Epidemiology of Meningococcal Disease in New Zealand in 2006

Epidemiology of Meningococcal Disease in New Zealand in 2006
Date of publication: June 2007

Summary
This report was prepared by Environmental Science and Research Limited (ESR) for the Ministry of Health.

Introduction
Reviews of meningococcal disease epidemiology in New Zealand have variously been published since 1991. This report provides 2006 data and some comparative historic data.

Surveillance Methods
Surveillance of meningococcal disease is based on the combination of disease notification and laboratory data. Isolates and/or meningococcal DNA from cases of disease are fully characterised enabling monitoring and reporting of disease incidence by group and strain type.

Incidence and Distribution
Cases of meningococcal disease notified in 2006 numbered 160, a rate of 4.3 per 100 000. This is the lowest number of cases notified since 1994. Since 1991, the start of the epidemic, the total number of notified cases is 6023. The number of confirmed cases in 2006 was 145, giving a confirmation rate of 90.6% which is the highest confirmation rate since 1994.

The rate of disease of 4.0 per 100 000 population in 2006 is still significantly higher (2.7 times) than the pre-epidemic rate of 1.5 per 100 000 (1989-1990) but is the lowest since 1994. The highest rate of disease of 17.4 per 100 000 was recorded in 2001.

The highest age-specific rates of disease continue to occur in children less than five years of age, although the rates in 2006 were less than that seen in preceding years; 60.0 per 100 000 for those aged less than one year and 12.8 per 100 000 for 1-4 year olds.

Although age-standardised rates have decreased significantly for all ethnic groups, Maori or Pacific Peoples continue to experience higher rates of disease than the European population. However, during the course of the epidemic 44% of cases identified as European, 31% as Maori and 20% Pacific Peoples.

Throughout the epidemic, highest case numbers have consistently occurred in the upper North Island, particularly in the Northland, Counties Manukau, Waitemata, Auckland and Lakes District Health Boards (DHBs). Consistently the Nelson-Marlborough region has experienced the lowest case numbers.

Seven deaths occurred in 2006 giving a case fatality rate of 4.4%. Since 1991 a total of 245 deaths have been recorded, an overall case fatality rate of 4.1%. The policy of giving antibiotics prior to hospital admission implemented in 1995, has been endorsed by a lower case fatality rate occurring for those receiving antibiotics. Since 1991 the case fatality rate for disease caused by group C has been consistently higher than for subjects infected with group B meningococci.

The epidemic has been caused by a meningococcal B strain with the PorA type defined as P1.7b,4 (P1.7-2,4). This strain caused 18 cases of confirmed disease in 1991 rising to a peak of 370 confirmed cases in 2001. In 2006 there were 74 cases due to the epidemic strain.

In 2001, the Ministry of Health contracted Chiron Vaccines to make a strain-specific vaccine for epidemic control. Following successful age-group trials the delivery of MeNZB™ began in Counties Manukau District Health Board (DHB) and some eastern suburbs of Auckland DHB in 2004 and was progressively introduced throughout NZ ending in June 2006.

MeNZB™ vaccine is a strain-specific vaccine targeting the PorA P1.4 on the group B epidemic strain. Rates of disease caused by this strain have decreased while rates for all other meningococcal strains have continued at same levels.

Discussion and Implications
Accurate disease surveillance data including evidence of disease confirmation are vital for the evaluation of the effectiveness of the MeNZB™ vaccine in combating the meningococcal disease epidemic in New Zealand. The established historical dataset provides the information against which changes in disease epidemiology can be evaluated. The number and proportion of meningococcal cases caused by the epidemic strain have decreased significantly since the introduction of the MeNZB™ vaccine in 2004.

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Publishing information

Date of publication: June 2007

Citation: Environmental Science and Research Limited. 2006. The Epidemiology of Meningococcal Disease in New Zealand in 2006. Wellington: Ministry of Health.

Related information

Meningococcal Disease homepage
Meningococcal Disease Publications - including the Epidemiology of Meningococcal Disease in New Zealand reports from 2000