Measles is an extremely contagious disease that gains ground as soon as immunization coverage drops. The vaccine is effective for about 85% of children immunized: out of 100 immunized children, 15 will be non-responders and as such unprotected. A second dose is therefore needed.
If the unvaccinated children are combined with these non-responders, a larger and larger group is formed over the years and becomes large enough for an outbreak to occur. Coverage should be very high and should be maintained at this level to limit the number of cases and deaths and prevent the onset of epidemics. On average, an immunization coverage of 80% will translate into occasional cases and deaths and a risk of outbreaks at intervals of five years or more.
At 60% coverage, there are more cases and deaths; outbreaks occur frequently – about every three years.
Measles epidemics are turning up just about everywhere. Can the current situation be described as exceptional?
“A situation like this has been unusual for several decades. It has been about twenty years since I have seen measles epidemics in this many countries and with this many cases. Over the past two years, we have seen some truly region-wide outbreaks, primarily in southern African, but also in the west and the center.
“There have been over 64,000 cases and 1,188 deaths in about 30 African countries between the end of 2009 and the first months of 2010, according to incomplete data from the WHO (World Health Organization). We have also seen the return of major epidemics, such as the outbreak that occurred in Burkina Faso last year and resulted in over 53,000 cases and approximately 340 deaths, mostly in children under five years of age.
“This year alone, there have been more than 8,000 cases in N’Djamena, the capital of Chad; the measles epidemic in Malawi has brought with it over 9,000 recorded cases since January.
“These epidemics strike countries one after another despite their routine and catch-up immunization activities. Today, a large number of countries have decreasing measles immunization coverage of children under one year of age. For other countries, there is the question of what is their real coverage, is it actually lower than what is advertised?
“This is a very rude awakening, which comes despite some very real success that has been recently achieved against this disease.”
Does this resurgence point to a failure in the prevention strategy used recently?
“The measles initiative includes two immunization strategies: routine immunization of children 9 to 11 months of age, and regular catch-up campaigns for children nine months to five years of age. That this strategy is well-suited for reducing the number of cases and mortality, there is no doubt. Nonetheless, it is essential to strengthen the fight against measles by vigorously addressing multiple problems: we need to go beyond slogans such as ‘Let’s eradicate measles’ to consider the limits of the current strategy’s implementation. It is no longer possible to be in awe of existing achievements and ignore what is not working.
“First, the outcomes of the prevention campaign for children under one year of age are not sufficient. The reasons for this are myriad. The EPI (Expanded Programme on Immunization) is effective but rigid: the period of time during which a child can be immunized is short – between nine months and one year of age.
“A common observation about our programmes is that many children over one year of age are not immunized and still cannot be given the vaccine, even though they are at high risk. They no longer fit in the framework of the EPI. Add to this multiple technical constraint, operational limitations, and limited access to care. More flexibility is critical to successfully adapting to certain environments and to increasing the immunization rate in those environments.
“Secondly, catch-up campaigns are critical to immunizing those children who were not immunized in their first year of life, as well as to limiting the number of non-respondents1 (15% of the immunized) by giving them a second dose of the vaccine. We have to notice that the implementation of these prevention campaigns is at present sub-optimal, primarily because of a lack of financial support.”
So has this been a false victory over measles?
“According to the World Health Organization(WHO), the deaths of 12.7 million people, mostly children, have been avoided between 2000 and 2008 thanks to prevention campaigns around the world. There is no dispute over this achievement.
“We are probably paying for this success now – since measles is no longer a massive cause of death, this disease is no longer a political priority: not in the Ministries of Health who have to make priorities, and not for the donors who are now reducing their contributions. There has also been a decrease in vigilance among health actors. More and more often practitioners who have never seen a case of measles! However, with this disease (as with others), a constant effort must be maintained – if not, all the gains made can quickly disappear.
“This success, real but fragile, might be strengthened and sustained, but only if adequate support and commitment are provided continuously at every level. In order to strengthen and maintain immunization coverage and improve case management and epidemic response, measles must be re-cast as a major health challenge at every level of the national health system and the competent institutions (WHO and UNICEF), as well as in the eyes of the donors.”
Does outbreak response also present a problem?
“Yes, the field teams are often faced with difficulties. The identification of epidemics depends on national surveillance systems that are more are less responsive. As soon as an epidemic is confirmed, support for patient care is generally organized without any problem. However, we often do lose extremely precious time in negotiations to define which immunization strategies to use to stop the propagation of the epidemic. For many years now, the epidemiological research center Epicentre has been documenting the response to measles epidemics.
“The efficacy of vaccination campaigns is rapid and proven: two weeks after immunization, the epidemiological curve drops steeply. Last year, new recommendations were finally issued by WHO in favor of responsive immunization campaigns under outbreak conditions, when the risk of propagation is high. Unfortunately, these recommendations were distributed confidentially.
“Because these recommendations were not integrated into national programs or by partners, technical discussions in the field about the outbreak response strategy, age distribution, and geographic area have all resulted in additional delays – sometimes significant ones – in initiating an immunization campaign. Likewise, no funding is available.
“We frequently encounter confusion between an outbreak response immunization strategy and a catch-up immunization campaign. Faced with these epidemics, there is the temptation – pressure even – to mobilize response resources toward catch-up campaigns and to widen the response to the entire country, with significant time commitments. At this point, the outbreak becomes an opportunity to conduct a catch-up campaign instead of to immunize to control its spread. However, to be effective, immunization during outbreaks should be rapid and targeted.”
Why are nations tempted to transform an emergency response into a prevention campaign?
“In the experience of MSF, emergency immunization during outbreaks costs about 1.5 per child vaccinated, whereas preventative immunization is estimated to cost less than $1 per child. But the donors are not the same. When responding to an outbreak, nations are able to find specific funds. However, the funds available to finance catch-up campaigns are now in decline. They are also sometimes delivered late – only a few months before a campaign – which limits the time available for organization and poses the risk of reducing the campaign’s quality and efficacy.
In this setting, the temptation is great to transform an outbreak response into a national campaign. As such, our teams face discussions which are as much political as they are technical.