麻豆传媒

ATLANTA -- A 2017 mumps outbreak at a military facility mostly infected service members who had been immunized with the measles, mumps, and rubella (MMR) vaccine, a researcher said here.

Of the six cases of mumps from this outbreak, four of six had IgG titers that were seropositive, indicating they should have been immune to the disease, reported Lindsey Nielsen, PhD, of Brooke Army Medical Center, Fort Sam Houston, in San Antonio, Texas.

Laboratory PCR testing confirmed all six strains were Mumps Genotype G, which could suggest that the current MMR vaccine may not provide cross-protection against this particular strain of the disease, according to the at the ASM Microbe meeting.

Nielsen noted that many components of the MMR vaccine were developed back in the 1960s -- specifically, the mumps component is live attenuated Jeryl-Lynn strain genotype A -- but that "the strains circulating are not the strains circulating now."

"Some of the laboratory tests we do is based on science that is 30 or more years old. We have to make sure that's still relevant today, taking that into the context of clinical presentation," she told 麻豆传媒.

Researchers examined a mumps outbreak that occurred in a barrack of 252 service members. There were 11 service members evaluated for mumps, with six confirmed positive cases. The authors noted that of the 252 service members tested for mumps, 20.1% were mumps IgG seronegative, with seronegativity rates for rubella and measles at 24.4% and 28%, respectively.

They explained that on April 12, three patients reported to the emergency department for evaluation with "fever, swollen unilateral parotitis and malaise." Two of those three patients had elevated IgM mumps antibodies, which prompted an alert to public health officials and further screening with PCR testing.

On April 20, all 252 service members received a third dose of the MMR vaccine, following the Advisory Committee for Immunization Practices guidelines to give a third dose of vaccine during an outbreak.

But because members of the military are required to provide proof of vaccination and may provide "samples for titer determination" throughout their career, Nielsen and colleagues were able to examine serum samples stored in the Department of Defense Serum Repository to test prior samples of infected patients. There, they found that only two of six confirmed or probable cases had seronegative titers against mumps.

"If we looked at patient records and hadn't stepped back to think more broadly -- that it could be a failure of the test or a lack of cross-reactivity to the vaccine -- we would've discounted these people," she said.

Nielsen said that because the third dose of MMR vaccine did "slow the outbreak," it does argue that perhaps the third dose should be more of a standard rather than being given in response to an outbreak. But she also noted potentially broader issues with the MMR vaccine in general.

"Can [the MMR vaccine] provide cross-protection, how good is that cross-protection, and should we consider whether that is the best avenue for protection?" she said. "Maybe we need to reconsider our vaccination schedule or change the schedule to get more efficacy, or consider reformulation of the current vaccines we have on the market."

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