The protective effect of measles vaccine under routine vaccination conditions in Dar es Salaam, Tanzania: a case-control study

A case-control study was conducted to determine the protective effect of measles vaccine under routine vaccination conditions in Dar es Salaam, Tanzania. A total of 172 cases of measles were obtained over two six-week periods from hospitals likely to admit such cases in the city and their mothers interviewed using a questionnaire that had been developed for the purpose. In addition, each case was matched to four controls for age, sex and place of residence and their mothers were also interviewed using the same questionnaire as for the cases. Vaccination status of the cases and the controls was ascertained by asking the mothers as well as obtaining vaccination information from the Mother-and-Child or Road-to-Health (MCH) clinic cards normally issued to mothers at first vaccination of their children. The overall protective effect of measles vaccine in all age groups studied was found to be 54% (95% confidence limits (CL)36%-67%) when mothers' recall for vaccination status was used. This level of protection was considered to be low compared with the efficacy of the vaccine under experimental conditions in controlled trials previously reported. However when MCH Clinic cards were used to ascertain vaccination status the protective effect rose to as high as 96% (95% CL 83%-99%). Potential biases in the study design and their role in masking or exaggerating the vaccine efficacy are discussed. It was therefore concluded that the protective effect of measles vaccine under routine vaccination conditions prevailing in Dar es Salaam region at the time of this study was as high as observed under experimental conditions when ascertainment of vaccination status was record-based. The study therefore recommended that, whenever in doubt about vaccine efficacy, simple study designs like the case-control method should be used to quickly evaluate vaccine efficacy by utilizing record-based vaccination status ascertainment methods.     

Evaluation of the effectiveness of BCG vaccination using the case-control method in Buenos Aires, Argentina

A retrospective case-control study was conducted in Argentina to determine the protection conferred by BCG vaccination against tuberculosis in children under six years of age, in an area where coverage is about 55%. A total of 175 tuberculosis patients were included. Five controls selected from patients treated at the same hospital as those under study for reasons other than tuberculosis were matched to each case on the basis of age, socioeconomic origin, nutritional status and place of residence. Information on BCG vaccination status was collected by an independent examiner. Tuberculosis localizations were as follows: 152 pulmonary, pleural and/or miliary; 18 meningitis; 2 lymphadenitis; 2 osteoarticular; and 1 otic. The diagnosis was based on bacteriological and histopathological tests, computerized tomography, radiology, clinical examination, endoscopy, and proved source of infection. The protective effect of BCG among those who were vaccinated was 73.0% with 95% confidence limits of 82% and 62%. According to these results BCG vaccination given early in life is very effective in preventing tuberculosis.     

Investigation of the effectiveness of measles vaccination in children in Kenya

Laboratory studies were performed on 128 children clinically diagnosed as measles when seen at the Infectious Diseases Hospital, Kenyatta National Hospital (IDH), Nairobi (86 cases) and the Rural Health Training Centre, Maragua, Central Province (42 cases) between 9 July and 31 August 1984. A concurrent measles infection was confirmed in 95% of the children seen at IDH and in 85% of those seen at Maragua, with similar proportions of confirmations in children who had, and who had not, received measles vaccine. No differences in the number of sero-conversions nor in the absolute levels of acute or convalescent HI antibody titres could be detected between vaccinated and unvaccinated children. Analysis of the cases seen at Maragua indicates that about two thirds of the children who had received vaccine were protected. A pilot study of vaccinating children at 8 months and again at 12-13 months is suggested in an attempt to eradicate measles.     

A case-control study to evaluate the effectiveness of mass neonatal BCG vaccination among Canadian Indians

This paper reports a case-control study to assess the protective effect of BCG (bacille Calmette-Guérin) vaccination among Indian infants in Manitoba, Canada. A record of past BCG vaccination was found in 49 per cent of the tuberculosis cases, compared to 77 per cent of the controls, yielding a relative risk of 0.30. Stratified analysis, controlling for age, increased the relative risk to 0.39 (95% confidence interval 0.22 - 0.69). The preventive fraction was 44 per cent. Non-differential misclassification of exposure status could have occurred; if this was adjusted for, the relative risk would be reduced. If only bacteriologically confirmed cases were analyzed, the age-adjusted relative risk was 0.27. The protective effect of BCG vaccination in the newborn among Manitoba Indians is therefore at least 60 per cent. The implications for health policy in this population are further discussed.     

The effectiveness of maternal pertussis vaccination in protecting newborn infants in Brazil: A case-control study

IntroductionIn 2014, the Brazilian Ministry of Health (MoH) recommended Tdap to pregnant women in response to a significant increase in the incidence of pertussis among infants. The present study assessed the effectiveness of maternal immunization in preventing pertussis in infants.MethodsAn unmatched case-control study was undertaken in São Paulo State, Brazil from February 2015 to July 2016. Cases were infants aged <8 weeks at onset of pertussis reported to the Surveillance System and confirmed by real-time polymerase chain reaction or culture. Four to six healthy infants were selected as controls per case from birth certificates in the Information System on Live Births database. General characteristics and mother’s vaccination status were compared between cases and controls. The vaccine effectiveness (VE) was calculated as 1 – odds ratio (OR). For the adjusted VE, the OR was calculated using logistic regression analysis.ResultsForty-two cases and 248 controls were enrolled in the study. Mothers of 8 cases (19.1%) and 143 controls (57.4%) were vaccinated during pregnancy, resulting in an unadjusted VE of 82.6% (95% confidence interval [CI], 60.8–92.3%). The VE was unchanged after adjusting for maternal age and monthly household income.ConclusionMaternal pertussis vaccination during pregnancy was effective in protecting infants aged <8 weeks from pertussis.     

Non-specific effect of measles vaccination on overall child mortality in an area of rural India with high vaccination coverage: a population-based case-control study

OBJECTIVE: To determine whether vaccination against measles in a population with sustained high vaccination coverage and relatively low child mortality reduces overall child mortality. METHODS: In April and May 2000, a population-based, case-control study was conducted at Ballabgarh (an area in rural northern India). Eligible cases were 330 children born between 1 January 1991 and 31 December 1998 who died aged 12-59 months. A programme was used to match 320 controls for age, sex, family size, and area of residence from a birth cohort of 15 578 born during the same time period. FINDINGS: The analysis used 318 matched pairs and suggested that children aged 12-59 months who did not receive measles vaccination in infancy were three times more likely to die than those vaccinated against measles. Children from lower caste households who were not vaccinated in infancy had the highest risk of mortality (odds ratio, 8.9). A 27% increase in child mortality was attributable to failure to vaccinate against measles in the study population. CONCLUSION: Measles vaccine seems to have a non-specific reducing effect on overall child mortality in this population. If true, children in lower castes may reap the greatest gains in survival. The findings should be interpreted with caution because the nutritional status of the children was not recorded and may be a residual confounder. "All-cause mortality" is a potentially useful epidemiological endpoint for future vaccine trials.     

Computers and the effectiveness of the measles vaccination campaign in England and Wales

Summary Measles vaccination on a large scale began in England and Wales in 1968. We have compared the incidence of notified measles from 1968 to 1976 in the population whose vaccination programme was computer-assisted by 1971 with that in the population where computers were not used. The measles experience of both populations was similar from 1968 to 1970. Thereafter, all the incidence rates fell, the decline being most marked in the computer population. For the period 1971–6, the difference between the rates for the two populations is statistically significant, and the difference persists and remains significant when the urban and rural components of the populations are examined separately. We conclude that computers contributed to the lower incidence of measles in the computer population between 1971 and 1976 and suggest that the severity of measles epidemics may be further reduced by the nationwide use of computers.     

Evaluation of vaccination policies. The case of measles

Any immunization policy involves a given vaccination coverage rate and a related cost of implementation. Moreover, for each vaccination coverage rate, there are associated costs for treating residual morbidity and its human and social consequences. Thus, an overall cost can be determined for each coverage rate, and an optimal policy can be defined. This approach is illustrated in the paper by examining the costs and advantages of a measles vaccination program for France. We first calculate the various costs of the present situation (in which vaccination coverage is close to 0%), and then simulate the cost of total eradication of measles (vaccination coverage = 100%). The results show that the latter policy is to be preferred from every point of view.     

Evaluation of an early two-dose measles vaccination schedule.

Vaccination at 6 months of age followed by routine revaccination is recommended when exposure of infants to measles is likely. Dade County, Florida, began this early two-dose schedule during a large epidemic in 1986-1987 (i.e., 22% of cases occurred in infants aged 6-11 months). This schedule was continued routinely in high-risk areas. The effect of an early two-dose schedule on measles prevention in the county was examined by comparing measles vaccination coverage and epidemiology before (1985-1987) and after (1988-1996) the schedule became routine. To assess serologic response, seroprevalence of measles antibody among children aged 4-6 years in 1995 was examined. To evaluate vaccine effectiveness, a case-control study was conducted among preschool-aged children. Among those aged 2 years, vaccination coverage with > or =1 dose increased from 75% to 94% in 1996. The number of annual cases declined, and endemic measles transmission reportedly ended after 1993. Seroprevalence of plaque reduction neutralization antibody (titer > 1:120) among those receiving vaccination according to an early two-dose schedule and a single dose at age > or =12 months was 94% (95% confidence interval: 89, 98) and 98% (95% confidence interval: 95, 100). In these groups, vaccine effectiveness was comparably high. Early two-dose measles vaccination is associated with improved coverage and a comparably high level of humoral immunity and clinical protection as a single dose at age > or =12 months. This strategy can be useful in areas at high risk for measles among infants.     

Mumps, measles and rubella vaccination: a pragmatic study

The acceptability, adverse effects and uptake of MMR vaccine were assessed in an open pragmatic study. 96.5% of parents chose vaccination with MMR rather than monocomponent measles. Few parents could correctly name a complication of mumps (40.4%), measles (21.7%) or rubella (25.3%). In the three weeks following vaccination, 15.9% of infants had local reactions, 26.4% had rashes, and 30.3% fever. There was no increase in uptake of measles vaccination during the study, but it led to improvements in programme organisation which subsequently boosted coverage.     

Single-dose varicella vaccine effectiveness in Brazil: A case-control study

BackgroundVaricella vaccine was introduced into the Brazilian Immunization Program in October 2013, as a single-dose schedule administered at 15 months of age. Its effectiveness had not yet been assessed in the country.MethodsA matched case-control study was carried out in São Paulo and Goiânia (Southeast and Midwest regions, respectively), Brazil. Suspected cases, were identified through a prospective surveillance established in the study sites. All cases had specimens from skin lesion collected for molecular laboratory testing. Cases were confirmed by either clinical or PCR of skin lesions and classified as mild, moderate, and severe disease.Two neighborhood controls were selected for each case. Cases and controls were aged 15–32 months and interviewed at home. Evidence of prior vaccination was obtained from vaccination cards. Univariate and multivariate logistic regression models were used, and odds ratio and its respective 95% confidence intervals were estimated. Vaccine effectiveness was estimated by comparing de odds of having received varicella vaccine among cases and controls.ResultsA total of 168 cases and 301 controls were enrolled. Moderate and severe illness, was found in 33.3% and 9.9% of the cases. Effectiveness of a single dose varicella vaccine was 86% (95%CI 72–92%) against disease of any severity and 93% (95%CI 82–97%) against moderate and severe disease. Out of 168 cases, 81.8% had positive PCR results for wild-type strains, and 22.0% were breakthrough varicella cases. Breakthrough cases were milder compared to non-breakthrough cases (p < .001).ConclusionsEffectiveness of single dose varicella vaccine in Brazil is comparable to that in other countries where breakthrough varicella cases have also been found to occur. The goal of the varicella vaccination program, along with disease burden and affordability should be taken into consideration when considering the adoption of a second dose of varicella vaccine into national immunization programs.     

Scar size and effectiveness of Bacillus Calmette Guerin (BCG) vaccination in the prevention of tuberculosis and leprosy: a case-control study

BACKGROUND: The study was undertaken to estimate the effectiveness of BCG vaccination in relation to scar size in the prevention of tuberculosis and leprosy. METHODS: The present study was designed as hospital-based pair-matched case-control study and was carried out at Government Medical College Hospital, Nagpur, Maharashtra, India. It included 877 cases of tuberculosis and 292 cases of leprosy (diagnosed by WHO criteria), born onwards 1962. Each case was pair-matched with one control for age, sex and socio-economic status. BCG vaccination status was assessed by examination for the presence of BCG scar, immunisation records if available and information from subjects/parents of children. Subjects uncertain about BCG vaccination were not included. The diameter of the BCG scar was measured both across and along the arm in millimeters using a plastic ruler. The average was then calculated. RESULTS: A significant protective association between BCG vaccination and tuberculosis (OR=0.38, 95% CI 0.31-0.47) and leprosy (OR = 0.38, 95% CI 0.26-0.55) was observed. The overall vaccine effectiveness (VE) was 62% (95% CI 53-69) against tuberculosis and 62% (95% CI 45- against leprosy. Vaccine effectiveness against tuberculosis and leprosy was non-significantly greater in the group who had BCG scar size < or =5 mm as compared to subjects who had BCG scar size > 5 mm. Thus there was no clear association between BCG scar size and its effectiveness. CONCLUSION: The current study did not identify any significant association between BCG scar size and its effectiveness against tuberculosis or leprosy.     

Effectiveness of maternal pertussis vaccination in Singapore: A test-negative case-control study

Pertussis vaccination (Tdap -Tetanus-diphtheria-acellular pertussis) for pregnant women has been recommended since November 2017 in Singapore. In this prospective test-negative case-control study from 2018 to 2019, we aimed to evaluate vaccine effectiveness (VE) against pertussis infection and pertussis-related intensive care unit (ICU) admission according to Tdap (Tetanus-diphtheria-acellular pertussis) during pregnancy and/or infant pertussis vaccination. A total of 58 children (26 cases, 32 controls) were recruited with 4 ICU admissions. The median age was 3 months (interquartile range [IQR] 1.50–4.56 months). Overall, 25.9 % of mothers had received antenatal Tdap vaccination and 43.1 % of infants received pertussis vaccination, majority only 1 dose. Tdap in pregnancy alone without infant vaccine or with 0–1 infant dose had a VE of 97.62 % (95 % confidence interval [CI] 53.25–99.88 %), 98.17 % (95 %CI 66.61–99.9 %) respectively, against pertussis infection and 71.9 % (95 %CI 0.0–98.64), 75.86 % (95 % CI 0.0–98.78) respectively, against ICU admissions. Conclusion: Maternal Tdap vaccination was highly protective against infant pertussis and should be routinely recommended for all pregnant women.     

The effect of time since measles vaccination and age at first dose on measles vaccine effectiveness – A systematic review

BackgroundIn settings where measles has been eliminated, vaccine-derived immunity may in theory wane more rapidly due to a lack of immune boosting by circulating measles virus. We aimed to assess whether measles vaccine effectiveness (VE) waned over time, and if so, whether differentially in measles-eliminated and measles-endemic settings.MethodsWe performed a systematic literature review of studies that reported VE and time since vaccination with measles-containing vaccine (MCV). We extracted information on case definition (clinical symptoms and/or laboratory diagnosis), method of vaccination status ascertainment (medical record or vaccine registry), as well as any biases which may have arisen from cold chain issues and a lack of an age at first dose of MCV. We then used linear regression to evaluate VE as a function of age at first dose of MCV and time since MCV.ResultsAfter screening 14,782 citations, we identified three full-text articles from measles-eliminated settings and 33 articles from measles-endemic settings. In elimination settings, two-dose VE estimates increased as age at first dose of MCV increased and decreased as time since MCV increased; however, the small number of studies available limited interpretation. In measles-endemic settings, one-dose VE increased by 1.5% (95% CI 0.5, 2.5) for every month increase in age at first dose of MCV. We found no evidence of waning VE in endemic settings.ConclusionsThe paucity of data from measles-eliminated settings indicates that additional studies and approaches (such as studies using proxies including laboratory correlates of protection) are needed to answer the question of whether VE in measles-eliminated settings wanes. Age at first dose of MCV was the most important factor in determining VE. More VE studies need to be conducted in elimination settings, and standards should be developed for information collected and reported in such studies.     

南阳市卧龙区麻疹常规免疫与普种防制效果分析

为控制麻疹疫情 ,切实提高免疫效果 ,我们自1986年开始积极创造条件 ,在原南阳市城区和近郊三乡农村设立固定接种点 ,配备冷藏和冷链运转设备 ,规范冷链运转和接种程序 ,1994年南阳市撤地设市建区以后 ,又在所辖的 11个乡镇推广应用门诊集中化接种 ,对满 8月龄至 10岁儿童实施普种 ,现将防制效果分析如下。1　资料与方法1.1　麻疹疫苗免疫接种的组织实施1.1.1　接种网点　城区实施门诊集中接种 ,农村实行以村为单位分散式接种 ,即农村以村为单位 ,每村设一个接种点。 1994年以后在全区范围内实施门诊集中接种。1.1.2　冷藏、冷链运转接种设…     

Evaluation of the effectiveness of large-scale vaccination against influenza in the USSR

Vaccination is at present the only means of influenza control; so far, large-scale trials of live vaccine have been made mainly in the USSR. This paper discusses such a trial in persons above 12 years of age.     

深圳市成人麻疹发病影响因素的病例对照研究

目的探讨深圳市成人麻疹发病的影响因素,为制定麻疹防控策略提供依据。方法采用分层随机抽样的方法,在中国疾病预防控制信息系统中选取深圳市2008年1～3月的成人麻疹新发病例151例,根据1∶1配对的病例对照研究方法选取151名健康成人作为对照,调查研究对象的人口学资料、麻疹疫苗免疫史等信息。结果来深圳时间≥1年的成人麻疹发病低于在深圳不到1年的成人(OR=0.37,P=0.010)、发病前2周与麻疹病人有过接触的成人麻疹发病高于没有接触麻疹病例的成人(OR=9.42,P<0.001)、过去3周离开过本市的成人麻疹发病高于未离开过本市的成人(OR=4.93,P=0.003)。结论来深圳时间较短、发病前2周与麻疹病人有过接触、过去3周离开过本市是深圳市成人麻疹发病的危险因素。