Measles Outbreak investigation in a Small Hamlet in ruralfield practice area of a Medical College- Lessons learnt in thecurrent context

INTRODUCTION

Measles is one of the leading causes of death among young children though a safe and cost-effective vaccine is available to prevent the disease. In 2018 there was more than 140,000 measles death globally and predominantly among under five age group. Measles vaccination resulted in a 73% drop in measles deaths between 2000 and 2018 worldwide. More than 95% of measles deaths occur in lowincome countries with poor health infrastructure. In 2007, about 82% of the world's children received one dose of measles vaccine in their first year of birth through routine health services, up from 72% in 2000. Of the estimated 19.2 million infants not vaccinated with at least one dose of measles vaccine through routine immunization in 2018, about 6.1 million were in 3 countries: India, Nigeria and Pakistan.¹ Despite measles immunization coverage being 79% as on 1995 and a significant fall in the number of reported cases worldwide, measles continues to cause considerable illness and death in children accounting for 44 million cases and one million deaths annually.² More than 95% of measles deaths occur in low-income countries with poor health infrastructure.¹ Committed to United Nations Millennium Development goal of reducing the under-five child mortality rate by two-thirds by the year 2015, Government of India developed a Multi-Year Strategic Plan (MYSP). The strategic plan includes the goals of reducing measles mortality by 2/3rd by 2010; achieving at least 90% measles immunization coverage in 80% of the districts of the country by 2009; and collection of good quality epidemiological data through active surveillance and outbreak investigation to use them to guide further actions.³

Many cases of fever and rashes suspected to be measles were reported in first quarter of 2007 from a small hamlet under Kaiwara PHC area, which is the rural field practice area of the institution by Junior doctors during their regular field visit. The outbreak occurred in a small village with 18 households with a total population of 98, which is about four kilometers from the primary health center. Hence, the present study was conducted with the objectives of investigating the measles outbreak and assesses the various epidemiological features associated with measles and to assess the measles immunization status among the affected population.

Materials and Methods

A team of junior doctors and Health Assistants from PHC under the guidance of the faculty from Department of Community Medicine of the institution and Medical officer of the PHC were trained to collect information for investigation purpose. House-to-house survey was conducted for case search in the population and information was collected as per Vaccine Preventable Disease (VPD)–OB002 & 003 forms of Field guide, Measles Surveillance and outbreak investigation.⁽³⁾ The information was obtained from the mother or any other reliable elder person at home. Data was collected regarding socio-demographic details, immunization history, clinical history, and clinical examination of all children done to confirm clinical measles. As per measles surveillance, all the children aged below 15 years were included in the survey and followed up for a period of one month (twice the maximum incubation period) after the last case was reported.

As per standard case definition of measles surveillance³, the criteria adopted for case diagnosis of clinical measles was any child with

a. history of fever and maculopapular rash (nonvesicular or without fluid), and

b. Either with cough or coryza (running nose) or conjunctivitis (red eye).

All the affected children were followed up for any development of complications till the outbreak subside.

Ethics and informed consent: This measles outbreak investigation was undertaken as an emergency response to an outbreak as part of public health practice in line with the Measles elimination strategy as per National Programme guidelines. No investigations were done, however ethical approval was obtained from the ethical review board of the Institution. Also consent and approval was obtained from the community members to undertake the survey in the village.

Results

All the 18 houses in the hamlet were surveyed with spot map prepared. Total of 14 cases occurred amongst 32 children aged below 15 years. No cases were reported among adult population. The overall attack rate was 43.8% among children (<15 years age group). Age-specific attack rates were 33.3%, 61.5% and 31.3% in age group of 0-1, 1-6 and 6-15 years respectively (Table 1). No cases were reported among children less than nine months and above 15 years age group (Data not shown). Male: Female ratio among affected children was 2.5:1. The attack rate among males and females was 50% and 33.3% respectively, however the difference was not statistically significant (X2=0.85, P=0.358). Of the total at-risk population (<15 years), only 46.8% of them were immunized for measles (Table 2). Attack rate among unimmunized was 58.8% as compared to those among immunized which was 26.7% and the difference was not statistically significant at 5% significance level (X2=3.34, P=0.067). Among the immunized, ten cases received immunization from private sector of which four were measles affected. None of the affected children had received any Vitamin-A prophylaxis in private sector.

Vaccine efficacy (VE) was calculated using case reference method and in this study it was 54.7%. (2, 4, 5) . ARU and ARV is Attack rate among unvaccinated and Attack rate among vaccinated respectively.

(Figure 1)

Proportion of vaccine preventable cases (PVPC) was high i.e. 71.4% (10 children among 14 measles affected children did not receive any vaccination) and this could have prevented if all children were immunized at right time.

(Figure 2)

Measles-related complications were reported in four cases (28.6%) i.e. three (21.4%) had acute respiratory infections and two (14.3%) had diarrhea. No deaths were reported during the outbreak period.

Cultural practices

Measles affected children were strictly isolated at home and there was restriction of movement of the affected ones. As a customary practice, neem leaves dipped in water was used to sprinkle on the family members before they entered the house. Attitude towards disease causation was deistic and the condition was addressed to as “Amma” meaning Goddess Annamma, the local deity. Preparation and consumption of oily and nonvegetarian food was forbidden in the house. There was resistance by parents to give any form of drugs but after long persistence and counseling by the investigating team, they were convinced to let their children have vitamin-A supplements, antibiotics, and symptomatic treatment for those who had complications.

Discussion

In our study, the measles attack rate of 43.8% was high when compared to previous publications where the attack rates were less than 16.2%.^6,7,8 However, it is comparable to the results observed in a study conducted in a hamlet of Himachal Pradesh.⁹ This variation could be explained as the attack rate depends on susceptible population and immunization coverage. In our study, the high attack rate could be attributed to large susceptible population who were not immunized due to low immunization coverage. Peak attack rate in the age group of 1-6 years (ASAR=61.5%). Similar observation was noted in a study conducted in slums of Chandigarh where the peak attack rate  was 6% in the age group of 1-4 years, but in a study conducted in rural area of Shimla, the age-specific attack rate was high in 10-15 years age group (34.5%).^{6, 8} Age-specific attack rate depends on the age susceptibility and previous immunization coverage in the population. In population where immunization is still below the acceptable levels for herd immunity, measles continues to occur in younger children as observed in our study. However, in areas where the immunization coverage is good, an age-shift occurrence of measles is expected. It was observed that no child under nine months was affected in this outbreak. Review by Singh J et al has discussed that since less than 10% of the cases occur before nine months of age, this age is appropriate for routine measles immunization.¹⁰ Vaccine efficacy in our study revealed to be 54.7%. This observation is in line with a study conducted in Himachal Pradesh, where vaccine efficacy was 51% and in a study conducted in Delhi where vaccine efficacy was 62% by case reference technique which was marginally lower than the laboratory result (64.4%).^4,9 The probable reasons for the low vaccine efficacy in our study was that majority of those who were immunized had received vaccination from the private sector where cold chain maintenance is questionable and calls for due attention as this is one of the most neglected issue at the field level. Reanalysis of data from different types of studies indicates that efficacy of measles vaccine given at 9-11 months of age is of the order 85-90% in the Indian context.¹¹ Hence, it is important that measles vaccine is given at 9-11 months and more important is to maintain the cold chain properly.

Overall immunization coverage in our study was 46.8% which was much below the national average of 58.8% as per NFHS-3 report and even more less than NFHS report -4 (81.8%).¹² This low immunization coverage has been reported in similar studies conducted elsewhere in India.^{6, 9} In our study, the unimmunized population (53.2%) in the community could have formed the ground for the measles virus to establish. Therefore, there is a need to focus on improving immunization coverage especially in small hamlets where it can get neglected from routine services provided by heath care workers.

On comparing the immunization status among the measles affected and non measles affected children, attack rate among immunized was more than the attack rate among the unimmunized but was not statistically significant at 5% significance level. However, it was significant at 0.1% and this is possible due to small sample size. Thus, with increase in sample size, this might turn out to be significant at 5% level of significance. Similarly, among the measles cases, 48.8%, 32.8% and 33% of them had received vaccination in Thakur JS et al⁷ , Sharma MK et al⁸ and Bharti B and Bharti S⁹ studies, respectively.

In the present study, measles related complications were reported in 28.6% of cases and mortality was nil. While higher morbidity was reported in previous studies^6,9, it was 17.8% in Mishra et al study.^13,14 Early recognition of outbreak and proper clinical case management for post-measles complications are an important intervention to reduce the measles morbidity as well as the mortality.

In our study, the investigation was confined to the affected village and hence the results are to be viewed with this limitation of small sample size. Laboratory confirmation was not possible as the outbreak was at the peak and waning stage. Case definition restricting to “Probable cases” was adopted for operational reasons.3 The probable reasons for outbreak identified in our study are poor vaccination coverage, Low vaccine efficacy and lack of awareness among the population. Poor Vaccination coverage of 46.8% of the affected population is indicative of failure on part of the health system to immunize the susceptible population. Immunization has failed to reach these children through routine immunization. In our study, the vaccine efficacy was as low as 54.7% and since this is lower than 90% which is the expected requirement, there is a need to investigate the cold chain practice. This could probably be due to immunized children receiving vaccination from the private clinic at nearby taluk which is 12 kilometers away and not from the primary health center though it was nearer to the hamlet. This observation is indicative of the probable improper cold chain practices in the health system, more so in private sector. This also indicates the faith of the villagers in seeking healthcare more from private sector compared to public sector.⁵ Awareness regarding the need for vaccination was lacking among the mothers of this affected population which needs to be improved by awareness programmes.

Action Taken

Medical officer was intimated about the outbreak and immediate outbreak measures were taken; vitamin-A prophylaxis was given to all the affected children on convincing the parents by the investigating team. The affected children were administered antipyretics, oral rehydration salt solution and antibiotics when indicated at the house-hold level and some cases with complications were referred to the nearby hospital appropriately. The families were educated on the importance of immunization and also requested to notify any further new cases of measles in the community to the primary health center. PHC staff conducted measles immunization in nearby villages as part of outbreak control measures. As per the field guidelines for measles surveillance, the immunization was not undertaken when the outbreak was on, however mop-up immunization was subsequently, undertaken after the outbreak completely subsided.³

Recommendations

Need for increasing and sustaining high measles routine coverage i.e. over 90% is essential for achieving a suitable reduction in measles mortality. The routine immunization coverage can be strengthened by implementing regular immunization sessions at outreach sites. Specific action plan to be developed to cover such small hamlets and villages which are far away from the Primary health Centre which often get neglected for routine services. Though outbreak does not necessarily represent a failure of the immunization program, immunizing high-risk population and an adequate surveillance system in place is a priority.² Good surveillance system should ensure that all suspected measles cases are identified and notified. Case based reporting and lab confirmation of all clinically suspected measles case is essential.⁵

Creating awareness in the community is vital in improving the immunization coverage. Serological studies among vaccinated children against measles should be undertaken to explore the possibility of second dose of measles in older children as WHO recommends two doses of the vaccine to ensure immunity, as about 15% of vaccinated children fail to develop immunity from the first dose.¹

Reaching the unreached, creating awareness of child immunization, strengthening the disease surveillance and motivation of the community to utilize the existing health services needs to be further strengthened.

Conclusion

Measles outbreak continues to occur even though measles elimination strategy in place and an effective vaccine available. From the present study, it may be concluded that there is a need to strengthen routine immunization coverage by increasing the awareness level. For the vaccine to be potent and effective, maintenance of cold chain is of paramount importance not only in public sector but also in private sector.