This fall, a major mumps outbreak occurred in Anchorage. The first case was reported in May 2017, and the number of affected citizens has grown over the past several months. On Nov. 15, the Department of Health and Social Services published an update on the outbreak along with recommendations for the prevention of the disease.
As of Dec. 2, 71 confirmed and 15 probable cases have been identified in Alaska. Since all confirmed and probable cases were either residents of or spent extensive time in Anchorage, the outbreak has been limited to the city so far.
It is the largest outbreak Alaska has experienced since the mid 1970s.
Mumps is commonly referred to as a childhood disease. This term, however, can be misleading since other age groups can be infected by the virus as well. The median age among the 44 confirmed patients is 24 years.
Even though mumps is considered a vaccine-preventable disease, about half of the confirmed cases received at least one dose of the measles, mumps and rubella vaccine (MMR).
Being vaccinated against mumps does not necessarily mean that one is completely immune to the disease, Dr. Joe McLaughlin, the Alaska state epidemiologist, said.
“The MMR vaccine confers immunity in about 78 percent of people after they get one dose of the vaccine and in 88 percent of the people who get two doses of the vaccine. So that means that 12 percent of people who get two doses of the MMR vaccine will still be susceptible to mumps,” McLaughlin said.
Not only does the number of vaccine doses a person receives influences a person’s immunity, the timing of the vaccinations is a critical factor, too. After getting the MMR vaccine, the immunity to mumps tends to wane over time.
“If you got your two MMR shots when you were a year old, and when you were five years old and you haven’t been exposed to mumps since then, your immune system hasn’t had the opportunity to recall that particular antigen,” McLaughlin said. “So there’s a chance that you may not be immune to mumps currently.”
At the moment, the national recommendation for children is to get one dose of the vaccine when they are between 12 and 15 months of age and their second dose between 4 and 6 years of age. Under special circumstances, the recommendations have now changed.
“This year, for the first time ever, the Advisory Committee on Immunization Practices [ACIP] has recommended a third dose or a booster dose of vaccine in outbreak settings to high-risk groups,” McLaughlin said. “In our particular outbreak, we know that over 80 percent of the cases have been in the Native Hawaiian or other Pacific Islander population here in Anchorage.”
While the original source of the outbreak is uncertain, there is a possible connection between a Pacific island and the transmission of the virus to Anchorage residents.
Several of the initial patients reported recent travel to or close contact with a person who had recently visited a Pacific island where mumps is circulating.
“For people who do come down with the mumps, our strong recommendation is that as soon as they think they might have mumps, to stay home from school or college or work as well,” McLaughlin said. “We want them to stay home at least five days after the onset of parotitis, which is the swelling of the cheeks.”
During these five days, people affected by the virus are most infectious.
The majority of higher education institutions in the U.S. require their students to get at least some vaccinations based on the current scientific knowledge. Generally, immunizations are not mandatory for the majority of the UAA student body.
However, there are some exceptions to this arrangement as Rhonda Johnson, a UAA health sciences professor, said.
“Some students, such as those training to be clinical providers, or working or traveling in high risk situations may be required to take additional vaccinations,” Johnson said.
Even though the effectiveness of vaccination has been verified scientifically, many parents still choose not to immunize their children.
“I think there is often incomplete understanding of the overall risks and benefits of immunizations,” Johnson said. “In some ways, the success of vaccination programs in controlling infectious diseases in the last century has led to both unfamiliarity with the devastating impacts of some diseases and unwarranted complacency about the real risks of infections in a global community.”
The two-dose series of the MMR vaccine is provided at no cost to all Alaskans aged 18 years and younger. A limited supply of MMR vaccine is available free of charge for uninsured adults aged 19 years and older at the Municipality of Anchorage, Department of Health and Human Services.