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Role of timing of vaccination in measles outbreak in Tathleeth region, Saudi Arabia, 2007, 1428H


Measles outbreak occurred in Assir region in 2007G (1428H). The highest number of cases was reported from Tathleeth sector (132 cases). This outbreak was being investigated to test the hypothesis of the role of delay in routine vaccination in the incidence of measles in the community. There are 5447 children registered in four PHCCs for EPI vaccination during period 2000-2005.There are 4154 children from Tathleeth PHCC, 1084 from Amwah PHCC, 622 from Jash PHCC & 587 from Subaikhah. These four PHCCs represent the bulk of health institutions in Tathleeth sector.


A retrospective cohort study for children registered in PHCCs for EPI vaccination during period 2000-2005 besides a descriptive cross-sectional study for current measles outbreak were conducted. The data was collected about current measles outbreak from all areas following Tathleeth sector and archived in Tathleeth general hospital. The formats were filled completely. The investigator collected data from the main four PHCCs (Tathleeth, Amwah, Subaikhah and Jash) for children registered in these PHCCs for EPI vaccination during period 2000-2005.


Regarding the descriptive cross-sectional study for current measles outbreak 132 cases were registered in Tathleeth sector. The peak of the cases was during April 2007 (51.5%) and the most cases(44.0%) besides the first case were registered in Tathleeth PHCC. 50.8% were females and 49.2 % were males. All were Saudis except one. 15.0 % cases residing inside Tathleeth city and 85.0 % cases were residing outside although 44.0% of cases were treated in Tathleeth PHCC. All cases experienced fever and skin rash. Among the whole cases 57.6% did not receive any vaccine. 13.6 % received partial vaccination. 28.8% were completely vaccinated. 97 cases were anti-measles IgM positive. In respect of the retrospective cohort study, during the study period from year 2000 to 2005 G (6 years), by the time of data collection (July 2007) among the studied children, 87.2 % had received at least one dose of measles vaccination and 12.8% of them were not vaccinated at all. Overall 33.1 % were completely vaccinated and 54.1 % were partially vaccinated. Almost perfect MMR1 vaccination pattern was observed in Subaikhah PHHC throughout the study period, while in other PHCCs vaccination was not so high. Jash showed consistent over 90.0% MMR1 vaccination with minor fluctuation, while Amwah showed a very high peak of 98.6% in year 2000 which dipped to only 21.0% in 2001 and since then had widely fluctuating vaccination percentages. Tathleeth showed a gradual uneven decline from 97.7% in 2000G to 75.4% in 2005G. Regarding the 2nd dose of MMR vaccine only 6.0% children received it. Despite overall low MMR2 vaccination rates, Subaikhah and Jash performed better than other PHCCs. 29.9% children received Measles vaccine as part of EPI vaccination program. As a result 95.1% of the children registered in 2000 and 78.7% of those registered in 2001 were vaccinated with Measles vaccine. And for these two years all the PHCCS performed well, Amwah performance was poorer than others and especially for the year 2000. When the vaccination status was stratified for the current age of the children, it was observed that 80.4% of the children 19-30 months and 84.4% of the children 31-42 months received MMR1 dose alone. Among the children 3.6yrs-4.5yrs 73.6% received MMR1 alone and 11.0% received MMR2, while among children 4.6yrs-5.5yrs 60.7% received MMR1alone and 21.9% received MMR2. However disappointingly, 77.4% of children 5.6yrs-6.5yrs old received MMR1 alone and 1.5% received MMR2, while 97.9% of the children 6.6yrs and above had received only MMR1 and only 0.2% children received MMR2 vaccine. Delay in MMR1 vaccination was defined as any child who did not receive his/her MMR1 or received MMR1 at or after 13th month of his birth. 50.7 % had delayed MMR1 vaccination. A proportion of those who had delayed vaccination did not show any specific trend and this has been fluctuating over the years between 41.9% and 60.0%. Within the PHCCs, Subaikhah performed better than others with 28.5% delayed vaccination and poorest in Amwah with 67.0% delayed vaccination. the best year for any PHCC was 2001 for Subaikhah with only 8.5% delayed vaccination and the worst was also 2001 for Amwah with 83.5% delayed vaccination. When delay in vaccination was assessed, keeping in view the current age of the children, it was observed that among the children 19-42 months of age 82.5% had received MMR1 before 13 months of age indicating that they were on schedule for the EPI recommendation for MMR1. Among the children 67-92 months of age only 9.1% received MMR2 and thus were on schedule, while 90.9% children did not receive MMR2 and thus were not on schedule according to EPI recommendation for MMR at this age. Although 16.3% of the children aged 3.6yrs-5.5yrs received MMR2 vaccine, but keeping in view the recommended age of vaccination i.e. 4-6 years, it is not possible to comment about the proportion not on schedule at this stage of observation, as some of them they may still get the vaccination in time.


The current measles outbreak in Tathleeth region is considered the first measles outbreak in this region and the most probable factors which led to its development are reduced herd immunity, low vaccine coverage and administration, increased number of susceptible, nature of vaccine against measles and regulation of measles outbreak. The revaccination of susceptible individuals and congested populations should be considered as well as an accurate vaccination schedule.