Just a small decline in childhood measles vaccination levels can produce disproportionate negative effects both to public health and the economy, new research has revealed.
Vaccines save lives. But in some regions across the US vaccination rates are declining due to bad information and poor choices, and now scientists have put together data on how badly these choices can affect us all.
A team from Stanford University and Baylor College of Medicine looked into the public health and economic impact of vaccine hesitancy, "defined as a delay or refusal to accept vaccination based on personal beliefs despite availability."
In other words, they ran the numbers on what even a handful of anti-vaxxers can cost the public, and those numbers ain't pretty.
Using the combined measles, mumps, and rubella (MMR) vaccine and the measles virus as a case example, the researchers built a computer model to estimate thousands scenarios of increased vaccine hesitancy, and how that would affect hypothetical measles outbreaks.
"We focussed on measles as a case example of the effects of declining vaccine coverage because it is highly infectious," says lead researcher Nathan Lo from Stanford University.
"It's likely to be the first infectious disease causing outbreaks if vaccination declines."
The team's data indicates that just a small 5 percent drop in MMR vaccine coverage of children aged 2-11 would result in a tripling of annual measles cases in this age group, from the current 48 cases per year to a whopping 150.
Now that may not sound like a lot of sick children, but measles is a rashy, insanely contagious illness that can cause serious or even fatal complications. It is still one of the leading global causes of death in children, mostly happening in developing parts of the world without adequate vaccine coverage.
Before we had a way to prevent measles through vaccination, millions of children died every year, a devastating number that has been steadily decreasing.
"During 2000-2015, measles vaccination prevented an estimated 20.3 million deaths," reports the World Health Organisation.
The reason overall vaccination levels are so important is because of the way vaccines prevent disease. There's always a small part of the population that can't be vaccinated for medical reasons (for example, kids with a compromised immune system), or are too young (babies can only get the first dose of MMR vaccine when they're one year old). All of them are super-vulnerable to rogue viruses.
These days in the US most measles cases occur when people have been travelling abroad and unwittingly bring the disease back. An infected person then becomes a disease vector, spreading it to anyone who isn't protected.
In an ideal situation, 90-95 percent of people would be vaccinated, and the virus is unable to take hold. Which makes that small group who is unable to be vaccinated entirely dependent on everyone around them, a principle called 'herd immunity'.
That's why it's so crucial that people don't opt out of vaccination - they are not just making a personal choice, but instead affecting their community as a whole. And because vaccine hesitant parents tend to live in clusters, it makes the potential of large outbreaks that much more likely.
Just this year, the Somali-American community in Minnesota experienced an outbreak of the deadly disease which surpassed all last year's US cases taken together.
And it's not just the public health argument alone. The Stanford-led team also ran some numbers on how much a drop in MMR vaccination coverage would cost in monetary terms.
At a conservative estimate, that same 5 percent drop in vaccination could cause an additional US$2.1 million expense for the public health sector. And the researchers note that this doesn't even include personal costs to families, loss of productivity to the parents, hospitalisation costs and other possible economic impacts.
"I think our study is a wake-up call for what we can expect in the coming months and years as vaccine coverage rates continue to decline in the 18 states that now allow non-medical or philosophical belief exemptions," says senior researcher Peter Hotez from Baylor College of Medicine.
The team hopes that their findings are going to play a role in policy making across the US.
"These findings should play a key role in any policies adopted by state or national governments that relate to childhood vaccination," they write in the study.
The research is available open-access in JAMA Pediatrics.