Elsevier

Vaccine

Volume 29, Issue 45, 19 October 2011, Pages 8024-8031
Vaccine

MMR vaccine effectiveness in an outbreak that involved day-care and primary schools

https://doi.org/10.1016/j.vaccine.2011.08.056Get rights and content

Abstract

Objective

In 2006, a large measles outbreak occurred in Catalonia (Spain), where the immunization schedule included two doses of MMR vaccine at 15 months and 4 years. The aim of this study was to investigate the vaccine effectiveness (VE) of MMR in children attending day-care and pre-school centres and to estimate the number of cases that would have been avoided by administering the first dose of MMR at 12 months.

Methods

A retrospective cohort study was carried out between October 2006 and January 2007 in day-care and pre-school centres with confirmed measles cases. VE was calculated in children aged ≥15 months without previous measles infection. Cases avoided by advancing the first dose of MMR to 12 months were estimated by calculating the basic and effective reproduction number in centres where transmission outside the class was observed.

Results

Fifteen centres and 1394 children were included. There were 77 confirmed cases (attack rate = 5.5%). Vaccination coverage of the 1121 children aged ≥15 months was 91.6% and VE was 96% (95%CI 89–98%).

There were 33 (41%) cases in the 81 children aged 12–14 months. Advancing the first dose to 12 months would have prevented 74 cases (91.5%) and lowered the attack rate from 41% to 8.6%.

Conclusions

Over 90% of cases in children aged 12–14 months would have been avoided by MMR administration at 12 rather than 15 months. We strongly recommend advancing the first dose of MMR to 12 months in order to reduce the risk of measles outbreaks.

Highlights

► We studied a large measles outbreak in day-care and pre-school centres. ► The immunization schedule included two doses of MMR vaccine at 15 months and 4 years. ► Attack rate in children aged 6–11 months was higher than 12–23 months (22% and 9%). ► Vaccine effectiveness after receiving at least 1 dose of MMR vaccine was high (>96%). ► Advancing the first dose to 12 months instead of 15 would have prevented 91% of cases.

Introduction

Measles, a disease caused by a Morbillivirus of the paramyxovirus family, is one of the most contagious human infectious diseases, with a basic reproduction number (R0) of 15–18 [1], [2]. The worldwide disease burden is high, with the case fatality rate estimated at approximately one death per 1000 cases [3], [4], [5]. In 2009, there were 222,408 cases worldwide [6].

Given the availability of a highly-effective vaccine, highly-specific and sensitive diagnostic tests and the lack of animal reservoirs, some regions have adopted elimination targets. In the Americas, the 1994 Pan American Sanitary Conference established the goal of eliminating measles from the Americas, and the number of cases of measles was reduced by 99% in 1996 in comparison to 1990 levels [7]. Currently, measles is no longer endemic in the Americas and most countries have interrupted transmission of the virus [8].

The European Region of the World Health Organization set a goal of eliminating indigenous measles in the Region by 2010, but due to the increase of cases and outbreaks in the central and western parts of the Region, this goal has been postponed to 2015 [9]. Finland, where the coverage with two doses of vaccine was 95%, eliminated measles in 1993 [10]. However, as vaccination coverage with two doses is still suboptimal in some countries and population groups, the virus still circulates widely in Europe [11].

During the period 2005–2008, 120 outbreaks were reported in Europe, of which 17 reported more than 250 cases, with 25 deaths occurring [12].

In Catalonia, a region in north-eastern Spain with over seven million inhabitants, there was an outbreak of measles involving 381 cases between August 2006 and July 2007 due to a case imported from Bosnia [13]. The previous epidemic wave occurred in 1995, when 1860 cases were reported [14]. After this, cases appeared intermittently and irregularly, and between 2000 and 2005 there were only 25 cases reported (0.06/100,000 persons-year), due to high vaccination coverages. In 2006–2007, the incidence rate was 3.1/100,000 persons-year. The outbreak occurred mainly in the Barcelona-South Health Region, with a rate of 9.2/100,000 persons-year, and the majority of cases occurred in children aged less than 15 months. Seventy-nine percent of the cases occurred between October 2006 and January 2007.

The measles vaccine was introduced in 1978 in the publicly-funded vaccination schedule of Catalonia, for children at the age of 12 months. In 1980, the measles vaccine was replaced by a single dose of the combined measles, mumps and rubella vaccine (MMR) at 12 months. In 1987, the age of MMR administration was changed from 12 to 15 months, and in 1988 a second dose of MMR at 11 years was added. To ensure that the proportion of vaccinated children aged less than 10 years reached 95% and to achieve the elimination of measles by 2000, from the last quarter of 1998, the second dose of MMR was advanced to 4 years [15]. Therefore, at the time of the outbreak studied here, routine vaccination consisted of two doses of MMR at 15 months and 4 years, using the Schwarz (Priorix®) and Enders (MSD®) strains.

At the end of January 2007, to control the outbreak, in addition to post-exposure prophylaxis measures in the home and educational centres where cases appeared, a mass vaccination campaign was carried out consisting of the administration of one dose of MMR in children aged 9 to 12 months, with a second dose at 15 months.

The objective of this study was to evaluate the direct, indirect and total effectiveness of the measles component of the MMR vaccine in the context of a measles outbreak that affected mainly children attending day-care and pre-school centres and to estimate the number of cases that would have been avoided if the first dose of MMR vaccine had been administered at 12 rather than 15 months.

Section snippets

Study population

We carried out a retrospective cohort study in educational centres in the Barcelona-South Health Region (population 2,853,658) attended by a confirmed case of measles during his infectiousness period with rash onset between 1st October 2006 and 15th January 2007. The temporal distribution of all cases of the outbreak is shown in Fig. 1. The study cut-off was established as 15 January 2007, in order to avoid possible bias due to the mass vaccination campaign. Centres where MMR administration

Characteristics of the study population

During the study period, we investigated 15 centres (12 day-care [0–3 years] and 3 pre-school [3–6 years] centres) with a total of 1394 children, of whom 51% (706) were male and with a median age of 27.3 months (range: 3.5–70.3). The characteristics of the centres investigated are shown in Table 1.

The vaccination status was determined in 1334 children (96%). The proportion of vaccinated children was 73.8% (range; 45.7–100%). Vaccination coverage was 91.6% in children aged ≥15 months (1121),

Discussion

This outbreak illustrates the current epidemiology of measles in Spain where, thanks to high MMR vaccine coverage, there is no endemic measles transmission, but there is a risk of outbreaks due to imported cases, as shown by the outbreak referred here, which was due to an imported case that generated small clusters of short duration in unvaccinated people. The difficulty in implementing adequate infection control measures in less than 72 h outside the family environment may have contributed to

Conclusions

Direct vaccine effectiveness after receiving at least 1 dose of MMR vaccine was high (>96%). However, the outbreak could not be avoided due to the large number of exposed children who had not reached the recommended vaccination age. It is important to monitor the changes in the fraction of susceptible individuals over time.

If the first dose of MMR vaccine had been administered at 12 instead of 15 months, 91.5% of cases in children aged 12 to 14 months would have been avoided. In order to

Acknowledgements

This work was partially funded by CIBER Epidemiología y Salud Pública (CIBERESP) Spain, FEDER and AGAUR (expedient number 2009 SGR 42).

We thank the reporting physicians and the staff and parents of the day-care and primary schools.

Conflict of interest statement: None declared.

References (45)

  • Word Health Organization. WHO vaccine-preventable diseases: monitoring system. 2010 global summary. WHO: Immunization,...
  • Pan American Health Organization

    Measles elimination by the year 2000

    EPI Newslett

    (1994)
  • C.A. De Quadros

    Can measles be eradicated globally?

    Bull World Health Organ

    (2004)
  • Word Health Organization. Eliminating measles and rubella and preventing congenital rubella infection. WHO European...
  • H. Peltola et al.

    The elimination of indigenous measles, mumps and rubella from Finland by a 12 years, two dose vaccination program

    N Engl J Med

    (1994)
  • R. Martin et al.

    Progress toward measles elimination-European region, 2005–2008

    MMWR

    (2009)
  • A. Domínguez et al.

    Large measles outbreak in a community with high vaccination coverage

    Clin Infect Dis

    (2008)
  • Departament de Sanitat i Segueretat and Social

    L’eliminació del xarampió a Catalunya per l’any 2000

    (1991)
  • I. Barrabeig et al.

    Effectiveness of measles vaccination for control of exposed children

    Pediatr Infect Dis J

    (2011)
  • WHO. Surveillance guidelines for measles, rubella and congenital rubella syndrome in the WHO European Region....
  • W. Orenstein et al.

    Field evaluation of vaccine efficacy

    Bull World Health Organ

    (1985)
  • M.E. Halloran et al.

    Direct and indirect effects in vaccine efficacy and effectiveness

    Am J Epidemiol

    (1991)
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