A report by the World Health Organization (WHO) and Unicef warns that there could be a significant increase in the number of measles cases around the world. More than 17,000 cases have already been reported globally in January and February, an increase of nearly 80% from the 9,665 cases reported in the same period last year. The report cites low global vaccination rates in the past few years as the main driver of this increase. Given measles is a preventable disease, it's worrying to see cases rising.
Measles is a disease caused by infection by the measles virus, which is spread through respiratory droplets when a person with the virus coughs or sneezes. Symptoms can include fever, cough, red eyes and a rash. Measles is extremely contagious, and is one of the most easily spread viruses that infect humans. It is particularly dangerous for children, who may develop severe complications (such as pneumonia or brain swelling) as a result of measles.
But measles is easily prevented with a double vaccine dose which is usually administered by the time a child is four years old. This vaccine provides lifelong protection against measles. In places where measles vaccination is high, there are low numbers of infections and deaths. Despite this, cases of measles are still seen in nearly every country in the world.
According to the report, cases are rising most quickly in countries where vaccination rates are the lowest in the world. The countries that experienced the most significant increases in case numbers last year were Somalia, Yemen, Afghanistan, Nigeria and Ethiopia. In these countries, only 46-68% of the population is vaccinated against measles. Typically, it's recommended that 95% of the population needs to be vaccinated to protect children.
The low vaccination rates in many of these countries are likely caused by a number of factors - including low investment in healthcare systems as well as conflicts and natural disasters that disrupt vaccination programmes. But the pandemic has only worsened measles vaccine rollout, due to such health programmes being halted and greater funding and effort being diverted to COVID-19 vaccination programmes. This means many children didn't receive their first or second doses of the measles vaccine during the pandemic - making it even more difficult to reduce outbreaks and stop the spread of this virus.
Other reasons - such as ongoing conflicts and refugee migrations - also make it difficult to track patients and administer double doses on time. With a contagious disease like measles, these can spread rapidly in crowded camps and houses, making immunisation even more important.
Global cases rising
The WHO reports also show that case numbers are rising in almost all countries around the world - the UK included.
In 2019, 119 of the 194 WHO member states had over 90% first dose vaccination coverage. In 2020, this dropped to only 75 countries with the largest decreases seen in the Netherlands, Armenia and Romania. In the UK alone, only around 87% of people are fully vaccinated against measles - though this number varies depending on the region, with some areas such as London only having a vaccination rate of around 75%. It's a similar story in the US, where case numbers are increasing despite measles being declared eliminated in 2000.
Again, it's likely that the rise in cases many countries have seen is because fewer vaccines are being administered. While the pandemic is one reason for this, vaccine hesitancy is another factor. A direct relationship has been observed between increased hesitancy and increased cases of measles.
Children and pregnant people are at greatest risk from these increases in measles cases. This is because they're more likely to suffer severe side effects as a result of measles. But anyone who isn't vaccinated is at risk of contracting the disease - and more importantly, they're more likely to pass it on to any other unvaccinated people they come into contact with.
Mass vaccination programmes are still the best way to combat the rise in measles cases globally - especially given 95% of the population needs to be vaccinated with both doses to achieve herd immunity. While ensuring these programmes have the funding needed to provide these vaccines is important, it may also be important to put efforts into educating people on the importance of measles vaccination and that the vaccine is safe.
Global support must also be given to countries experiencing low vaccination rates - especially if this is due to natural disasters or refugee crises. This is especially important given that measles is highly contagious and local outbreaks can quickly spread globally.
Given the increase in case numbers seen at the beginning of this year, it's likely numbers will only continue to rise throughout 2022. This resurgence is just one example of the knock-on effect that the COVID-19 pandemic has had on other diseases - and the importance of getting regular vaccination programmes back on track to prevent further spread of harmful viruses.
Author: Conor Meehan - Senior Lecturer in Microbiology, Nottingham Trent University