Measles immunization in Iran

Mass immunization with live measles vaccine has been carried out in rural Iran since 1968. Two strains have been used: primary baby calf kidney cell-adapted Sugiyama strain and human diploid cell-adapted AIK strain. More than 94% of the susceptible children experimentally vaccinated with either of the two vaccines have shown seroconversion. Mass immunization in rural regions has covered about 80% of susceptible children. It is now recommended that the live vaccine be administered twice: the first dose at six to nine months and the second at 12-15 months of age. In all of 100 cases of subacute sclerosing panencephalitis (SSPE) observed in the Tehran region between 1977 and 1982, the patient had a history of measles infection in childhood; there was no indication that SSPE developed after vaccination. Most of the patients with SSPE have had a high titer of antibody to measles virus in serum and cerebrospinal fluid, and antibody has commonly been demonstrated in saliva as well.     

An investigation into a measles outbreak in southeast Iran

In 2009 and 2010, a series of measles outbreaks, involving different age groups, occurred in rural areas of the Chabahar district in southeast Iran. These outbreaks raised questions regarding the effectiveness of immunization programs in these areas. To determine the most important factors leading to these outbreaks, and to determine the effectiveness of the measles vaccination program, the present study analyzed surveillance data and performed a case-control study. The total number of reported cases during the study period was 126. The estimated vaccine effectiveness, based on the adjusted odds ratio of the case-control study, was 74.2% (95% CI, 10.2-92.6). On two occasions, both primary and secondary cases of the outbreaks were vaccinated school children. In total, 42% of all cases were aged above 7 years, and 6.3% were above 20 years. With regard to the important role of schools as the foci of contact between uninfected and infected children, supplementary immunization of children before starting in school could be effective in preventing measles outbreaks. In addition, implementation of supplementary immunization every 5-10 years in older age groups might be effective in preventing future outbreaks.     

EPI vaccines-induced antibody prevalence in 8-9 year-olds in The Gambia

OBJECTIVES: We evaluated antibody prevalence to measles, polio 1 and 3, and tetanus toxoid antibodies in 8-9 year-old children in The Gambia within the framework of the Gambia Hepatitis Intervention Study (GHIS), a large vaccine trial aimed at evaluating vaccine efficacy against hepatitis B virus (HBV) infection, chronic carriage and primary liver cancer in a high risk population. The results of the present survey were compared with a previous survey performed with the same objectives and same methodology but in different children at 3-4 years of age. METHODS: Four clusters of 200 children each were sampled as representative of the whole country. Children would have received BCG, diphtheria-pertussis-tetanus vaccine (DPT), poliovirus vaccine (OPV), measles and yellow fever immunization. The measles haemoagglutination inhibition test (HAI) was used to detect measles antibody. Antibodies to polioviruses 1 and 3 were tested using the standard polio neutralization assay described in the EPI manual (WHO 1990). An enzyme-linked immuno-sorbent assay (ELISA) was used to measure tetanus toxoid antibodies. RESULTS: A high proportion of children were fully vaccinated in both age groups. Measles antibody concentrations were < or =1 : 8 in 8.2% of 8-9 year-old vaccinated children. In the previous survey of 3-4 year-old children this was 11.3%. In the present survey, GMC was lower than in the 3-4 year-old children; 88% of 3-4 year-olds and 89% of 8-9 year-olds had detectable antibody levels against poliovirus type 1. Fewer children at 8-9 years of age had antibodies against poliovirus type 3 than 3-4 year-olds (78%vs. 89% P < 0.001). A significant overall lower proportion of 8-9 year-old children had detectable tetanus toxoid antibodies compared to 3-4 year-old children (87%vs. 95% P < 0.001), as well as those who received four doses of DPT (90%vs. 97% P < 0.001). Conclusions High vaccine coverage is achieved in The Gambia with EPI. With time the number of vaccinated children who are not protected against measles, poliovirus 3 and tetanus increases. Besides the maintenance of high vaccine coverage in infants and young children, booster doses of some of the EPI vaccines in adolescents should be considered.     

Vaccination levels associated with lack of measles transmission among preschool-aged populations in the United States, 1989-1991

Knowledge of the minimum level of vaccination capable of preventing measles transmission in an age group is helpful for establishing program targets for measles elimination. In 1990, during the measles resurgence in the United States, one-half of cases occurred in children aged <5 years. Although estimated population immunity among persons >or=6 years of age was 93%, immunity was lower and varied widely among preschool-aged children. To examine the association of vaccine coverage at 2 years of age and measles incidence among preschool-aged children, we analyzed ecological studies of measles incidence in Milwaukee (Wisconsin) census tracts, Dallas (Texas) ZIP code areas, and selected cities during the 1989-1991 measles resurgence. In each study area, measles incidence decreased rapidly with increasing measles vaccine coverage and became low or negligible when coverage was >or=80%. Regression analysis also suggested that measles would not be transmitted when vaccine coverage was at least 79%. A minimum vaccine coverage of approximately 80% at the second birthday in census tracts, ZIP code areas, and cities in the United States may be sufficient to prevent measles transmission among preschool-aged children if population immunity is >or=93% among persons >or=6 years of age.     

Successful control and impending elimination of measles in the Islamic Republic of Iran

Measles is still one of the most common infectious killers of children in the world, especially in developing countries. In Iran, during the prevaccine era, 150,000-500,000 cases of measles were reported annually, with a death rate of 10%-15%. After the establishment of Expanded Program on Immunization program in 1984, vaccination rates for the first and second doses of measles vaccine increased to >90% by the mid-1990s, and the number of measles cases decreased to 2652 in 1996. In response to increased numbers of cases in older age groups during 1996-2002, a nationwide measles-rubella vaccination campaign was conducted in 2003, and 33,100,000 persons (99%) aged 5-25 years were vaccinated. During 2004-2009, 221 laboratory-confirmed measles cases (<1 case per million population) were detected, primarily in rural areas and among migrant groups who traveled to or came from high-incidence countries. High routine immunization coverage, low disease incidence, and surveillance system data suggest that interruption of endemic virus transmission might have already been achieved in Iran, but challenges remain and continued efforts are needed to sustain this accomplishment.     

Rubella immunity and morbidity: effects of vaccination in Finland

The occurrence of rubella antibodies and frequency of virologically proven rubella infections in different age groups were analyzed in a large serum material (about 60,000 sera) collected both before and after the start of nationwide vaccination of children against measles, mumps and rubella in Finland in 1982. The combined live vaccine significantly raised the rubella immunity of children and shifted rubella infections to older ages. In 1986, 91-98% immunity was found in the 2-10-year-old children so far covered by the vaccination programme; no rubella cases were diagnosed in this age group. We also demonstrated that another rubella vaccine given to about 60% of 13-year-old girls since 1975 both raised the immunity and reduced the occurrence of rubella in the vaccinated population. It is concluded that the rubella vaccinations, especially the combined vaccine given to small children, are effective, although the total number of reported rubella cases in the whole population did not decrease significantly during the study period.     

Approach to verify the status of measles, rubella, and congenital rubella syndrome elimination in Costa Rica

Costa Rica introduced the measles-mumps-rubella (MMR) vaccine in 1986. The Ministry of Health adopted the goal of eliminating endemic measles in 1991 by achieving and maintaining high vaccine coverage through routine delivery, mass campaigns and outreach activities, and the strengthening of expanded program on immunization (EPI) surveillance. Measles and rubella immunization strategies shifted susceptibility to older age groups, leading to the introduction of MMR2 in 1992, administered at age 7 years. In 2000, the goal of accelerated rubella control and congenital rubella syndrome prevention was established, and a nationwide vaccination campaign targeting men and women aged 15-39 was implemented to immunize the population of reproductive age. The last endemic case of measles was confirmed in 1999, and at the end of 2001 Costa Rica reported the last endemic cases of rubella and congenital rubella syndrome. Imported cases of measles and rubella were detected in 2003 and 2005, with no secondary cases detected. In 2008, Costa Rica established a National Committee of Experts, supported by technical teams, to collect the evidence required to verify the interruption of endemic transmission of the measles and rubella viruses. The evidence includes information on trends and epidemiologic analysis, molecular epidemiology, population immunity, the quality of surveillance, and the sustainability of the EPI program.     

Elimination of hepatocellular carcinoma and acute hepatitis B in children 25 years after a hepatitis B newborn and catch-up immunization program

Alaska Native people experience the highest rates of acute and chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) in the United States. We examined the effect of a universal newborn immunization with hepatitis B vaccine and mass population screening immunization program initiated in 1984 on rates of HBV and HCC in children 25 years later. During this time, the population of Alaska Native people grew from an estimated 75,000 to 130,000 persons. A surveillance system to detect acute HBV infection in Alaska Native facilities was established in 1981. Cases of HCC in children under 20 years of age were identified using a National Cancer Institute (NCI)-funded Cancer Registry established in 1969 coupled with an active surveillance program of screening persons with chronic HBV semiannually for alpha-fetoprotein since 1982. The incidence of acute symptomatic HBV infection in persons <20 years of age fell from cases 19/100,000 in 1981-1982 to 0/100,000 in 1993-1994. No cases of acute HBV have occurred in children since 1992. The incidence of HCC in persons <20 years decreased from 3/100,000 in 1984-1988 to zero in 1995-1999 and no cases have occurred since 1999. The number of identified hepatitis B surface antigen-positive children <20 years in the Alaska Native population declined from 657 in 1987 to two in 2008. Conclusion: Universal newborn vaccination coupled with mass screening and immunization of susceptible Alaska Natives has eliminated HCC and acute symptomatic HBV infection among Alaska Native children and this approach is the best way to prevent HBV-related disease in children.     

Short report: assessing field vaccine efficacy for measles in famine-affected rural Ethiopia

Measles is a major cause of mortality in complex emergencies. Both high vaccination coverage and vaccine efficacy are required to prevent major epidemics of measles in such situations. Evaluation of field vaccine efficacy is a critical but underutilized component of program monitoring in emergencies, and is particularly important in rural areas where the integrity of the cold chain is difficult to guarantee. In July 2000, we evaluated the field vaccine efficacy for measles vaccination by comparing the incidence of cases in vaccinated and unvaccinated groups during a two-stage cluster survey of 563 children in Ethiopia. Approximately 30% of the measles cases occurred in vaccinated children. Estimated field vaccine efficacy for measles was 66.9% in children 9-36 months old. The finding of a field vaccine efficacy for measles less than 80% warrants formal assessment of measles vaccine efficacy, particularly in famine emergencies where measles is associated with a high case fatality rate.     

Efficacy of measles and rubella vaccination one year after the nationwide campaign in Shiraz, Iran.

BACKGROUND: The World Health Organization target for measles elimination in the Eastern Mediterranean Region was established in 2010. In Iran, the national measles-rubella campaign, targeting individuals aged 5-25 years, was initiated in December 2003. METHODS: To evaluate the impact of the campaign after one year, 909 serum samples were collected in Shiraz, southern Iran, from a population aged 6-26 years, divided into five groups according to age. IgG antibodies were tested using ELISA for the measles and rubella antibodies, and the plaque reduction neutralization test (PRNT; measles) was used for samples with equivocal results. RESULTS: Measles protective immunity reached 80.6%, 72.7%, 84.9%, and 87.5% and rubella immunity reached 91.0%, 99.6%, 99.6%, and 97.0% for the age groups 6-10, 11-15, 16-20, and 20-26 years, respectively. Seropositivity to the rubella virus in this population was high, especially in women of childbearing age (98.9%), thereby preventing congenital rubella infections. However for measles, it was significantly lower than the rate required to achieve >or=95% coverage for elimination. CONCLUSIONS: These data indicate that an increase in immunization coverage by supplementary administration of a second dose of measles vaccine is needed to interrupt the endemic transmission of the measles virus.     

Measles vaccination coverage during poliomyelitis national immunization days in Burkina Faso, 1999

In 1999, Burkina Faso added measles vaccine during the second round of its poliomyelitis national immunization days (NIDs). A cluster survey was conducted in each of the country's 53 health districts to assess vaccination coverage achieved by the campaign. Forty-four percent of children aged 9-59 months had a documented prior measles vaccination, and 88% were vaccinated during NIDs. Eighty-five percent of children not previously vaccinated received measles vaccine during the campaign. Although routine vaccination coverage varied substantially among children from various socioeconomic groups, the campaign appeared to almost equally reach all groups of children surveyed. Poliovirus vaccine coverage was 90% when measles vaccine was added to the campaign, compared with 88% during the first round. In Burkina Faso, the addition of measles vaccine to poliomyelitis NIDs achieved greater equity in measles vaccination coverage according to a number of socioeconomic factors without compromising the coverage of poliovirus vaccination.     

Immunogenicity of standard-titer measles vaccine in HIV-1-infected and uninfected Zambian children: an observational study

BACKGROUND: Achieving the level of population immunity required for measles elimination may be difficult in regions of high human immunodeficiency virus type 1 (HIV-1) prevalence, because HIV-1-infected children may be less likely to respond to or maintain protective antibody levels after vaccination. METHODS: We conducted a prospective study of the immunogenicity of standard-titer measles vaccine administered at 9 months of age to HIV-1-infected and uninfected children in Lusaka, Zambia. RESULTS: From May 2000 to November 2002, 696 children aged 2-8 months were enrolled. Within 6 months of vaccination, 88% of 50 HIV-1-infected children developed antibody levels of >or=120 mIU/mL, compared with 94% of 98 HIV-seronegative children and 94% of 211 HIV-seropositive but uninfected children (P=.3). By 27 months after vaccination, however, only half of the 18 HIV-1-infected children who survived and returned for follow-up maintained measles antibody levels >or=120 mIU/mL, compared with 89% of 71 uninfected children (P=.001) and in contrast with 92% of 12 HIV-1-infected children revaccinated during a supplemental measles immunization activity. CONCLUSIONS: Although HIV-1-infected children showed good primary antibody responses to measles vaccine, their rapid waning of antibody suggests that measles vaccination campaigns may need to be repeated more frequently in areas of high HIV-1 prevalence.     

Measles vaccine coverage and immune response in children of Caiabi and Metuktire Indian tribes living in malarial endemic area: Parque indígena do Xingu, Central Brazil.

Measles vaccination efficiency was evaluated in children from two Indian tribes - Caiabi and Metuktire - living in the Amazon region, in the Parque Indigena do Xingu (PIX).The population sample, selected at random, made up 37 Caiabi and 28 Metuktire children, aged from 20-75 months (40%). For operational and epidemiological reasons, measles vaccine is given from 6 months of age.The average age of children when they received the vaccine was 11.5 months for the first dose and 20 months for the second.The search for IgG antibodies against measles virus and Plasmodium falciparum was made through immunofluorescence assay (IFA). Measles vaccine coverage has reached 60% at 12 months of age and 92% at 18 months, whereas post-vaccine serum conversion was 95% in Caiabi children (geometric mean of titres (GMT) 126) and 89% in Metuktire (GMT 109).The difference in GMT is not statistically significant. Seventy-three per cent of Caiabi children (GMT 101) and 100% of Metuktire children (GMT135) were plasmodium antibody positive, showing they had been exposed to malarial infection. Despite the differences detected, the immune response to measles vaccine was satisfactory in both groups, with a positive percentage consistent with that achieved in non-malarial areas in Americas.The results show the efficiency of a vaccination programme in an indigenous area despite the difficulties in reaching the villages and maintaining the cold chain, and also despite the malaria endemicity.     

Prospects for the eradication of infectious diseases

The meaning of eradication, which is an irreversible conclusion, is considered primarily to distinguish it from elimination, which is reversible from outside the area. Poliomyelitis and measles are at present the diseases for which conditions most favor an attempt to produce eradication. Poliomyelitis has now reached a frequency in the developing world as high as it was in the prevaccine era of the United States. The use of oral vaccine is a deliberate attempt to substitute the wild-type polioviruses in the community with the vaccine-like viruses derived from the vaccine itself. Mass use of vaccine in all children less than five years of age on a single day twice in a year has produced a critical decrease in the incidence of the disease in Brazil. Following determined efforts to achieve immunization of at least 95% of the population, the United States is now nearing the state of complete freedom from the transmission of measles virus. The use of diploid cells for making vaccine has enabled the virus to be given as an aerosol to babies less than six months of age and would be of particular value in developing countries. The high transmissibility of measles makes a severe demand for vaccine, but so long as the uptake of vaccine reaches at least 90%, the successful elimination of measles is extremely probable.     

2008年新疆维吾尔自治区实施麻疹疫苗后续强化免疫活动评价

目的探讨加速控制和消除麻疹的策略和措施。方法 2008年对新疆维吾尔自治区全区范围8月龄～6岁儿童实施了麻疹疫苗（MV）后续免疫活动;利用新疆维吾尔自治区统计局资料、疫苗分发数、疫情资料等,对报告接种情况进行了评价。结果全疆麻疹强化免疫应种儿童1641861人,实际免疫儿童1616117人,接种率为98.99%,以县为单位报告接种率95%以上。结论开展MV初始强化免疫和后续强化免疫对控制麻疹效果非常显著。     

Epidemic measles in a highly immunized rural West African (Gambian) village

A measles epidemic occurred in a rural West African village, despite documented immunization in 90% of the less than 10-year age group. In contrast to previous epidemics, this outbreak caused no associated deaths among the 54 cases diagnosed. Immunization protected against infection--only 3.6% of immunized children developed measles, whereas 30.1% of those not immunized became ill (P less than .001). Thus, the vaccine efficacy rate was 90.1%. The average age at presentation was 72 months, and older patients were more likely to have severe disease. Nutritional status had no effect on susceptibility to measles infection or on outcome; weight loss (350 +/- 170 g) was most marked during the prodromal phase in young children. Infection was more severe when more than one case was diagnosed in a household (P less than .05) and in conditions of overcrowding, which were also associated with higher infection rates (P less than .02). Although immunization did not stop the spread of the epidemic within the village, a strict quarantine in the medical clinic probably prevented spread to other villages.     

Estimate of the cost/benefit ratio of measles vaccination

Among primary health care programs, one of those that has the highest benefit/cost ratio is measles immunization. An estimate of cases, complicated cases and deaths that could have occurred if such immunization program would not have been run, and costs of medical care (hospitalization, physician's visits, medical treatment and rehabilitation), were calculated. Since population at risk has a steady-state given by those who enter -births- and releave it -when they are 15 years old-, if the program did not exist more than 2 million cases and at least 60,000 deaths from measles would have occurred annually. This hypothetical situation is compared with the actual situation of measles in Mexico during the 80's; 1) no more than 100,000 cases could have been estimated to occur in the very extreme case of notifying only one out of 10 cases. 2) The proportions of vaccinated and immune children under five reach 70 percent; this situation has produced 3) a fade out of epidemicity and has increased the critical size of community population for epidemics and doubled the interepidemic interval with the corollary of 4) increasing the average age of infection. The average cost of vaccinating a child was estimated near 1.25 dollars (US). Estimated costs of disease are related to individual losses. Taking into account these factors, benefit/cost ratio of measles immunization in Mexico is, at least, 100:1. Measles transmission patterns in Mexico are discussed since they lead to increase the benefit/cost ratio as compared to countries where the age of infection was put up before the immunization era. To expand investments on measles immunization is recommended.     

Thailand Expanded Program on Immunization: a ten-years review of coverage and impact on EPI target diseases

The national immunization coverage in Thailand for all types of vaccine has been steadily increasing since 1978, when the EPI was formally launched. The coverage in 1987 was 96% for BCG, 75% for DPT, 74% for OPV, and 60% for TT. Measles vaccine, which started only in late 1984, had the lowest coverage, 51%, in 1987. During the period 1982-1987, the drop-out rates between the first and third dose of DPT and OPV decreased dramatically from 69% to 13% and from 42% to 13% respectively. Sampling surveys of immunization coverage showed higher coverage for DPT and OPV than those from reporting in all regions, especially in the capital city which has a high concentration of the private health sector. Only the northeastern region had less coverage from surveys than from reporting. Following the launch of EPI, the disease incidence demonstrated a clearly downward trend for diphtheria, poliomyelitis, and measles, while in the case of pertussis and neonatal tetanus, slower of still fluctuating declines were observed. The reported age-specific incidences per 100,000 population in 1986 for children 0-4 years were as follows: 4 for diphtheria, 0.9 for poliomyelities, 180 for measles, 14 for pertussis, and 10 for tetanus.     

南京某单位新入职人员麻疹抗体现状调查

目的通过了解南京某单位新入职人员麻疹血清抗体情况,为制定免疫策略提供依据。方法采用ELISA检测南京某单位新入职人员麻疹Ig G抗体情况。结果共采样调查546人,年龄17~24岁,麻疹抗体阳性率为98.4%,抗体几何平均滴度(geometric mean titer,GMT)为1662 m IU/ml,抗体阳性率和GMT在各年龄段人群间两两比较差异无统计学意义(P均0.05);有麻疹疫苗接种史人群的麻疹抗体阳性率和GMT高于无接种史或接种史不详人群(P均0.05);不同地区及有无麻疹病史人群麻疹抗体阳性率之间差异无统计学意义(P均0.05)。结论该单位新入职人员麻疹血清抗体水平和阳性率较高,已基本形成了预防麻疹的免疫屏障。     

Toward measles elimination in Bahrain--a Middle East country experience

Measles was a leading cause of infant and child morbidity and mortality in Bahrain before the introduction of measles vaccine in 1974. With the establishment of the Expanded Program on Immunization (EPI) in 1981 and the introduction of a second dose of measles vaccine in 1985, coverage for first and second doses of measles vaccine increased to 94% by 1997 and has been sustained >97% since 2001. Measles, mumps, and rubella (MMR) immunization campaigns targeting 12-year-old students were conducted annually during 1998-2006 and achieved coverage of >95%. As a result, the incidence of measles in Bahrain has declined markedly over the past 4 decades, to 2.7 cases per million persons in 2009. Recent confirmed measles cases have occurred sporadically, in undervaccinated children or in infants too young or adults too old to receive measles vaccine. Bahrain has made significant progress toward measles elimination by sustaining high immunization coverage and strengthening case-based measles surveillance activities. Further success will depend on improved identification and immunization of undervaccinated expatriate workers and their families.