Meningococcal rare but deadly, yes there are vaccines

By Helen Petousis Harris 07/11/2018


Meningococcal disease is scary, really scary. Like many of our most insidious diseases meningococcal disease often presents like a flu, and most people who present with a flu-like illness have… a flu like illness.


How much meningococcal disease is in NZ?

In 2014 NZ had 45 cases and in 2017 there were 112. So far this year there have been 96 cases. The risk is about 2-3 per 100,000 people. In contrast, for flu, this season the rate of visits to the GP for a flu-like illness was over 400 per 100,000, most are under five of age. Note my general extrapolations from this week’s data but you get the point. However health professionals always have to consider the possibility that the person has something other than flu.

Approximate rates per 100,000 population in NZ 2018 based on surveillance data

New Zealand has had its fair share of meningococcal disease. We had a devastating epidemic that raged for about 15 years. A tailor made vaccine was developed (MeNZB) and rolled out to over a million kiwis back in 2004-2008 at the tail end of the epidemic. However, there are several groups of the meningococcal bacteria and these require different vaccines hence complexities.

 

NZs recent Meningococcal epidemics, Group A in Auckland and Group B Nationally

So what is happening now?

Over the last year there has been a jump in the cases caused by serogroup W, a serogroup that does not normally dominate our NZ meningococcal landscape. While all these groups of meningococcal are killers, this particular strain of group W (sequence type ST11) affects all aged and appears super virulent. The numbers of cases caused by this strain have doubled since 2017 from 12 to 24 so far. People who have this strain are more likely to die. To make this worse the signs and symptoms are a bit different from the usual making diagnosis harder. GPs are being prompted to be on the lookout and to administer antibiotics on suspicion.


What sero groups are where today?

Globally there are primarily 5 groups of meningococcal (A, B, C, W, Y) with a couple others here and there (E and X). Most cases in NZ are caused by group B and Group C.

The global serogroup distribution of meningococcal disease. From Miller 2017 https://jramc.bmj.com/content/163/4/235

What about vaccines?

Yes there are vaccines! Here is what we have to hand in NZ and what they can do. For more info go here to the IMAC factsheet but the key table is below (Kudos Karin).

http://www.immune.org.nz/sites/default/files/resources/Written%20Resources/DiseaseMeningococcalImac20180912V01Final.pdf

All but one of the vaccines in the chart are called conjugate vaccines. They are composed of a sugar specific to the serogroup of the meningococcal bug (A, C, W, and Y) which has been chemically joined (conjugated) to a protein that the immune system finds rather delicious. Together the combination induces protective immunity and long lived memory against the sugar in question (A, C, W, and Y).

The vaccine against group B is something else altogether and I have written separately on this as it is such a fascinating topic, but basically the product available in NZ (Bexsero) has been developed with new technology and the formulation includes genetically engineered proteins as well as the active component of the NZ MeNZB vaccine used ten years ago.

Vaccine limitations

The protective effect of all these vaccines is not perfect and not lifelong, expect 5-10 years but don’t quote me. This is because when these vaccines are introduced to a population the disease goes away making it really hard to tell if the vaccine is still protective by comparing the vaccine status of cases – because there are hardly any cases! But based on the rate that the antibodies in the blood wane five years might be about right. If you want to maintain protection a booster dose of vaccine would be in order.

Should NZ fund universal meningococcal vaccine?

We have some disease, it is relatively rare but very, very, nasty. We also have vaccines. If you were a decision maker here just some things to consider.

  • How much diseases do we have? We do not have a raging epidemic like we have had in the past but one could argue that a single preventable case is one too many.
  • Who is getting the disease? We have two key age groups, the very young, and adolescents. Should one vaccinate both age groups?
  • What group/s of disease are you aiming to vaccinate against, because to target all those causing disease in NZ (mainly B, C, and W) you will need two different vaccines.
  • How will you deliver the vaccine/s? When you vaccinate infants will you include a meningococcal vaccine at the same time as the other infant vaccinations or will you administer separately? Will you vaccinate them against just group B or will you also vaccinate them against the other groups? The same questions could be asked about the delivery of adolescent administration.
  • How many doses are required for different ages? Older ages require few doses.
  • If you choose to implement Group B vaccine only how will you explain to the parents of a child that got Group C or W why you did not include a vaccine against that as well?
  • How much will this cost? How much will this save? How much money is available?
  • The Immunisation Technical Advisory Group to Pharmac recommended a group B vaccine for infants and gave it a medium priority. They deferred making a recommendation on group C vaccines.

I considered some of these kinds of questions a while ago when there were decisions made about pneumococcal vaccines. 

Key points

  • Meningococcal disease is rare but deadly
  • A new sequence type of group W (ST11) has emerged and it is particularly virulent
  • We have vaccines that protect against the meningococcal groups circulating in NZ including the new hypervirulent W and the groups B and C that cause most of the cases.
  • The vaccines probably protect for around five years and boosters can be administered
  • There are many considerations around funding a universal meningococcal vaccine programme.