Getting to grips with an epidemic.

NEW ZEALAND is now in the 14th year of a meningococcal epidemic. Until now there has been no vaccine available for New Zealand's unique and epidemic strain of group B meningococcal disease. Since 1995, 80 to 90 percent of meningococcal disease in New Zealand has been caused by the group B bacteria. The size and impact of the epidemic makes it New Zealand's most serious communicable disease problem. Until now, efforts have focused on early recognition and treatment of the disease, and improving the underlying social conditions affecting its spread, eg housing. Now, New Zealand finally has a powerful biomedical weapon, Meningococcal B Vaccine (MeNZB[TM]), poised to reduce the dramatic effects of the epidemic.

The Neisseria Meningitidis bacteria causes a wide range of diseases, but most commonly meningitis or septicemia. It has been described as an aggressive or raging infection with bleeding into the skin and organs (fulminant infectious purpura). Shock, coma and death can occur in a few hours, despite appropriate treatment. (1) The sudden onset of symptoms and swift deterioration make meningococcal disease a frightening prospect for everyone.

In dealing with this epidemic, New Zealand needs to face some difficult issues. The major burden of disease has been carried by children, with more than 80 percent of cases occurring in those aged 0-19 years. (1) Ethnicity figures show that, before their fifth birthday, Pacific children have a 1:66 chance of getting meningococcal disease; Maori children have a 1:117 chance; and European and other children have a 1:438 chance. Why do children aged 0 to four years living in our most deprived areas account for nearly 50 percent of all cases in this age group? (1)

Parallel to deprivation, other social determinants of health have been found to be major risk factors. The single strongest association is with household overcrowding. While overcrowding is unlikely to have caused the epidemic, it has almost certainly intensified its effect among the most vulnerable. (2) Crowding increases contact among young children and adolescents or adults who carry the organism, and may also increase exposure to infectious co-factors, eg a cough or cold, or to tobacco smoke, further increasing the risk of invasive disease. Overcrowding is often associated with poverty and with increased infectious disease transmission, especially those spread by the respiratory route. In New Zealand, 75 percent of occupants living in crowded conditions are Maori and Pacific people, yet together they form only 20 percent of the population. (2)

While long-term improvements in population health are hoped for, there remains an immediate need to prevent meningococcal infections. The development of the vaccine offers the best hope.

Pharmaceutical companies were not rushing to develop and produce a vaccine needed only for the New Zealand-strain disease in a market that is tiny by international standards. It has been up to New Zealanders to drive the vaccine development, with substantial international technical support coming from the World Health Organisation, among others. While no existing vaccine matched our Group B strain, several "cousin" vaccines were identified. A similar vaccine to MeNZB[TM] was made in Norway in response to a similar epidemic problem and over 300,000 doses given, mostly in controlled studies, with an excellent safety and effectiveness profile. In essence, MeNZB[TM] vaccine is created from a strain change on the base Norwegian vaccine.

Critical challenges of rolling out the new vaccine include the manufacture of sufficient quantifies with tight quality control; increasing workforce capacity to deliver the vaccine; and enhancing the cold chain through such measures as improving quality monitoring nationally and replacing domestic fridges with vaccine specific fridges.

Simple logistics mean simultaneous national roll-out of three doses to all children aged 0-19 is not feasible, so priorities had to be established. Someone has to come first and someone else has to wait, remaining vulnerable to disease--a demanding ethical dilemma.

A feature of the response to this epidemic has been the commitment to hold the most vulnerable children at the centre of all efforts. Clinical trials were conducted in south Auckland, precisely because that has the highest incidence of the disease. The roll-out nationally follows the heaviest geographical load of disease and the age restrictions prioritise those age groups most affected. While final decisions have been made by national experts, the decision-making processes have been transparent and made in close consultation with the populations most at-risk.

Science is endeavouring to keep pace with emerging diseases and vaccine research is at the leading edge of preventative measures. Yet, the attitudes of some public and health care professionals (3) suggest there is a still long road to travel before wholehearted health system commitment to immunisation delivery allows vaccines to protect to their maximum potential. While celebrating the roll-out of MeNZB[TM] and the hopes of epidemic control, I am mindful of other vaccine research pushing new boundaries, eg the Human Papilloma Virus vaccine trials in Auckland and Christchurch that may, one day, help prevent cervical cancer. The time has come to get evidence-based immunisation education on the agenda everywhere.

REFERENCES

(1) Ministry of Health (2004) The Meningococcal B Immunisation Programme: A response to an Epidemic. Wellington: Ministry of Health.

2) Baker, M., et al. (2000) Household crowding a major risk factor for epidemic meningococcal disease in Auckland children. Pediatric Infectious Diseases Journal; 19:10, p983-90.

3) Jellyman, T. and Ure, A. (2004) Attitudes to immunisation: a survey of health professionals in the Rotorua District. New Zealand Medical Journal; 117:1189.

--Natalie Desmond, RCpN, PGCert Public Health, is the national immunisation communications adviser, Immunisation Advisory Centre, University of Auckland.