CHALLENGES AND TARGETS FOR MEASLES ELIMINATION.

Monday, 20th of May 2013

[source]Lancet[|source]

As evidence mounts that the elimination of measles is faltering, Talha Burki looks at the scale of the problem worldwide, and what is being done to fight back against the disease. More details are available at: http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70133-6/fulltext

Earlier this year, WHO warned that worldwide measles control efforts have stagnated. More than half of the 20 million children who did not receive the first dose of the measles vaccine in 2011 (the most recent year for which statistics are available) are concentrated in five countries. Three of these—Democratic Republic of the Congo (DRC), Nigeria, and Pakistan—are currently in the midst of destructive epidemics. Meanwhile, Europe has seen a resurgence of measles over the past few years. Indeed, as The Lancet Infectious Diseases went to press, the number of cases in the measles epidemic that began in Wales last November has exceeded 1,200. Couple this with a sizeable funding shortfall, and it is hardly surprising that the drive towards the elimination of measles is faltering.

As things stand, only the western Pacific region seems likely to achieve elimination (defined as the interruption of all endemic transmission) in the foreseeable future. WHO reckons that endemic transmission has probably been restricted to four of the 37 territories within the region. From 2008—2012, the number of reported cases in the western Pacific fell by 93%. Much of this is down to China, where vast national immunisation campaigns prompted a 96% drop in cases. “The western Pacific is making excellent progress”, agrees Peter Strebel (WHO, Geneva, Switzerland). They have established a regional verification commission as well as national groups to review country-by-country progress and collate evidence.

If the western Pacific is declared measles-free, it would join the Americas in having eliminated the disease, which did so in 2002. Indeed, 2000—11 saw great advances in the fight against measles: deaths decreased by 71%, global coverage with the first dose of vaccine rose from 72% to 84%, and the number of countries providing the second dose through their routine immunisation services increased from 97 to 141. Those 11 years saw more than 1 billion children vaccinated. But another statistic throws light on the situation today. In 2007, funding for the Measles Initiative (relaunched last year as the Measles and Rubella Initiative) was US$160 million; in 2011, they received $80 million. The Initiative, a partnership between the American Red Cross, the US Centers for Disease Control and Prevention (CDC), UNICEF, WHO, and the UN Foundation, is currently facing a shortfall of $171 million for its activities over the next 3 years.

This is a major problem, explains UNICEFs Robert Kezaala. “Pakistan is cutting back programmes, and we have had to cut back finances for activities in Sudan and in Ethiopia”, he told TLID. “Unless funding goes back to its 2007 levels we will not be able to reach our targets.” Measles control efforts are based on a two-pronged strategy: strengthening of routine immunisation systems and roll-out of supplementary campaigns in those countries with weaker health-care systems. These usually take place every 3—4 years, targeting children less than 5 years old, and covering the entire birth cohort since the previous effort. Budget cuts mean that fewer vaccination teams are deployed, the targeted age range might be narrowed to children younger than 4 years old, and, on occasion, campaigns are delayed. “Delayed campaigns lead to outbreaks because you have a build-up of susceptible children—weve seen this happen in Africa”, points out James Goodson (CDC, Atlanta, Georgia, USA).

Africa has targeted 2020 for measles elimination. That this goal remains conceivable is in no small part down to GAVI. The organisation continues to fund introduction to the second dose of measles vaccine and, last year, it opened a new funding window to build on its initial investment of $247 million. More importantly, GAVI has offered a $550 million commitment stretching to 2018 for all 53 eligible countries (most of which are in Africa) to introduce the measles—rubella (MR) vaccine in joint campaigns targeting children younger than 15 years.

Still, on its own this investment is unlikely to push the continent over the finishing line. First, the epidemiology of measles in Africa is shifting. In many measles outbreaks, a third of cases are in adults. Goodson recalls how the Americas eliminated measles by targeting adults, as well as children, in the initial MR campaigns. “So when they introduced the rubella vaccine, they also covered the remaining susceptibility for measles, which was lingering among adults.” But for Africa, this is not feasible, given the funding shortfall and the security, infrastructure, and logistical problems that attend some of its endemic countries.

 

Full-size image (63K) C McNab/Measles & Rubella Initiative 

Catch-up vaccination campaigns in India have targeted 134 million children

DRC, Ethiopia, and Nigeria are highly susceptible to measles outbreaks. Between them, they reported in excess of 150 000 cases in 2011, almost half the reported total worldwide. “These countries have much weaker programmes, they really struggle to get first dose coverage above 70%, and for measles you really need 95%”, notes Strebel. Taking into account the vaccines efficacy, nearly half of all 1-year-olds are left susceptible to measles; this fuels regular large outbreaks. Supplementary campaigns have found it difficult to access all areas; in DRC and Nigeria, security is especially precarious. Ethiopia is in slightly better shape but all three countries face serious structural problems—the routine immunisation system in parts of northern Nigeria offers measles vaccine coverage of 30%. “They will have to do a lot of preparation, supervision, and monitoring to improve their campaign quality”, concluded Strebel.

Moreover, these countries all contain sustained reservoirs of circulating measles virus. “These are going to continue to cause a problem for the entire region”, said Goodson. That measles is a seasoned traveller is not under dispute: the 2009—10 resurgence that struck southern Africa has been attributed to a virus strain common to the west of the continent. But southern Africa is better equipped to combat measles. “They generally have more robust programmes”, notes Strebel. “Until the resurgence, they were doing very well, and even afterwards they mounted strong responses and incidence backed down.”

The exact decrease in incidence is unclear—Goodson reckons that Africas surveillance systems capture 10—30% of the total case load. Given measles role as an underlying cause of pneumonia and malnutrition, there is an enormous global mortality; WHO estimates 158 000 deaths for 2011. For India, WHO figures suggest 29 339 cases of measles in 2011. The real number is probably several times greater—this is a nation with a sizeable number of poorly nourished individuals, a highly mobile population, and crowded conurbations. Moreover, the country has traditionally disregarded measles; in 2008, 75% of worldwide deaths from the disease occurred in India. Before 2011, it relied on a single dose of vaccine and declined to do any supplementary campaigns. But, heartened by its success in eradicating polio, India is now turning its attention to measles.

Along with other countries in WHOs Southeast Asia region, India has put a lot of effort into strengthening its routine immunisation system. It is in the final stages of a vast catch-up campaign aimed at vaccinating some 134 million children in the 14 states with the weakest immunisation programmes. The remaining states have introduced the second dose of vaccine; the others will follow. “The districts which have implemented the supplementary campaigns have already seen a major reduction in measles incidence, and we expect to see both cases and deaths in India come down substantially—it will certainly no longer contribute such a hefty proportion of the global burden”, said Strebel. There are also moves to establish an elimination target for the region, probably 2020, which would serve as a de facto global eradication target.

For the European and eastern Mediterranean regions the target is 2015. WHOs eastern Mediterranean region encompasses countries such as Pakistan—which has yet to eliminate polio—and war-torn nations such as Somalia, Syria, and Yemen. The Measles Initiative built on the laboratory and surveillance infrastructure established for polio campaigns, which also offered precedents for operating in arenas of conflict, but 2015 still looks out of reach, particularly given the dearth of resources.

According to current trends, Europe too is likely to miss its target. Resistance to vaccination, particularly in Western Europe, has prevented vaccine coverage from reaching the 95% benchmark. Predictably, measles returned. In 2009, Europe saw 7,499 cases; 2 years later, the caseload exceeded 30 000—France alone saw 14 449 cases in 2011. There are all kinds of reasons behind this resurgence: measles has been dormant for so long that Europeans have forgotten how vicious the disease can be; there is growing, unwarranted mistrust of vaccination; and people are becoming over-reliant on herd immunity. The fact that nearly half the recent cases on the continent have occurred among adolescents and young adults testifies to historic gaps in immunisation programmes; perhaps attributable to delays in introducing the second vaccine, or parental reluctance to accept the MMR vaccine. Furthermore, convinced that arguments in favour of vaccination have already won the day, politicians and health-care professionals have been slow to react to antivaccination campaigns and public misunderstandings.

“It comes down to communicating the benefits of vaccination and I dont think weve adequately got our message across”, said Strebel. Resolving this should be straightforward. After all, there was a time within living memory when measles killed more than 2 million people every year, and blinded several thousand. Communicating the benefits of its elimination should not be a hurdle that campaigners fail to clear.