Dr Astrid Arellano, Infectious Diseases Physician

A few years ago my children complained bitterly about receiving MenB vaccine – swollen arms that hurt, twice. I’m not sure if it was the evidence or a desire to spite anti-vaxers that lead to vaccinating them again last Christmas, this time with quadrivalent ACWY meningococcal vaccine.

In hindsight, MenB vaccine probably wasn’t necessary as the rate of invasive meningococcal disease (IMD) due to this serogroup has steadily dropped in WA from the predominant serogroup to just a handful of cases in 2015. In contrast, MenW IMD continues to rise nationally from 2% of cases in 1991-2002 to 8% in 2013 and 19% in 2015. In Victoria MenW was the most common notification of IMD in 2015, accounting for 50% of cases.

Nationwide, the predominant serogroups causing IMD vary. MenW has become the most common in Victoria whilst MenB is still the predominant serogroup in South Australia. The reasons for the epidemiological differences are unclear but probably relate to a natural shift in serogroups.

The uptake of MenB vaccine has been too small to account for the steady drop in this serogroup however the decrease in MenC prevalence probably correlates with the introduction of vaccination in 2003 (incidence <0.3/100,000 cases since 2009).

MenW has a higher fatality ratio of around 10-15% and in 20% of cases the presentation is atypical including septic arthritis, pneumonia and epiglotittis. The bimodal distribution of affected age groups (0-5 years and 15-25 years) is similar to other meningococcal serogroups but an additional peak in the older 45 year age group has been noted.

Western Australians aged 15-19 will receive the conjugate meningococcal ACWY vaccine NimenrixTM starting in April/May 2017 via schools and community centres. This program is state-funded and comes at a cost of $6M over the next three years. Sixty to 70% coverage is expected in 2017 with the reduction in meningococcal throat carriage in this age group spilling over other age groups reducing the incidence of IMD.

However, a third of MenW cases in WA between 2013-2016 were in children under 4 years old and 43% were in those over 20 years. The vaccine will not be available in General Practice except on private scripts and children aged 0-5 years are not eligible for free vaccination. Individuals aged 18 and 19 no longer attending school will only have access to vaccination through community centres which may lead to a lower uptake and thus lesser coverage of vaccination.

This program will run for three years and it is hoped that either MenW rates will drop and vaccination will no longer be required or that a national program will replace it. Time will tell.

Key Clinical Points

  • Menincoccal W strain invasive infection is increasing.
  • MenW infection is more dangerous and 1 in 5 cases present atypically.
  • It is intended that the WA government vaccination of teens will reverse these trends.

 

The author acknowledges the support of Dr Gary Dowse from Communicable Disease Control Directorate in preparing the article.

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