Mumps outbreak in Israel's highly vaccinated society: are two doses enough?
ABSTRACT Mumps outbreaks in recent years have given rise to questions about the effectiveness of the mumps vaccine. This study examined the epidemiological data from a recent mumps outbreak in Israel and from outbreaks in other countries with high vaccination coverage, and considered whether long-established vaccination policies designed to protect against mumps are in need of revision. Of over 5000 case patients in the Israeli outbreak, half of whom were in the Jerusalem health district, nearly 40% were aged ≥15 years and, of those whose vaccination status was known, 78% had been fully vaccinated for their age - features similar to those in recent mumps outbreaks in Europe and North America. The epidemiological and laboratory evidence suggests that many previously vaccinated adolescents and young adults are now susceptible to mumps because their vaccine-based immunity has waned. Booster vaccination programmes for those at high risk of infection during mumps outbreaks - particularly those in congregate living environments - merit priority consideration.
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ABSTRACT: Introduction In October 1988, routine immunisation against mumps was introduced in the United Kingdom as a combined measles, mumps, and rubella (MMR) vaccine for children aged 12-15 months. Although the incidence of mumps declined quickly, mathematical modelling supported the introduction of a second dose of MMR in 1996.1 In 1999, numbers of cases of mumps in teenagers in England and Wales began to rise. We report a further increase in the incidence of mumps in 2004. Participants, methods, and results Notifications of clinically diagnosed and laboratory confirmed mumps cases are collated for England and Wales by the Health Protection Agency Centre for Infections. Confirmed cases include those obtained by routine follow-up of all notified cases where IgM is detected in oral fluid. In 2004, the number of mumps notifications in England and Wales increased to 16 436 from 4204 in 2003. A total of 8104 cases of mumps were confirmed in 2004, compared with a total of 3907 cases in the previous five years. All regions reported more cases in 2004 than in 2003. Cases were predominantly in older teenagers and young adults born before 1987 (figure), and most were in those born between 1983 and 1986. Many of this group are currently at tertiary level education institutions and are associated with outbreaks in universities and colleges across England and Wales. Outbreaks in the same birth cohorts have also been reported in military establishments and prisons.2 Only 2.4% (197/8104) of confirmed cases in 2004 occurred in children who would have been offered two doses routinely—that is, those born between 1993 and 1999 (figure); only 29 of these had documented receipt of two doses of MMR. Only 62 cases (0.8%) have been confirmed in children born after 1999. View larger version:In a new windowDownload as PowerPoint SlideConfirmed cases of mumps in 2004 by year of birth (1970-2001) per 100 000 population and opportunity for MMR vaccination (excludes 105 cases of unknown birth year, 351 born in 1914-69, and 30 born after 2001) Comment During 2004, numbers of notifications and confirmed cases of mumps increased dramatically in all regions across England and Wales, after several years of moderately increased incidence. Most cases are in young adults born before 1988, who would not have been routinely scheduled for MMR during childhood. The highest attack rate was in those born between 1983 and 1986, who were too old to be offered MMR vaccination routinely when it was introduced in 1988, although some may have received one dose of MMR as part of a catch-up programme offered at school entry.3 These individuals would have missed the opportunity for mumps exposure during childhood because high coverage in younger children had reduced circulation of mumps in the UK. Older individuals are more likely to have had mumps when it was still a common childhood infection. The absence of cases in children in younger cohorts, including those affected by the fall in MMR coverage since 1995,4 confirms the effectiveness of the current vaccination policy. What is already known about this topic The incidence of mumps fell after the MMR was introduced in 1988 The number of confirmed mumps cases in 2004 has risen across England and Wales, with a number of reported outbreaks in universities What this study adds The current mumps outbreak has been predominantly in older teenagers and young adults, who would not have been offered two doses of MMR This confirms the effectiveness of the current vaccination policy The mumps component of the MMR vaccine used in the UK is believed to offer around 90% protection for one dose, although recent reports indicate that this could be as low as 64%.5 This outbreak confirms that the current, two dose MMR schedule is effective in preventing mumps. In addition to improving routine coverage of MMR, reviewing the vaccination status of all school leavers is recommended, to ensure that they have received two doses of MMR. Other opportunities to offer MMR vaccine to the age group at highest risk, such as when entering university or other institutions, should also be considered. See also p 1120, and Clinical review p 1132 Footnotes Contributors ES, MR, and JW conceived and designed the study. ES conducted the epidemiological analyses. SB, HL, RH, and DB interpreted laboratory data. All authors critically reviewed and contributed to the final draft of the paper. MR is guarantor. Funding None. Competing interests DB's laboratory has received funding from vaccine manufacturers for specific projects. He has acted as an unpaid expert witness in MMR litigation for vaccine companies. All other authors have nothing to declare. References1.↵Gay NJ, Miller E, Hesketh L, Morgan-Capner P, Ramsay M, Cohen B, et al.Mumps surveillance in England and Wales supports introduction of two dose vaccination schedule.Commun Dis Rep CDR Rev1997; 7(2):R21–6.OpenUrlMedline2.↵Communicable Disease Surveillance Centre.Laboratory confirmed cases of measles, mumps and rubella, England and Wales: July to September 2002.Commun Dis Rep CDR Wkly2002; 12(48).3.↵Gay NJ, Valambia S, Galasko D, Miller E.Selective rubella vaccination programmes: a survey of districts in England and Wales.Commun Dis Rep CDR Rev1994; 4(7):R77–9.OpenUrlMedline4.↵Communicable Disease Surveillance Centre.Fall in MMR vaccine coverage reported as further evidence of vaccine safety is published.Commun Dis Rep CDR Wkly1999; 9(26): 227,230.5.↵Harling R, White JM, Ramsay ME, MacSween K, van den Bosch C.The effectiveness of the mumps component of the MMR vaccine: a case control study.Vaccine2005 (in press).BMJ (Clinical research ed.). 06/2005; 330(7500):1119-20.
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ABSTRACT: Mumps epidemics in Canada and the United States prompted us to review evidence for the effectiveness of 5 different vaccine strains. Early trials with the Jeryl Lynn vaccine strain demonstrated an efficacy of approximately 95%, but in epidemic conditions, the effectiveness has been as low as 62%; this is still considerably better than the effectiveness of another safe strain, Rubini (which has an effectiveness of close to 0% in epidemic conditions). The Urabe vaccine strain has an effectiveness of 54%-87% but is prone to cause aseptic meningitis. Little epidemiological information is available for other vaccines. The Leningrad-Zagreb vaccine strain, which is widely used in developing countries and costs a fraction of what vaccines cost in the developed world, seems to have encouraging results; in 1 study, the effectiveness of this vaccine exceeded 95%. Aseptic meningitis has also been reported in association with this vaccine, but the benign nature of the associated meningitis was shown recently in Croatia. Also, the Leningrad-3 strain seems to be effective but causes less-benign meningitis. No mumps vaccine equals the best vaccines in quality, but the virtually complete safety of some strains may not offset their low effectiveness. Epidemiological data are pivotal in mumps, because serological testing is subject to many interpretation problems.Clinical Infectious Diseases 09/2007; 45(4):459-66. · 9.37 Impact Factor
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ABSTRACT: In 2006 the United States experienced the largest nationwide mumps epidemic in 20 years, primarily affecting college dormitory residents. Unexpected elements of the outbreak included very abrupt time course (75% of cases occurred within 90 days), geographic focality (85% of cases occurred in eight rural Midwestern states), rapid upward and downward shift in peak age-specific attack rate (5-9-year olds to 18-24-year olds, then back), and two-dose vaccine failure (63% of case-patients had received two doses). To construct a historical context in which to understand the recent outbreak, we reviewed US mumps surveillance data, vaccination coverage estimates, and relevant peer-reviewed literature for the period 1917-2008. Many of the unexpected features of the 2006 mumps outbreak had been reported several times previously in the US, e.g., the 1986-1987 mumps resurgence had extremely abrupt onset, rural geographic focality, and an upward-then-downward age shift. Evidence suggested recurrent mumps outbreak patterns were attributable to accumulation of susceptibles in dispersed situations where the risk of endemic disease exposure was low and were triggered when this susceptible population was brought together in crowded living conditions. The 2006 epidemic followed this pattern, with two unique variations: it was preceded by a period of very high vaccination rates and very low disease incidence and was characterized by two-dose failure rates among adults vaccinated in childhood. Data from the past 80 years suggest that preventing future mumps epidemics will depend on innovative measures to detect and eliminate build-up of susceptibles among highly vaccinated populations.Vaccine 10/2009; 27(44):6186-95. · 3.77 Impact Factor