To herald in our second (maybe third?) article of our series on vaccine-preventable diseases, China has recently started their massive measles vaccination program. They’re looking to vaccinate 100 million children who may have missed their last shot. You may have had measles as a kid and now wonder why the Chinese are spending $23 million USD to flush out this disease.
To start with, measles is one of the most contagious diseases we know of… To compare contagiousness, we use reproduction numbers (R0). R0 is the average number people infected by a single infected case. If R0 is less than 1, a disease cannot support itself and will eventually die out. An R0 greater than 1 means that an epidemic could potentially occur. Measles has an R0 of 10-15, which means each measles-infected person infects 10-15 people on average. In comparison, the 1918 Spanish flu had an R0 of 2-3. To put this in perspective, it would take 80 000 virus generations for Spanish flu to infect all of the 6.7 billion people of the world, but only 10 virus generations for measles.
The R0 is specific for a particular infectious agent in a particular population and many things can alter it. Some aspects are specific to the virus: for example, how much virus is made and spread by each infected patient, how much virus it takes to cause an infection, how long the virus remains infectious. Others are host-specific: such as, how strong the patients’ immune systems are, how many contacts each infected patient makes every day, what their habits are (high-risk behaviours like tattooing and needle-sharing can increase the R0). Disease control interventions are used to knock R0 down to below 1. This includes: encouraging wearing of face-masks to limit the amount of virus spread from an infected person’s cough; quarantine to decrease the number of contacts an infected patient makes; and of course, vaccination.
But if you’ve got it, so what? It’s just a rash; it’ll go away. This sort of thinking has led to “measles parties”, where parents intentionally expose their kids to measles. While not as horrible as chlamydia parties, this is still quite a dangerous practice. After an incubation period of 10-12 days, the majority of children will just get flu-like symptoms and a characteristic red rash. But, especially in children under 5 and those who do not have adequate nutritional intake, complications can develop.
If we take 1000 infected children: 1-10 of them will die (50-150 in developing countries) from complications; 80 will get diarrhea and resultant dehydration; 70 will get ear inflammation; 60 will get bacterial pneumonia; 10 will get infected sores on their eyes and become blind; and 1 will get potentially fatal brain-swelling. Measles currently causes 450 deaths per day in children worldwide. This is why we vaccinate against measles. There is no cure for measles. Vitamin A supplements and better nutrition may help to limit complications, but we’re wholly dependent on the vaccine to protect people from measles infection.
Yes, the vaccine itself is not perfect, but the benefits hugely outweigh the costs. For a thorough review of the side-effects of the measles vaccine, read the one in the references by Duclos and Ward. In summary, the vaccine very occasionally causes a depletion of blood platelets, severe allergic reaction, or inflammation of the brain (1 reaction per 30000, 100000 and 1000000 doses, respectively). But the children are alive in the end. They, and the people they interact with, are not exposed to the aforementioned complications of measles infection.
As an aside, the mealses vaccine was reported to have links with autism and Crohn’s disease. Large studies of up to millions of children have debunked these links. The measles vaccine is not associated with autism or Crohn’s disease.
Indeed, all vaccines (as with everything in this world) have risks. With perfect information, we could probably predict who would have a reaction to the vaccine and excuse them from vaccination. Alas, we do not have access to such information. It may seem like we are using exposing these children to risks as a matter of trial and error. It may very “two steps forward, one step back, then walk around in a circle for a bit”. Indeed the scientific process is the worst way to progress, except for all the other ways.
Vaccination is currently the safest, most effective way to prevent measles. This is what China is investing in: prevention of a highly contagious, potentially fatal disease for not only the current generation, but also those hereafter. With more programs like these, we may eventually see the end of measles and relegate it as a vestige of the past.
Duclos P, & Ward BJ (1998). Measles vaccines: a review of adverse events. Drug safety : an international journal of medical toxicology and drug experience, 19 (6), 435-54 PMID: 9880088
Amanna, I., & Slifka, M. (2005). Public Fear of Vaccination: Separating Fact From Fiction Viral Immunology, 18 (2), 307-315 DOI: 10.1089/vim.2005.18.307