The video below discusses how to solve the question using a stepwise approach. The solution is included in a handbook with other examples, available on Kindle and the Apple iBooks store.
This discussion is based on Question 1 of the Sample Calculation Paper, December 2018, from the GPhC
The past few months have seen a rising crescendo of news articles highlighting a growing global measles epidemic and crisis. The following list is drawn from just the BBC alone.
- 20 August 2018: Measles cases reach record high in Europe
- 15 February 2019: Measles is evil. We have to vaccinate
- 25 March 2019: The measles has made my life
- 27 March 2019: US County declares measles outbreak emergency.
- 27 March 2019: Explaining the US measles outbreak
- 5 April 2019: Measles: How a preventable disease returned from the past
- 9 April 2019: New York measles emergency declared in Brooklyn
- 24 April 2019: Measles: Greater Manchester outbreak rises to 47 cases
- 26 April 2019: Measles outbreak: Trump tells Americans to “get their shots”
The sad reality is that this is a crisis that could largely have been prevented in the developed world. UNICEF reports that, globally, over the past 8 years an average of 21.1 million children have missed out on essential measles vaccines each year, giving a total of approximately 169 million unvaccinated children in that time period alone. In high-income countries, the statistics make for some sobering reading. The raw data over this time period is shown on the following table, courtesy of UNICEF.
The United States is significantly over-represented, as the equivalent doughnut chart shows below.
The reasons for failures to achieve required measles vaccination rates are varied. Measles has had a hard time because of the influence of disproven scare stories linking the MMR vaccine with autism. This misinformation has led to increasing fear or skepticism about the vaccine.
In low and middle-income countries, on the other hand, the causes are related to poor governance, poor health systems, complacency, logistic and economic challenges. Data from 2017 alone show that the countries that contributed the most were Nigeria, India, Pakistan, Indonesia and Ethiopia.
UNICEF highlights that two doses of the measles vaccine are essential to protect children from the disease. However, the global coverage of the first dose of the measles vaccine was reported at 85 per cent in 2017, a figure that has remained relatively constant over the last decade despite population growth. Global coverage for the second dose is much lower, at 67 per cent. The World Health Organization recommends a threshold of 95 per cent immunization coverage to achieve so-called ‘herd immunity’.
The BBC has a useful video that discusses vaccines, particularly the measles vaccine, in some detail. It is helpful to watch and is added below for reader convenience.