Rise in mumps cases linked to waning immunity given by MMR vaccine

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Public Health England says waning immunity may be contributing to transmission after 948 cases of mumps in first quarter of 2013.

Rise in mumps cases linked to waning immunity given by MMR vaccine

Public health officials are warning of a rise in cases of mumps due in part to waning immunity to the disease in those given the MMR vaccine.

There were 948 cases of mumps in the first quarter of the year, more than the 673 measles cases which prompted a national catch-up campaign to increase take-up of the MMR vaccine. Half of those who developed mumps in the first three months of this year had received at least one of the two jabs needed to give them the best chance of not falling ill.

Public Health England’s (PHE) official weekly update for professionals on infectious diseases stated in June that “some waning immunity may be contributing to transmission”.

Health experts are anxious that falling immunity to the mumps element of the MMR vaccine must not undermine the message that it still improves young people’s chances of not getting mumps – as well as protecting against measles and rubella.

Mary Ramsay, head of immunisation at PHE, said: “We think that in conditions of high exposure and close mixing [mumps] infection can spread even if vaccinated – but this makes it even more important for the unvaccinated to have the vaccine because herd immunity is not high, so individual protection relies on your own vaccination.”

She pointed to research, in which she was involved, on the 2004-5 mumps outbreak that suggested even one jab cut the risk of hospital treatment, painful swelling of the testicles for young men and meningitis.

National and local efforts to improve MMR coverage have been organised in recent years to make up for fall-off due to the now discredited link between MMR and autism. These included vaccination sessions at universities and colleges which were hit by big mumps outbreaks in 2004-5 – but there remains an estimated 1 million children and young people who have not had both jabs.

The MMR was phased in for children aged a year to 15 months from 1988, with a second dose added to the childhood vaccination programme at three years and four months in 1996. Before the MMR vaccine was introduced in 1988, there was no routine immunisation against mumps in the UK, and an immunisation campaign in 1994 to head off a measles epidemic used only a combined measles and rubella vaccine because there was not enough MMR.

Government advisers on vaccination have been monitoring the mumps part of the vaccine for some time. In January last year they noted that “a significant proportion” of infections were occurring in young people who had had jabs and that “it may be reasonable to assume that protection from infection falls to around 60% after 10-15-years.” A subcommittee of the Joint Committee on Vaccination and Immunisation looked at a number of options. But moving the second MMR dose from three-year-olds to an older age would leave young children unprotected against measles and rubella, they concluded, while a third dose of MMR during adolescence might not be cost-effective since the effectiveness of another jab for those already with immunity was uncertain.

There would also be “very little added protection” against measles and rubella and it might only shift the burden of the disease due to “waning vaccine-induced” immunity to older age groups. The advisers could not offer any advice on whether booster doses would work during outbreaks because evidence was so limited. The best solution was to reinforce current policy on encouraging families of un- or undervaccinated children to put that right.

Public Health England would like to see NHS advice on the MMR vaccine changed to reflect the issue of waning immunity to the mumps element of the vaccine.

Source:
The Guardian

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