There are a few species that we would gladly see extinct. Serious disease-causing pathogens are among the select few.
Ever since the end of the 18th century, when English physician Edward Jenner first noticed that humans vaccinated with fluid from cowpox lesions developed immunity against smallpox, people have searched for new vaccines that provide protection against deadly pathogens.
Vaccination against smallpox on a global scale was the first, and so far, the only, complete success in the effort to completely eradicate a disease, and has resulted in no new cases being reported for several decades. What was required for it to be successful? First, the vaccine had to be efficient, meaning that an immunized person should have a very low chance of getting the disease. Second, it had to be administered globally to achieve critical coverage.
Not all people can be vaccinated, as it can be dangerous for those with immunodeficiency and infants, nor is it necessary. What is needed is that in each community, there should be a high proportion of individuals who have received the vaccine.
If this proportion is above the critical coverage level, then the community has herd immunity. In such a community, even those few who cannot get individual immunity through vaccination are protected, because new cases will be isolated, and the disease does not spread. Herd immunity, with time, leads to fewer new cases and eventually to complete eradication.
Measles is a highly contagious preventable viral disease that can cause severe complications and even death, especially in very young children who are too young to be immunized, adults and in immunocompromised individuals. It was on the right track to eradication, and the number of new cases worldwide was steadily decreasing until 2016.
But since 2016, there have been successive yearly increases in cases, indicating a concerning and continuing upsurge in the overall measles burden worldwide. A recent report by the World Health Organization (WHO), ‘New measles surveillance data from WHO’ (https://www.who.int/immunization/newsroom/new-measles-data-august-2019/en/), reported: ‘In the first six months of 2019, reported measles cases are the highest they have been in any year since 2006, with outbreaks straining health care systems, and leading to serious illness, disability, and deaths in many parts of the world. There have been almost three times as many cases reported to date in 2019 as there were at this same time last year’.
The report went on to say: ‘The United States has reported its highest measles case count in 25 years. In the WHO European region, there were close to 90,000 cases reported for the first six months of this year: this exceeds those recorded for the whole of 2018 (84,462) – already the highest in this current decade’.
Deficit in global coverage
So why have we seen so many new measles outbreaks across the globe in 2019? The first requirement for eradication is fulfilled, as double MMR (measles, mumps, rubella) vaccination gives over 97% immunity to those who receive it.
However, worldwide coverage has been insufficient. Measles is one of the most contagious diseases, meaning that the required coverage for herd immunity is very high; for the first dose it is around 95%, which is difficult to achieve.
Global coverage with the first dose of measles vaccine reached around 85%, but did not increase in the past few years, and the coverage with the second dose is still only around 67%. An additional problem is that there are considerable regional and local differences in coverage. Gaps in vaccination coverage leave communities at a high risk for an outbreak, where the disease easily spreads from one unprotected individual to the next.
The reasons for the gaps differ according to region. In Africa, which has seen the largest increase (700%) in the first half of 2019 compared
to the previous year, the main reason is a lack of a strong primary healthcare system, leaving many small communities without access to vaccination. These pockets of low vaccination coverage are the hotbeds of measles outbreaks. In addition to gaps in healthcare provision, many countries have witnessed serious conflicts recently, leading to displacement of large populations. These populations do not have access to even the level of healthcare that was available in their home countries, exposing individuals to a high risk of infection.
In contrast, in European and most other developed countries, access to the measles vaccine is not the issue. In these countries, the reason for a lack of vaccination is two-fold. Firstly, the success of the measles elimination campaign meant that fewer and fewer people encountered the virus and people became complacent and started to believe that it does not pose such a high risk to their children, therefore they did not put enough emphasis on keeping up with the vaccination regimes present in these regions.
Secondly, since 1998 — when discredited British physician Andrew Wakefield’s fraudulent paper that linked the MMR vaccine to autism was published in The Lancet — anti-vaccination movements mushroomed. They spread misinformation across all media, planting doubt in parents’ minds about whether it is best for their children to be vaccinated.
Even though this paper was retracted in 2010, and several, large, well-designed and well-executed studies have shown that the MMR vaccine does not cause autism, it has proven to be very difficult to counter the damage that has been done.
In order to fight off measles and get it back on track for elimination, several adjustments have to be made. It is essential that primary healthcare systems are improved in poor countries and vaccination campaigns are instituted to access people in remote locations via efforts supported by international organizations.
But it is equally important to introduce legislation making the measles vaccination compulsory for children attending school. This will help to achieve higher vaccination coverage in developed countries. Finally, the perception of measles and vaccines needs to be corrected by giving clear and accessible information to people on the risks associated with refusing the MMR vaccine.
The author is an assistant professor at Hamad Bin Khalifa University’s College of Health and Life Sciences in Qatar.