We identified a total of 1267 articles through our search strategy. Of these 239 mentioned a measles epidemic occurring between 1998 and 2009. We were able to obtain all of these papers. However, of these 239 papers, only 39 (14%) actually reported on outbreaks occurring in crises in countries where CAP/Flash appeals occurred. The 39 papers identified described a total of 37 outbreaks, in 29 (78%) of which a measles mass vaccination intervention was mentioned as having been used. Upon further review, only 25 papers were retained. Those 14 papers discarded reported either on mathematical models of potential interventions or reported on epidemics occurring outside of the time frame but with delayed publication or in one case on an epidemic in a hospital.
For each of these reports, some covering an outbreak in the same country, we attempted to determine objectively the impact of the measles vaccination intervention as it pertains to age range based on the data provided. Table describes the epidemiologic characteristics of the reviewed reports classified by region to provide context on measles control. Table includes details on the mass vaccination intervention noting in particular the time to the response (where reported) and if there was evidence of an impact.
Epidemiological Characteristics of Reviewed Outbreaks
Mass vaccination response details *
In the Americas [9
], there were no reports of preventive mass vaccination campaigns during the acute phase of a humanitarian emergency, but several reports of outbreak response immunization (ORI). An outbreak in Bolivia beginning in 1998 affected the country nationwide. A nationwide non-selective vaccination campaign, where children irrespective of their vaccination status are eligible for vaccination, was implemented four months after the first case was reported targeting children 6 m to 5 years with reported 85% coverage obtained in this age group. The following year house-to-house campaigns were performed in two departments of the country and in high-risk municipalities. In 2002, a house-to-house campaign was performed nationwide targeting children 6 m to 4 years with a reported 95% coverage and halt in transmission [9
Similarly, in Haiti, cases were reported in Gonaives beginning on March 8, 2000. A non-selective mass vaccination campaign (single visit, house-to house) targeting children 6 m to 14 years was implemented at the end of April, 2000 with reported 95% coverage. The last case in Gonaives was reported on May 3, 2000. Subsequent campaigns were repeated in Artibonite, Port-au-Prince and Delmas after cases were reported there [10
]. In Colombia, an epidemic in 2002 affected approximately one third of the country and a vaccination response was implemented door-to-door targeting children 6 months to 5 years in high risk areas. The authors posit that the prompt, although specific details of the delay are not given, door to door vaccination and surveillance may have prevented an even larger outbreak in a Colombia where routine services were limited by long-term conflict [11
Reports from Asia include two non-selective mass vaccination interventions in response to natural disasters in India [13
]. One response entailed the preventive vaccination of children in flooded areas of Bihar, where high population density and subsequent poor access to care placed the population at high risk. Non-selective vaccination of children 6 months to 14 years achieved an estimated 75% coverage. A total of 1811 measles cases were reported but there is insufficient data presented to determine the potential impact of this intervention, although the authors' qualitative analysis suggest that the campaign prevented a larger scale outbreak [13
The second report from India describes the emergency response to the Indian Ocean earthquake and tsunami of 2004. Non-selective preventive mass vaccination for children 6 to 60 months was conducted in 58 villages of Tamil Nadu province, where one-dose measles coverage was reported to exceed 95%, beginning December 29, 2004, four days after the tsunami. A cluster of measles cases was subsequently reported in a tsunami affected area on December 30 with cases reported in non-tsunami affected areas of the province soon after. Although the overall scale of the outbreak was small (n = 101), the authors conclude that the target age range of the preventive vaccination was too restrictive as more than half of measles occurred in children between 5 and 15 years cases in both tsunami-affected villages (56.3%) and non-tsunami affected villages (60%) [14
Two additional reports describe interventions in refugee populations [15
]. In Afghanistan, following the fall of the Taliban, an influx of approximately 2 million refugees returning from Pakistan and other neighboring countries was anticipated in early 2002. In response, non-selective vaccination of children 6 months to 12 years was conducted throughout 2002 reaching 82%-96% of the target population by the end of 2002 [18
]. The campaign initially targeted high-risk districts and cities with the largest number of susceptible children, and subsequently the most remote and inaccessible villages. A follow-up campaign was conducted in 2003, targeting children aged between 9 and 59 months. It is important to note that this campaign was prompted by the fact that an epidemic had occurred in 2001 affecting at least 7 of the 30 provinces in Afghanistan. Difficult access due to snow and mined roads and insecurity left many districts without heath services. The actual scale and scope of the 2001 epidemic is difficult to estimate, but a total of 8,762 cases were reported through the nationwide surveillance system, of which 33% of cases (n = 8762) occurred in children 5 to 12 years.
In Sri Lanka, a measles epidemic with a suspected 15,250 cases between October 1999 and June 2000 was reported [19
]. The outbreak began in Colombo and progressed to becoming countrywide. Response included actively searching for and vaccinating children under the age of 10 years at the local level who did not report previous vaccination. Non-selective vaccination in "welfare centers, refugee camps, preschools, and urban slums" was also conducted without specifying the age range or whether all locations were included. The authors report that they "specifically chose not to implement outbreak response immunization as the WHO recommends such activity only under specific conditions such as refugee camps, military barracks or closed communities." The authors provide insufficient information with which to assess the potential impact of the intervention, but it is important to note that of the 3728 measles cases with sufficient detail, 40% reported having been vaccinated previously and 69.4% occurred in children over 10 years.
In the African region [21
], two reports describe vaccination interventions in response to the nationwide epidemic in Niger in 2003-2004, where 50,138 cases were reported. A reactive campaign in the capital Niamey (n = 10,080 cases), targeted children 6 months to 5 years, 5 months after cases were reported [21
]. In Mirrah District, Niger, outbreak response vaccination was restricted to outreach vaccination services in some health centers, although the extent of these efforts was not well documented [22
]. The results of a retrospective household survey found two-thirds of case patients were under age 5 and 90% under the age of 10. The author's remark on the need to include children older than 5 years in vaccination activities as this may prevent deaths in infants who acquired measles from older children and also prevent deaths in older age groups, the rationale for the SPHERE recommendations. Mortality was inversely associated with the age of case patients, with the highest CFR in children under 12 months (15.7%; n = 13/83); followed by children 12-59 months (11.5%, n = 64/558); then children aged 5-14 years (5.4% (n = 14/259). In the same region, epidemics in Nigeria and Chad also occurred [23
]. There was no vaccination response to the epidemic in Nigeria. A non-selective campaign targeting children 6 months to 5 years, four months after cases were reported, was implemented in N'djamena, Chad in 2005. Although subsequent SIAs in Niger, Nigeria and Chad reported obtaining high coverage among the target population, outbreaks continue to be reported in this region.
In Tanzania, a report on an outbreak among Burundian refugees in four camps noted 31% of cases were between 6 and 15 years [24
]. A non-selective response targeting children 6 months to 5 years, initiated between one and five months after cases were first reported in each of the four camps reduced cases and deaths, however, the authors conclude that it would have been more effective to target a wider age range to halt transmission. A report on a measles epidemic in Gode, Ethiopia came to similar conclusion recommending that a wider age range than the 9 months to 5 years targeted in the response, which although prompt, could have contained the outbreak [25
]. The authors further note the poor coverage achieved by the intervention and potentially poor vaccine efficacy due to presumed problems in the cold chain.
In Darfur, Sudan, although cases were reported throughout the Darfur region, non-selective vaccination targeting children 9 months to 15 years was conducted only in North Darfur, reaching a reported 93% of the accessible population, but an estimated 77% of the total target population [26
]. Measles cases continued to occur after the intervention. The authors report difficulties accessing a population that was continually moving to avoid violence with the repercussion that new returnees to the camps were not vaccinated.
One report from Europe describes vaccination interventions in refugee populations [32
]. In Albania, an epidemic response was initiated only two weeks after a measles outbreak began among Kosovar refugees in 1999. The surveillance system allowed for early detection of the outbreak and a non-selective campaign for children 6 months to 5 years was implemented. An estimated 43% of the 80 cases were in persons older than 15 years.