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Indian Journal of Community Medicine

Study of Measles Incidence and Vaccination Coverage in Slums of Surat City

Author(s): VK Desai, SJ Kapadia, Pradeep Kumar, Siddharth Nirupam*

Vol. 28, No. 1 (2003-01 - 2003-03)

Deptt., of Preventive and Social Medicine, Government Medical College, Surat, India, 395001 *UNICEF, Gandhinagar, India

Keywords: Measles incidence, Urban slums, Vaccination status, Treatment-seeking behaviour, Accelerated measles control

Research question: What is the incidence of measles in slums of Surat city?

Objective: To assess the measles incidence and vaccination coverage among under five children living in the slums of Surat city.

Study-design: One-year incidence study based on parental recall, to find out the incidence of measles in under five children.

Setting: 30 slums in Surat city identified by the cluster sampling method.

Participants and sample size: 3035 under five children residing in the 30 slums identified.

Study variables: Age, sex, incidence, vaccination status, post measles complications, vaccine efficacy.

Statistical analysis: Proportions with confidence intervals and appropriate test of significance.

Results: The overall annual measles incidence rate was 7.67%. Post measles complications rate was 29.6%. The vaccination coverage in the 12-23 months age group was 49.8%. The commonest reason for non-vaccination was ignorance of parents about the seriousness of the disease and the need of vaccination.

Introduction:

Although measles has been universally known as a major child health problem and a killer of children, in developing countries like India there is paucity of measles incidence data, except for the reports on measles outbreak investigations'. While regular surveillance of measles can provide data on measles incidence, the existing situation of non-reporting of cases and non treatment seeking from medical care providers due to cultural beliefs in regard to the disease limit the scope of reliable surveillance1.

Urban slums pose a major challenge for measles control and are identified as high-risk areas leading to a high rate of measles transmission. This is because of overcrowding (giving rise to faster and wider spread of the disease) and a relatively low rate of vaccination1.The "Urban measles control initiative" was, therefore, launched in 10 cities including Surat in India in 1998 to achieve measles control through improved vaccination coverage2. This initiative envisaged a baseline incidence survey, mass measles vaccination campaign and strengthening the system of routine vaccination. Effective planning, implementation and monitoring were considered crucial for developing a pilot process of accelerated measles control in urban areas. Therefore, a baseline "measles incidence cluster survey" was undertaken to assess the magnitude of the problem.

Surat, being the second largest city in the State of Gujarat and undergoing rapid urbanization with a heavy influx of population, provided an excellent opportunity to undertake and evaluate the proposed intervention.

Among the 10 cities selected initially, Surat was the first one to undertake the baseline measles incidence survey in 1998.

Material and Methods:

The study was carried out in 30 slum clusters of Surat city selected by the cluster sampling method to study the incidence of measles in under five children. Due to inadequacy of studies on this subject, the sample size was calculated on the basis of reported vaccination coverage of 60%, in the city over a period of five years3. 40% children were thus considered susceptible and a uniform attack rate of 8% was assumed per year. The vaccinated and unvaccinated children were assumed to be evenly distributed in the study universe.

The sample size calculated at 95% level of significance with an allowable error of 12.5% was 3000 under five children and this population was to be covered in 30 clusters with a target of studying 100 children per cluster4. History of fever with rash, vaccination status, history of post measles complications and treatment seeking behaviour were also recorded by house to house survey on a pre-tested proforma, designed by UNICEF4.

The case definition used in this study was for "suspect measles" (WHO, UIP). The criteria for considering any child to have had measles were as follows:

1. Fever with rash lasting for 3 days or more and 2. Either cough/coryza (running nose) or conjunctivitis (red eyes)

The survey was carried out in May 1998 by a team comprising one doctor and health worker from the PSM department. In each cluster the first house was selected by a random number using a currency note and from that house the survey was continued till the target of 100 children under five was achieved in each cluster and information collected.

Statistical Analysis:

Data collected was analyzed in EPI INFO VERSION-6. Tests of significance wherever required were applied.

Results:

Table I: Age and sex specific incidence rates (%) of measles.

Age Group
(months)
Boys Girls Total 95% C.I.
Total
Children
Incidence
Rate
%
Total
Children
Incidence
Rate
%
Total
Children
Incidence
Rate
%
0 - 8 232 1.3 206 3.4 438 2.3 0.9 - 3.7
9 - 11 99 11.1 74 12.1 173 11.5 6.8 - 16.2
12 - 23 324 9.8 280 10.0 604 9.9 7.7 - 12.7
24 - 35 325 9.5 261 9.9 586 9.7 7.5 - 12.5
36 - 47 305 7.5 281 8.2 586 7.8 5.9 - 10.4
48 - 59 361 4.7 287 2.0 648 3.5 2.3 - 5.4
Total 1,646 7.5 1,389 7.7 3,035 7.6 6.7 - 8.6

In 30 clusters, total 3,035 children under 5 years were studied among whom 1,646 were boys and 1,389 were girls. The sex ratio was 843. The largest proportion of children (21.3%) belonged to the age group of 48-59 months.

The overall measles incidence rate in under five children was 7.67%. The mean age of case was 26.6 months - 14.2 months. The incidence rates among boys and girls were 7.5 and 7.7% respectively. The difference in incidence rate was statistically not significant (Table I).

The peak incidence of measles was in 9-11 month age group (11.5%). The 12-35 month age group contributed to about 50% of all measles cases.

Table II: Post measles complications in measles cases (n=69)

Type of Complication No. %
Diarrhoea 46 51.6
Pneumonia 35 39.3
Weight-loss, weakness 8 8.9
Total 89

Many children had more than one complications.

A period of one month after the attack of measles was taken into account for recording post measles complications. Among the 233 cases of measles, parents reported one or more post measles complications in 69 cases. Diarrhea was the commonest of all (51.6%), followed by pneumonia (39.3%). No death due to measles was reported among the surveyed population.

Table III: Treatment seeking behaviour among measles cases (n=233).

Treatment seeking behaviour No. %
Did not take Treatment 103 44.2
Treated outside home 84 36.1
Treated by home remedies 26 11.2
Details not available 20 8.6
Type of facility visited (n=84)
Private Practitioner 62 73.8
Government Hospital 8 9.5
Traditional Faith Healer 8 9.5
Minicipal Corporation Hospital 6 7.1

Out of 233 suspect measles cases, 103(44.2%) did not receive any treatment, 76(90%) were treated at public/private center and 8 cases were taken to faith healers (Table III). Only one tenth of all measles cases received vitamin A supplementation.

Table IV: Age and sex specific measles vaccination coverage rates.

Age Group
(Months)
Boys
(n=1,240)
Girls
(n=1,023)
Total
(n-2,263)
Total
Children
Coverage
Rate
%
Total
Children
Coverage
Rate
%
Total
Children
Coverage
Rate
%
9 - 11 95 33.7 65 26.1 160 30.6
12 - 23 291 52.9 249 46.2 540 49.8
24 - 35 283 52.3 227 49.8 510 51.2
36 - 47 260 48.5 246 48.4 506 48.4
48 - 59 311 48.5 236 50.4 547 49.4

334 children in whom vaccination status was unknown were not included.

An attempt was made to assess the vaccination coverage in 2,597 children (from among the 3,035 children studied) who were in the age group of 9-59 months by parental recall and by the evidence of vaccination cards.Furthermore, out of 2,597 children 334 were excluded from the analysis as their parents were uncertain about their vaccination status.

Measles vaccination coverage was 48.3% in 9-59 months age group. Vaccination coverage of boys was higher (49.3%) than girls (47.2%) but the difference was statistically not significant. The vaccination coverage in 9-11 months (which showed the highest measles incidence) was 30.6% with 33.7% in boys and 26.1% in girls.

Table V: Reasons for non-vaccination in children (9-59 months age) (n=1169).

Reason No. %
Unaware of need for vaccination 888 75.9
Myths and Misconceptions (fear of side reactions, wrong ideas about contraindications, no faith in vaccination, illness of the child) 143 12.2
Operational reasons (place and time unknown, place inaccessible, vaccinator absent, long waiting period 138 11.8

Health centres run by the Surat Municipal Corporation accounted for 65% of all vaccinations followed by government hospitals (28.5%) and private practitioners (6.5%). Of the total children vaccinated by corporation run facilities, 72.7% were vaccinated through outreach sessions. The reasons for non-vaccination have been broadly grouped into three categories (Table V). Majority of the (75.9%) children were not vaccinated due to their parent's ignorance for the need of measles vaccination. Myths and misconceptions (12.2%) and operational difficulties (11.8%) followed this.

The vaccine efficacy calculated from this study was 55%. Vaccine efficacy was estimated as the percentage reduction in disease incidence attributable to immunisation, calculated by means of the following equation1:

Vaccine efficacy (%) = ((ARU - ARI)/ARU) ×100 = (1 - RR)×100

Where:
ARU = Attack Rate among unvaccinated,
ARI = Attack Rate among immunized,
RR = ARI/ARU

Discussion:

In India, measles continues to remain a major cause of morbidity and mortality in under five children. Due to complex socio-cultural factors, passive surveillance of measles has limitations and there is no system of active surveillance of cases either.

Even after 16 years of formal introduction in the national immunisation programme, measles vaccination coverage rate lags behind that of all vaccines. Measles vaccination drop-out rates in Surat slums reported in Multi indicator cluster surveys were 19.2% (97) and 32.8% (98) respectively3. The drop-out rate for measles vaccination has been calculated as the proportion of those children who did not receive measles vaccine, out of those who received 3 doses of DPT vaccine3.

An incidence rate of 7.67% in under-five children and distribution of measles cases throughout this five-year period indicates that measles is a significant child health problem in slums of Surat City. Similar incidence studies in Vadodara, Ahmedabad, Rajkot and Jamnagar during 1999 had showed incidence rates of 4.2%, 11.4%, 10.4% and 12.0% respectively5. This further confirmed that measles is a public health problem in slums of all major cities of Gujarat State. Similar incidence rates of 6.1% and 11.8% have been reported by studies on community based measles incidence5,6. But both these studies have collected data prospectively and have not used the cluster sampling method. The 30 cluster sampling technique and retrospective data collection was used by a community based incidence study in Zimbabwe, which also revealed a very high incidence rate10. The incidence rate in 0-9 months age group in the present study was 5.5% which indicates that in slums, cases of measles do occur before the age of 9 months, (recommended age for measles vaccination). Hence no measles incidence study should exclude this age group7-9.

The very young are the most at risk and protected the least1. Mortality rates are highest in infants, especially those below 9 months of age 12 . In urban areas of the developing countries, studies1 have shown that up to a third of reported cases occur before 9 months of age when coverage is moderately high. These data have served as an impetus to develop measles vaccine, which could successfully immunize infants even before 9 months of age.

The overall vaccination coverage in the 9-59 months was 48.3%. The coverage in the 12-23 months age group was 49.8%. The compilation report of incidence studies carried out in 1999 in Ahmedabad, Rajkot and Jamnagar revealed an overall vaccination coverage between 46.7 to 58.9%. Baroda reported higher vaccination coverage (78.6%). Thus, excluding Baroda, all the cities including Surat had vaccination coverage of less than 60% in the target age group.

These studies from major cities of Gujarat reveal very valuable information that at 46.7% to 58.9% measles vaccination coverage rate, measles incidence rate were between 7.6% to 12.0% in children of slums. They also reveal that Baroda had the least incidence (4.2%) as the vaccination coverage was the highest.

The vaccine efficacy in the present study has been calculated by comparing attack ratet, between vaccinated and unvaccinated children, which is 55%. Several studies on vaccine efficacy, using the same methodology have reported figures between 59-80%10,11.

However, it is documented that vaccine efficacy for measles in 85 to 90%11-13.

The probable reasons for low vaccine efficacy observed in this study could be due to recall bias, improper cold chain maintenance or improper technique of administration.

Slums are high-risk areas leading to a high rate of disease transmission. The poor urban population groups might be an important reservoir for seeding measles virus to rural populations1. Urban slums represent a major challenge for measles control and special vaccination efforts are needed to reach this section of the population. Slums with their unique ethnic and sociological characteristics demand extra efforts to channelise information, education and communication of parents in order to achieve the desired vaccination coverage.

The present community-based incidence study is the first initiative of its kind in Surat City. Ideally an incidence study should be carried out by prospective data collection for a period of one year but it is resource intensive and time consuming. Despite the fact that the present study is based on one-year recall, there are less chances of recall bias, as an episode of fever with rash is less likely to be missed by parents. This incidence study has provided a valuable baseline data for development of the pilot process for accelerated measles control in Surat City.

The information available from this study was disseminated in order to be able to plan and implement an intervention strategy in the form of a 'mass vaccination campaign 1 for measles, which was carried out in Surat city in September 1999.

Acknowledgement:

We are thankful to UNICEF, Gandhinagar (Gujarat) for providing technical and financial support. We acknowledge the co-operation extended to us by the parents of the children in our study area.

References:

  1. WHO. Expanded Program on Immunisation, Immunological basis for measles immunization. Current WHO recommendations and future prospects, GEN/93.17.
  2. Proceedings of the national consultation meeting on urban measles control initiative, 1998, New Delhi.
  3. Reports on Multi indicator cluster surveys in slums of Surat city conducted by department of PSM, Govt. Medical College, Surat in assistance with UNICEF, Gandhinagar (Gujarat), 1996, 1997, 1998.
  4. Departmental correspondence Dr. Siddharath Nirupam, Project Officer, UNICEF. Gandhinagar, Gujarat.
  5. A compilation report on incidence studies of measles conducted in Ahmedabad, Baroda, Rajkot, Jamnagar and Surat.
  6. Dollimore N, Cutts F et al. Measles incidence, case fatality and delayed mortality in children in rural Ghana.
  7. Jain DC, Meena HS. Sero - epidemiology of measles, a three year prospective study in rural population of Rajasthan, Journal of Communicable Diseases 1990; 22(3): 165-72.
  8. Mudzamiri WS, Marufu T et al. Measles vaccine efficacy in masvingo district, Zimbabwe. Central African Journal of Medicine 1996; 42(7): 195-277.
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