Mumps outbreaks are becoming increasingly common among vaccinated communities despite years of plummeting rates.
Before the vaccine, the virus of the salivary gland, spread by saliva or mucus through coughing and sneezing, was a common infection among children, and led to hundreds of deaths.
The rate of infection plummeted down to a couple of hundred a year by the 1980s and continued that way until around 2010.
But last year, the CDC recorded more than 6,000 mumps infections, particularly driven by clusters of outbreaks, many of which are on college campuses and sports teams.
Experts warn that this is driven by two key factors. First, exchange of bodily fluids through drinks or contact among close-knit groups such as students and athletes. Second, a waning sense of urgency to vaccinate children against the now-distant threat of mumps which plagued baby boomers and the silent generation.
The CDC did not collect data on mumps infections until 1968, when after the mumps vaccine was brought in. The rate of infection plummeted down to a couple of hundred a year by the 1980s and continued that way until around 2010
A mumps vaccine was rolled out in the US in 1967, after which rates of mumps infections and mumps-related deaths dropped.
Four years later, the MMR (mumps-measles-rubella) vaccine was released, triggering another drop, which continued, albeit with a few bumps in the road, until 2010-13.
For decades, the CDC has advised children get two doses of the MMR vaccine – their first at around one year old, and their second between four and six years old – which gives a child about 88 percent protection against mumps, measles and rubella.
‘That’s high but not 100 percent,’ warns Dr Pritish Tosh, MD, an infectious diseases specialist at the Mayo Clinic told Daily Mail Online.
According to Dr Tosh, the strength of the vaccine also relies on ‘herd immunity’, requiring that the vast majority of each community (at least 90 percent) is protected.
‘When you have some people who are unvaccinated or under vaccinated in a community then we lose some of that herd immunity meaning the populations can be at-risk of infection, even if they were vaccinated.
‘Once you start dropping in that number, you run a risk of re-introducing mumps into a population.
‘Certainly, unvaccinated people get sick but also there will likely be vaccinated people who get sick because the vaccine is not 100 percent effective.’
He warns: ‘The unvaccinated people are amplifying the outbreak then allowing some who are unvaccinated to become sick. This has been seen more and more including in college campuses.’
In the case of outbreaks on campuses, as with the current outbreak at Syracuse University in New York, health officials tend to administer a third dose of the vaccine – but that is only permitted in cases of an outbreak.
According to Dr Tosh, the only preventative measure we can take is to remind people of the days when mumps was a genuine thread.
‘You see in communities born before the 1960s, they had a very good vaccination rate because they had seen what mumps can do to a child.
‘Now, on college campuses, you’re seeing people who were not getting the vaccine voluntarily. Also people from all over the world come to colleges, who may not be vaccinated.’
But most importantly, he says, ‘we have lost our community memory for what those diseases do.
Fifty years ago, mumps was a fairly common infection among babies that led to many deaths
‘The most common cause of central neural hearing loss used to be mumps. Hundreds of children would die each year from mumps in the United States. Congenital rubella syndrome which would cause those deformities in children.
‘We’ve forgotten about all that.
‘Because the vaccines have been so successful in stopping what those diseases do, people have started to opt out.’
Despite being a staunch advocate for vaccines, he concedes he understands anti-vaxxers’ concerns.
‘I try not to blame the parents,’ he says. ‘I understand the fear for them as a parent. I get it. There’s not an ongoing outbreaks of those diseases, it’s not an immediate threat, and they are hearing rumors about dangers of the vaccine.
‘The risk of getting measles in the US is currently low because of vaccinations, but the parents’ chances of being ostracized from their social group is high.
‘But this is leading to what we are seeing now: outbreaks.’