Mumps is back in the US, and people are most likely getting sick because the effects of the vaccine they got in early childhood are wearing off, new research suggests.
For three decades after mumps vaccines were introduced in 1967, the illness all but disappeared from the US.
But, starting in 2006, outbreaks have been getting bigger, and occurring more closely together.
Already this year, there have been 304 cases of mumps in the US and 122 cases have been confirmed in the UK.
Researchers from Harvard University found that the resurgence has likely become possible because immunity given by the mumps vaccine is wearing off, and are calling for the introduction of a third booster shot to be given at age 18 in order to cut risks of outbreaks like this year’s.
Harvard researchers found that the mumps vaccine wears off within 19 years of the second shot for 50 percent of people who get it and recommend an additional booster shot
Mumps is an extremely contagious viral illness that affects the salivary glands.
It causes fever, headaches loss of appetite and is recognizable for the puffiness it causes in the cheeks of people sick with the infection.
Mumps can lead to meningitis, brain swelling and deafness and is far more dangerous for children, who are also much more prone to infection.
As recently as 2003, 28 percent of children under five who got the mumps had to be hospitalized, according to the Centers for Disease Control and Prevention.
Complications from the infection for adults can include infertility-causing testicular inflammation, meningitis and deafness.
But until recently, mumps was considered to be more or less a problem of the past.
The introduction of the mumps shot in the 1960s decreased annual cases of the once-deadly illness by 99 percent, according to the Centers for Disease Control and Prevention.
Vaccination against mumps, measles and rubella (MMR) became part of routine check-ups, being given to children between 12 and 15 months.
For 20 years, that one-time shot was thought to be sufficient to protect people for a lifetime.
But the 1980s brought more outbreaks and health experts tacked another MMR shot – to be given between ages four and five – onto their recommendations.
Once again, the US thought that it had eradicated the disease for the long haul, and once again, that notion was proven wrong.
In 2006, outbreaks began again to pepper the US, concentrated around college campuses, prisons and close-knit communities where the virus could spread quickly among large groups in close quarters.
Some have blamed contemporary anti-vaccination movements for the resurgence, but the new study’s findings show that, even if just as many people are getting the shot, it simply does not last forever.
For a quarter of Americans who got the MMR shot, the researchers estimated that its effects wore off within just eight years.
Half of vaccinated people were no longer protected from mumps within 19 years, and a full 75 percent were once again vulnerable to the disease 38 years later.
‘This analysis helps address a persistent question surrounding the recent mumps outbreaks, pointing to the key role played by waning vaccine induced immunity, and helps frame the research and policy questions on how best to control mumps,’ said study co-author Dr Yonatan Grad.
‘Vaccination is the centerpiece of current public health strategy against mumps,’ said his co-author, Dr Joseph Lewnard.
‘Knowing that protection wanes in the long term can help inform how we deploy vaccines to prevent or contain future outbreaks,’ he added.
In light of their findings, the Harvard scientists are now urging that a second booster shot, administered at age 18, should become the norm in order to prevent further future mumps outbreaks.