Why do measles outbreaks occur in middle and higher-income communities?
By: Robin Biellik, DrPH
Measles disease is easy to diagnose and measles vaccine is cheap and accessible. So why are we seeing continued and, in some cases, increasing measles incidence in middle- and higher-income communities around the world? In the past few years, despite a declining trend globally, reported measles incidence has increased in a number of middle- and higher-income countries in Western Europe, Southern Africa and, to a lesser extent, the Western Pacific[1].
In 2011, more measles cases were reported in the U.S. than in the previous 15 years. Most of these cases were related to exposure to measles imported from overseas.
Of particular concern is the growing number of major measles outbreaks in Europe, with the largest numbers of cases and deaths reported from Bulgaria, France, Germany, Romania, Spain and Switzerland[2],[3]. The causes of this phenomenon have been analyzed in depth and include, among others, lack of access due to social ostracism (Roma communities, immigrants), health system reforms that reduced resources for outreach services, vaccine refusal on the grounds of philosophical and religious beliefs, inadequate perceptions of the risks and benefit of vaccination among health care providers and the public, and anti-vaccine advocacy.
For some time, public health authorities have been aware of a growing trend among parents in middle- and higher-income communities of selectively or totally declining to vaccinate their infants against vaccine-preventable diseases. Many parents and their private physicians have not seen cases of vaccine-preventable disease for many years and believe they no longer pose any health threat. They are scared by reports of alleged vaccine-related adverse events they read in the media and on-line, and unaware that following scientific investigation most of these adverse events turn out to be unrelated to vaccine[4].
Anti-vaccine campaigners occasionally achieve national notoriety. Adverse publicity concerning DTP vaccine spread through high-income countries in the 1970s resulting subsequently in reduced vaccine uptake, a major pertussis outbreak, and many avoidable deaths[5]. This phenomenon occurred again in the past decade when falsified data linking measles vaccine and autism caused reduced vaccine uptake and a substantial accumulation of susceptible individuals, who now, as teenagers, have contracted measles during the recent outbreaks. Most recently, we witnessed how a US Congresswoman made unsubstantiated negative statements about HPV vaccine and declined to retract them.
The publication of anti-vaccine books, articles, websites, blogs and radio spots targeting well-educated parents has escalated enormously in recent years. In Western Europe and North America, anti-vaccine books on the shelves of bookstores’ health sections often outnumber evidence-based public health publications. Personally, I recall a poignant appeal by a WHO secretary during a meeting a couple of years ago who told us how, as a mother of young children living in France, she felt intimidated by the morning radio shows that relentlessly attack vaccination and brand parents who vaccinate their children as reckless and irresponsible.
But the public health community knows very little about the sources of these anti-vaccine books, articles, websites, blogs and radio spots, about who writes them, and who pays for them. Indeed, this blog article may attract more comments from anti-vaccine proponents than vaccine advocates.
Little systematic research has been conducted on the agenda of anti-vaccine activists, their methods and their funding. It will continue to be extremely difficult to counter this powerful lobby and its appeal to middle- and high-income parents until we learn a great deal more about where it comes from and how it operates.
Dr. Robin Biellik has 40 years experience in public health, primarily in vaccine-preventable disease control, elimination and eradication. He has worked for UNHCR, UNICEF and spent 17 years with WHO in the Americas, Southeast Asia and Africa. Now retired and consulting, Dr Biellik continues his work in immunization for organizations including WHO, the London School for Hygiene and Tropical Medicine and the Bill and Melinda Gates Foundation. He also serves on several expert committees on immunization and is an invited reviewer for several medical journals.[1] WHO Weekly Epidemiological Record, 87(5):45-52; 2012 – www.who.int/wer
[2] WHO Weekly Epidemiological Record, 86(18):173-174; 2011 – www.who.int/wer
[3] CDC Morbidity and Mortality Weekly Report, 60(47):1611-1614; 2011 — www.cdc.gov/mmwr/
[4] Mulholland et al. Confidence in vaccines in developing countries: social, cultural, economic and political influences. J. Epidemiol Community Health2010;64:563-564 doi:10.1136/jech.2008.085712
[5] College of Physicians of Philadelphia. History of anti-vaccination movements – on-line at http://www.historyofvaccines.org/content/articles/history-anti-vaccination-movements
Robin – nice post about a really important topic.
How far would you attribute measles outbreaks to problems with the vaccine? I know that some people have called for a review of the current strain used and possibly introduction of improved vaccines. For example, I know that following administration a few people will fail to mount an effective immune response.
Also – the same kind of outbreaks are happening in the same countries but with mumps. And in this instance it may have something to do with the vaccine as well.
I wrote about these topics on my blog a few months back:
Do we need a new measles vaccine? http://ruleof6ix.fieldofscience.com/2012/01/do-we-really-need-new-measles-vaccine.html
What’s causing the recent mumps outbreaks?
http://ruleof6ix.fieldofscience.com/2011/10/mumps-outbreaks-why-here-why-now-and.html
(Note the Measles Initiative is posting this on behalf of Dr. Robin Biellik)
Dear Connor:
We do not attribute the current measles outbreaks in middle- and high-income countries to problems with the vaccine. Measles vaccine has an efficacy of about 85% when given at 9 months of age (as is the case for the first dose in most developing countries), and over 95% when given at 12 months of age (as is the case for the first dose in most developed countries). We recommend a total of two doses, given by a variety of strategies including routine services and mass campaigns, which together provide lifetime immunity to measles to over 99% of individuals. Today, most measles vaccines are combined with rubella vaccine (MR) and mumps vaccine (MMR). The combination with rubella and mumps vaccine does not reduce the efficacy of the measles component.
In countries where vaccination coverage is sub-optimal, a group of susceptible individuals accumulates in the population until it is large enough to sustain an outbreak when the virus is introduced from outside the population. For example, with 80% coverage with MMR vaccine, a country will eventually experience a measles outbreak when measles virus is introduced, or may experience a mumps outbreak if mumps virus is introduced, or both if they are introduced simultaneously.
Therefore, in conclusion, there is no urgent need for the development of a new measles vaccine. The only justification would be to produce a liquid vaccine, rather than the current freeze-dried vaccine, which would be operationally more user-friendly for health workers. However, given the massive investment required for new vaccine development, that has not been identified as a public health priority.
Outbreaks are caused by failure to vaccinate, not vaccine failure, in the vast majority of cases.
Thank you, Robin.
You’re absolutely right to say too little research has been done on the phenomenon of anti-vaccine websites. It’s odd that scientists and doctors have been so slow to apply the scientific method to this aspect of public health.
There are plenty of ideas about why the movement exists and why it has been so successful (given it’s small size) but not enough research on the subject. Striving for ‘evidence-based communication’ efforts seems like a sensible approach.
Much more research is need to understand how social networks – online and offline – are influencing decision-making. But there is also much to be borrowed from the communication, social and behavioural sciences so perhaps it’s a matter of people from different corners of academia talking to one another to tackle this growing social issue.
The only snag is that embarking on new research projects can be a slow process and, with tens of thousands of new measles cases recorded in Europe in each of the last two years, there is little time to waste.
Pulling together existing knowledge and applying it might be more efficient. In the age of Twitter, arguments can be lost while we’re thinking of the perfect response. We’ve just got to get out there, take our message to where people are, listen, and engage.