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Letters

Measles data are reliable

BMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7008.810 (Published 23 September 1995) Cite this as: BMJ 1995;311:810
  1. Mary Ramsay,
  2. David Brown
  1. Consultant epidemiologist Immunisation Division, PHLS Communicable Disease Surveillance Centre, London NW9 5EQ
  2. Consultant virologist Enteric and Respiratory Virus Laboratory, PHLS Virus Reference Division, London NW9 5EQ

    EDITOR,--Nigel Higson claims that the only source of data on measles cases which has remained consistent before and after the measles-rubella campaign is statutory notification and that numbers of notified cases have shown little decline.1 As he admits, numbers of notifications are less reliable than cases confirmed by saliva testing, but this service was not widely available before the campaign. The saliva assay, however, was extensively piloted in 18 districts of the United Kingdom between October 1991 and October 1994.2 3 During this pilot 36-38% of patients with measles tested were IgM positive,2 3 suggesting recent infection, compared to only 4% of patients tested since the campaign. Since November 1994, saliva samples have been received in over 50% of notified cases and the proportion that is IgM positive has fallen with time (table).

    Saliva tests performed in notified measles cases from England and Wales

    View this table:

    In addition, measles cases confirmed by serology, isolation, or antigen detection have been reported to the Communicable Disease Surveillance Centre by laboratories in England and Wales for over 20 years. Unlike notifications, the number of laboratory reports has fallen dramatically, from 224 cases reported with sample dates between 1 January and 31 May in 1994 compared with only 52 in the same period of 1995. Many of the 1995 cases occurred during late 1994 and early 1995, when the full effect of the campaign had not been felt--only four cases have been reported with sample dates during May 1995.

    Both data sources clearly indicate that measles transmission has been substantially reduced by the vaccination campaign, in particular in 5-16 year olds--the age group targeted.4 Small numbers of measles cases are still being confirmed in preschool children and unvaccinated adults, and at least four recent infections seem to have been contracted abroad. A comprehensive surveillance programme for measles is now established and will allow us to monitor the longer term effects of the measles-rubella campaign and to define future vaccination policy in England and Wales.

    References

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