| Community based Surveillance to estimate incidence and sero prevalence of acute febrile illness with focus on Dengue and Chikungunya – A prospective multi-centric cohort Study.
Introduction: Febrile illness are the most common reason for seeking healthcare in India and is associated with substantial morbidity and mortality.In view of the rising threat of dengue in the country, the incidence needs to be estimated using cohort study design. Various initiatives have been taken up -both by private and public entities for developing novel vaccines for tackling dengue fever for which sero-surveillance is necessary and will be undertaken. Thus this study will support these initiatives to understand the burden of the disease in the county and render the feasibility of the evaluation of safety and effectiveness of a reliable vaccine in the shortest possible timeframe We are proposing this community based prospective multi centric cohort study in the all the ten clinical trial network (CTN) field sites supported under DBT’s Resource of Indian Vaccine Epidemiology Network (DRIVEN) funded under National Biopharma Mission, Biotechnology Industry Research Assistance Council (BIRAC), Department of Biotechnology India. These sites cover the major endemic areas depicting geographical distribution of the disease across the country. The proposed study aims to assess the incidence of dengue fever across the CTN geographical coverage over a period of 1 year. Although the sample size is not powered for other disease indications (Chikungunya, Malaria, Typhoid, Leptospirosis, Scrub typhus), the study will also estimate the incidence of Chikungunya, Malaria, Typhoid, Leptospirosis, Scrub typhus and proportion of asymptomatic infections, secondary infections as well as describe the circulating dengue and chikungunya serotypes in the study area by lab confirmation of fever cases during the study period. The epidemiological data generated in the study will be useful in designing future vaccine trials, conducting the trials and impact assessment, which is in line with the mandate of DRIVEN’s Clinical Trial Network Objectives. Objectives Primary objective In the study area: 1. Estimate Prospectively a. Incidence rate of acute febrile illness episode during 12 months of follow up b. Incidence rate of symptomatic laboratory confirmed Dengue infection episodes during 12 months of follow up c. Incidence of Sero positivity based on IgG, IgM and neutralizing antibodies at 12 months (Sero Negative for IgG, IgM or Neutralizing antibodies at baseline at enrolment). Secondary objective 1. Incidence rate of symptomatic laboratory confirmed Chikungunya infection episodes during 12 months of follow up 2. Determine the etiology of AFI due to other common causes of AFI (based on rapid diagnostic or ELISA based laboratory diagnosis) a. Malaria b. Scrub typhus c. Leptospirosis d. Typhoid 3. Describe the proportion of symptomatic versus asymptomatic or sub clinical infections of dengue and Chikungunya based on data obtained from primary objectives. 4. Identify and describe the circulating serotypes of dengue and chikungunya in the general population over a period of one year. 5. To assess spatiotemporal trend of Dengue and Chikungunya infection over a period of 12 months. 6. Determine the durability of IgG, IgM and Neutralizing antibodies in symptomatic individuals tested n Positive for Dengue and Chikungunya infection. 7. Estimate the economic burden of dengue and chikungunya fevers based on information about: a. Patients with severe illness requiring hospitalization and / or ICU care b. Patients managed on out-patient basis.
Methodology Study design The proposed study envisages to establish population-based cohort and prospectively follow individuals within selected ten sites of India. The activities entailed would be: 1. Dengue and Chikungunya Sero surveys at 12-month interval 0 (baseline) and 12th (end-line) month. 2. Establish acute febrile illness surveillance through weekly follow up (self- reported; telephonic calls; and home visits) 3. All febrile episodes are investigated with Rapid and Laboratory diagnostic tests and sero surveys. Study Sites The prosed study is planned to be carried at 10 surveillance sites supported by the Department of Biotechnology - National Bio Pharma Mission (DRIVEN Network). Study Duration The study is planned for a period of 16 Months. It includes preparatory phase of 2 Month, 13 Months of data collection where a cohort will be established and 2 rounds of Sero survey (at baseline – Month 0 and end-line – Month 12) will be carried. Every individual will be followed for a period of one year. Inclusion and Exclusion Criteria Inclusion Criteria  Study will be carried out in individuals above 2 Years of age.  Individuals currently residing and likely to stay till the end of one year in the study area.  Consented to participate in both sections of the study (Sero Prevalence and AFI Surveillance) and follow all procedures. Exclusion criteria  Ongoing fever episodes or history of AFI on or within 3 calendar days before enrolment for the cohort Criteria for discontinuation of participant/ Loss to follow up  Out migration (permanent) of the participant from the study area or unavailability of the participant for more than six months. Sample Size Sample Size for Dengue Incidence and Sero Prevalence The sample size for the proposed study is calculated based on an assumed incidence rate of 5.0 dengue symptomatic cases per 100 person year of follow up, with a margin of error of 15 % (Relative precision), yielding a sample size of 3415. To account for up-to 10 % loss to follow up and Design effect of 2, the target number of individuals to be followed for a year is estimated as 752/site. Sample Size for Sero Prevalence of Neutralizing Antibodies The sample size for sero prevalence for estimation of Neutralizing antibodies is calculated, based on the prevalence of neutralizing antibodies as 47%23, absolute precision as 5%, 95 % Confidence Interval and 2.0 as design effect. A minimum sample of 100/site. Sampling Method: We will follow age Proportionate sampling technique where the individual enrolment will be based on the age proportionate bands and the age group proportion from the five selected clusters in the community. Study Procedure: Baseline Sero Survey: Day 0: A baseline round of sero-survey will be conducted in 752 apparently healthy and age stratified participants (afebrile cases with no established diagnosis of disease under surveillance) Serum samples collected from sero-surveys will be tested for IgG antibodies against Dengue and Chikungunya infection using laboratory based ELISA tests.All 752 participants will be followed up in a weekly basis by the study team for 12 months for acute febrile illness surveillance. If the participant develops fever then they will be included for AFI survey and evaluated for probable causes of AFI. End Line Sero Survey: Day 365 ± 30 days: After completing the baseline sero-survey, enrolled members of the cohort will be followed up for 12 months and then will undergo another round of sero-surveys at the end of one year to estimate the rate of sero conversion (365 ± 30 days since first sample withdrawal) after the first round
AFI SURVEY: Once a participant declares himself febrile (either by active surveillance or by passive surveillance), an alert will be popped up by the contacting team to the diagnostic team (if they are different). The diagnostic team will make visit to the participant (who can be at home or at hospital) and shall make attempt to establish diagnosis of acute febrile illness. Key steps to be followed: a. Confirmation of the diagnosis: The diagnostic team shall visit the participant and confirm the diagnosis of acute febrile illness (as per the definition under section 3.9). The details of symptoms including the date of onset and recovery and treatment sought will be recorded using standard case reporting forms. b. Acute Phase: (Day 3 – 7 of onset of fever) - If the visit has been made within 3 – 7 days of onset of fever, the participant is available for acute phase workup. Under this workup, in order to establish diagnosis of acute febrile illness the participant will be tested for Dengue (Using NS1, IgG and IgM ELISA Tests), Chikungunya (using IgM tests – only for seronegative individuals) and Malaria (using RDK) as the common causes of acute febrile illnesses. The participant will be facilitated to the nearest health care facility for further management. c. Follow up: (Day 10 ± 2 of onset of fever) – if the participant still complains of fever and diagnosis is not established till day 10 since onset, then a follow up visit will be carried. In this visit the participant will be tested for Typhoid using Widal test, Leptospirosis and Scrub Typhus using ELISA technique. d. Convalescent Phase: (Day 21±2 of onset of fever) – Irrespective of fever status, all participants who had AFI will be tested for dengue and chikungunya convalescent serology’ if or to understand the co – infection of dengue and chikungunya the convalescent visit will be made. In this visit paired testing of samples for Sero-conversion and four-fold rise in titers shall be evaluated. e. Unscheduled Visit: (Any Day): The study team or the participant can make any unscheduled visit to monitor the progress of febrile illness.
Data Management Data Collection Data collection will be done using a paperless data management platform (SOMAARTH-3). The software (developed with android module) will have inbuilt system for step by step data collection and checking process. This process shall reduce the time lag between data capturing and transmission and also allow rapid data review and rectification. The software would be piloted to ensure the logical flow and logic checks. The Data Management team of the INCLEN shall provide training and support on the use of these devices for data collection along with a detailed manual of operations and other research tools. Data will be synchronized into INCLEN server by data manager after preliminary cleaning preferably within 48 hours of collection of subject information. On regular basis the data received in INCLEN server shall be checked and verified by the data management team. The database shall have restricted access to authorized personnel at each site with strict security system. Log for access and modifications in data shall be monitored through the data management protocol. Data Analysis a. The incidence of Dengue, chikungunya and other vector borne disease infection will be estimated from the acute fever surveillance carried for a period of one year. The number of fever episodes, mean duration of fever and participants with rapid diagnostic and laboratory confirmed cases will be calculated using statistical tests of chi square and t test. [Primary & Secondary Objective 1 - 2 ] b. The Sero-prevalence of IgG antibodies and Neutralizing Antibodies will be calculated from baseline assessment of the Sero samples. [Primary Objective 2] c. The circulating serotypes will be calculated during the baseline and end line serosurvey and the samples obtained during the acute fever surveillance [Primary Objective 3]. d. The serial Sero survey at baseline and end line will be used to identify the incidence of asymptomatic cases of dengue and chikungunya [Secondary objective 2] e. Sequential neutralization antibody titers among those detected as Dengue / Chikungunya antibody positives will help to analyze the duration of persistence of antibodies. [Secondary Objective 4] .f. Economic burden estimation [Secondary objective 5]: A full economic analysis from a societal perspective will be conducted by combining the three major cost categories: direct medical, direct non-medical and indirect costs. Data analysis will be done using STATA. Descriptive analysis will be done to study population characteristics described as proportions (%) and mean (SD). Confidence intervals will be calculated. Association of demographic characteristics and sero prevalence will be calculated by univariate analysis using Chi-square test. Person Years (PY) of follow-up will be calculated as the amount of time contributed by the participant between enrolment and the end of the reported study period or withdrawal from the study. For participants who are lost to follow-up, PY will be calculated as the time between enrolment and the last contact with study team and one-half the time between the last contact and the date recorded as lost to follow-up. Overall incidence of dengue infection both clinical and asymptomatic per 100 PY will be analysed. The age specific incidence rate will be calculated as the number of new cases in the specific age interval divided by total number of person years of follow-up contributed by all the participants at risk in this interval using the Incidence Rate Ratio (IRR) calculator available in STATA.
Outcomes The proposed study is expected to determine the burden of diseases causing acute febrile illness with focus on Dengue and Chikungunya at community level and monitor to estimate the seasonal variations and rate of transmission in the incidence of disease, Risk factors for infection can be identified which might inform future control strategies. The serial surveys in the same set of individuals will help in measuring the antibody levels over a period of time and understand the proportion of individuals who are able to mount a neutralization response and the duration for which immunity lasts after infection. |