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Adverse effects of mass vaccination in Brazil: the case of MMR

Mass vaccination is one of the best tools for controlling diseases. However, sometimes vaccines can themselves be the cause of adverse effects that undermine public trust. In Brazil, the implementation of mass child vaccination campaigns against measles, mumps and rubella (MMR) took place even though there was evidence that contradicted previous knowledge about the safety of the vaccine strain used. Experience here suggests that an effective safety monitoring system must be applied to any mass immunisation programme.

Vaccines can cause adverse effects that sometimes may be as harmful as the diseases they are supposed to prevent. In the case of MMR vaccines, meningitis and symptoms associated with mumps such as facial swelling can occur. Although these circumstances are very rare, some countries have recommended the use of other types of vaccines.

This study is based on an analysis of Brazil’s current experience with its mass MMR vaccination campaign. Although no conclusive data existed for mass vaccination campaigns between 1992 and 1996, in 1997 meningitis outbreaks were reported in several states where mass vaccination had taken place. In order to estimate the risk attributable to each of the type of MMR vaccines used, researchers designed a randomised trial with two groups of people: an estimated 625 000 children aged 1 to 11 years in the northeast of the country. Each group was vaccinated with a different strain of MMR (LZ and URABE). Although the following surveillance of adverse effects in the two groups failed to prove conclusive, based on the Brazilian experience the authors concluded:

The information available in the scientific literature is not always enough to support vaccine safety during mass immunisations campaigns.
Because of the large numbers of people involved in mass immunisation campaigns, the rare adverse effects associated with vaccination can lead to outbreaks of epidemic proportions.
Awareness of the existence of adverse effects depends mainly on the quality of the surveillance system implemented. In the case of Brazil’s experience, these systems varied widely across the country.
The Brazilian immunisation programme has successfully carried out mass campaigns with high levels of coverage. Although the success of these campaigns depended on public trust, this was not eroded by the open debate of adverse effects.

In sum, it appears that the benefits of medical interventions described in the official literature do not always appear within different populations. Secondly, adverse effects associated with the introduction of new vaccines may go undetected unless the appropriate capability exists to assess vaccine safety.

Vaccine safety monitoring should be introduced as standard in any mass-immunisation programme, whilst the roles and responsibilities of policy-makers, the pharmaceutical industry and health organisations must be clarified, so that any dangerous gaps are avoided.

Source(s):
'MMR mass vaccination campaigns, vaccine-related adverse events, and the limits of the decision making process, in Brazil', Health Policy 67(3): 323-328, by S.C. Cunha and I. Dourado, 2004
HINARI subscribers can access the full-text article here. Full document.

Funded by: Fundação Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior (CAPES), Brazil

id21 Research Highlight: 9 November 2004

Further Information:
Sérgio C. Cunha
Instituto de Saúde Coletiva
Rua Padre Feijó, 29, 4 andar
Canela, Salvador, Bahia, Brazil
CEP – 40110-170

Tel: +55 71 245 0544
Contact the contributor: cunhass@ufba.br

Instituto de Saúde Coletiva, Brazil

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