Measles Epidemiology and Elimination Status in Oman
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Volume 1, Issue 3 Sultanate of Oman Ministry of Health Jul-Sep 2017 Inside this issue: Measles epidemiol- 1 ogy and elimina- tion status in Oman Public Health Sur- 7 veillance Round The success story 9 of North Sharqiyah campaign Measles epidemiology and elimination status in Oman National ARI Sur- 11 Global situation veillance Q2 data he global eradication of smallpox that vened by WHO in 2010, it was stated that T was certified by WHA in 1980, the scien- global measles eradication is biologically, technically and operationally feasible. Q2 (Apr-Jun 2017) 12 – tific community was looking for another can- Communicable 15 didate vaccine preventable disease for the In the meantime several countries have Disease Surveil- feasibility of eradication. Poliomyelitis and adopted measles elimination (cessation of lance data measles looked promising then, but both endemic transmission) as their national goal have proved elusive so far. The framework and many were able to achieve it in the past developed for smallpox eradication was sub- decade. In May 2012, the Global Vaccine Editorial Board sequently applied for polio and later for the Action Plan (GVAP) for 2012–2020 was en- measles, rubella and the Congenital Rubella dorsed by the 194 WHO Member States at Executive Editor: Syndrome (CRS) eradication program. the 65th World Health Assembly that called Dr Seif Al Abri The scientific world is currently debating on for the elimination of measles and rubella in Director General, DGDSC at least 5 of the 6 WHO Regions by 2020. On the choice of measles ‘eradication’ and the intermediate goals of ‘mortality reduction’ September 27, 2016, the Pan American Editor: and ‘elimination’ on the grounds that main- Health Organization (PAHO) verified that Dr Shyam Bawikar taining elimination is a costly affair. However the Americas had eliminated endemic mea- in the global technical consultation, con- sles transmission. Board of Directors (Departments) Fig.1: Indigenous* measles cases and vaccine coverage in Oman: 1975– 2017 (Jun) Surveillance Communicable Diseases Central Public Health Laboratory Infection Prevention and Control Environment and Occu- pational Health Contributors: Dr Shyam Bawikar Dr Padmamohan Kurup Dr Sultan Al Busaidi Dr Parag Shah Dr Prakash Patel *Indigenous measles case is a case resulting from endemic transmission of the virus (i.e. virus present in Note: For details of laboratory confirmed the territory for ≥12 months) as confirmed by laboratory testing or epidemiological linkage cases from 1995-2017 (Jun) refer to Fig.2 Public Health Bulleti n Page 2 Fig.2: Laboratory confirmed (IgM+) measles cases and rate per 100,000 population reported in Oman: 1995-2017 (Jun) “Measles elimination Measles elimination goal is defined as the Registry’ was established in 2001. The last case Measles elimination is defined as the ab- of CRS on record was born in the year 2006. absence of endemic sence of endemic measles transmission in measles a defined geographical area (e.g., region or The Ministry of Health introduced a number of measures as a step towards elimination of transmission in a country) for ≥12 months in the presence of a well-performing system. measles, rubella and the CRS. A mass catch-up defined campaign was conducted in March 1994 tar- It means that countries should be able to geographical area geting children aged 9 months to 18 years irre- demonstrate to the review and certification spective of their previous immunization status. (e.g., region or commission, the evidence of a robust immun- A combined vaccine containing Measles and country) for ≥12 ization program with 2 doses of measles- rubella (MR) antigens was used in the house-to months in the containing vaccine (MCV2), a functional -house and the school campaign. Ninety four strong surveillance system and the absence presence of a well- percent of target population was covered. In of measles case/s due to local endemic geno- the same year a second dose of measles performing type in the past 3 years. The laboratory ca- (MCV2) and a first dose of rubella as MR vac- surveillance system.” pacity will be examined in parallel and the cine was introduced at 15 months in the child- classification of measles cases will also be hood immunization program. From April 1996 thoroughly scrutinized. a case-based surveillance was announced for Elimination milestones in Oman measles and rubella i.e. all the clinical cases Sultanate of Oman introduced the measles were subjected to serological test (IgM) for vaccine (MCV1) in EPI at 9 months since early both viruses for confirmation in the Central eighties. From the year 1990 the vaccination Public Health Laboratory. With these actions coverage for all antigens in the schedule re- the Ministry of Health had taken its first tenta- mained high (>95%). tive step towards the goal of elimination of measles and rubella infection in Oman. The country faced its last major simultaneous outbreak of measles and rubella in 1992-93. Subsequently the national goal of elimination Over 3,000 clinical measles cases were regis- of measles, rubella and the CRS was officially tered nationwide. In the following years (1993 endorsed from the year 2001. The fever and -94) a surge (>60 cases) of congenital rubella rash (F&R) surveillance was launched with se- syndrome (CRS) was noted in newborns due rological confirmation and epidemiological to maternal rubella infection during the out- investigation. Under this strategy all fever and break. The measles incidence dropped signifi- rash cases were presumed to be measles or cantly with MCV1 coverage consistently rubella unless otherwise proved by serology. above 95 percent since 1995. From the year 2004, the F&R surveillance pro- gram was further strengthened by developing The rubella incidence also declined due to the algorithm and national guidelines and also use of a combined vaccine. A ‘National CRS conducting training workshops to sensitize the Volume 1, Issue 3 Page 3 clinicians. In the early years the target of 2 cas- reported. The median duration of clusters was es of F&R cases per 100,000 population was 9 weeks. The lowest incidence was observed maintained and from 2004 onwards far ex- with 1 laboratory confirmed case in 2003. ceeded. The CPHL was recognized as a WHO-EMRO, The schedule of MCV in EPI was changed to 12 Regional Reference Laboratory (RRL) for mea- and 18 months from October 2006. A limited sles in the year 2004. Measles PCR and virus SIA campaign was conducted in 2007 targeting isolation, genotying and sequencing was intro- non-national students aged 15-18 years from duced in 2007. the private schools of Muscat governorate with Measles serosurvey 2016 high coverage (99.6%). A sample of anonymous residual sera from Postpartum rubella vaccination (single dose) Omani population were tested by quantitative was introduced in 2001. The campaign contin- assay for measles antibody titre (IgG) ued for the following years. The HCWs as a Sample size was proportional to population high-risk group was also vaccinated with MMR. “Subsequently the and stratified for age and gender. The repre- Description of measles clusters during sentative sample was assigned to hospital la- national goal of the elimination phase in Oman boratories in the Governorates in Oman. Re- sidual serum samples from inpatients/ elimination of With the catch-up campaign in March 1994, outpatients available in hospital laboratories measles, rubella introduction of MCV2 in 1994 and the case- was collected and tested. Age was the only based surveillance from April 1996, the num- information collected. The cut-off point for and the CRS was bers of measles cases started declining. How- immunity was measles specific IgG >200 IU/ml. Total 1,990 samples were tested, officially adopted Table-1: Lab-confirmed measles in Oman: 2000-2015 of these 1,666 (84%) were sero- from the year Governorate positive. Six samples had no de- 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Total Muscat 1 1 2 1 1 6 1 2 5 1 6 3 5 35 tectable antibody level (0.3%). 2001.” Dhofar 1 6 2 6 1 1 16 4 3 2 2 3 47 N Batinah 1 1 1 7 1 7 4 2 9 1 1 35 Assuming high vaccination cover- S Batinah 1 14 2 1 1 1 3 11 34 age the Geometric Mean titres Dakhliyah 3 1 1 2 1 13 1 22 (GMT) were plotted against fol- N Sharqiyah 6 1 2 2 1 12 S Sharqiyah 4 3 1 3 11 lowing age groups according to Dahirah 12 2 1 1 1 2 19 measles vaccine doses received Buraimi 2 2 Musandam 1 1 2 1. Not due for MCV1: <12 months Al Wustah 1 1 2. MCV1 only: 12-18 months Total 9 15 4 1 17 33 13 8 9 20 6 7 10 22 24 22 220 3. MCV1+MCV2: 18m-22 yrs ever small clusters continued to occur. In these 4. MCV1+Catch-up: 23-40yrs measles infection was confirmed in adults and 5. No vaccine: above 40yrs unvaccinated or partially vaccinated children. Description of clusters of 2016/2017 In a cluster in Mudaibi (2000) 6 cases were re- Oman witnessed large clusters of measles last- ported after investigations the index cases ing for several weeks during 2016 until June could be identified (Indian child), similarly in 2017. The event set off worries whether the another cluster from Buraimi (Dhahira) in 2001, gains of the past in the elimination efforts will 13 cases were reported from a school (Index be compromised. case-Yemeni boy). Total 178 laboratory confirmed cases of mea- A total of 220 confirmed cases were reported sles were reported in 2016 and 2017 (June) in in Oman from 2000 until 2015 comprising of 12 nine clusters with following details: clusters and isolated cases with unknown 2016 source of infection from the regions of Dhofar, 114 cases of measles were laboratory con- North and South Batinah, Muscat, and Dakhli- firmed with 3 distinct clusters yah.