteristics, MMR vaccine should be added into the routine immunization. Furthermore, other immunization suggestions are as follows: 1) carrying out two-doses immunization schedule, the first vaccination at 8 months old and revaccination between 18 and 24 months old, 2) conducting catch-up vaccination in February foucused on preschool children, students and floating population, 3) improving immunization work quality, 4) strengthening surveillance and laboratory net. |
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