Update since published: NZ introduced varicella vaccine for children on 1st July 2017.
I have just listened to an excellent series of interviews on Radio NZ about the chickenpox (varicella) vaccine. NZ does not fund this vaccine for all children although over the years the various incarnations of the technical advisory group to the Ministry of Health, and now PHARMAC, have been recommending it be introduced. Why would this be I wonder? Perhaps it is a good idea! Below are the reasons for using this vaccine:
Chickenpox can be a miserable disease, sometimes it can be very serious and occasionally it can be fatal. Each year in NZ there are around 55,000 cases and 450 hospitalisations due to chickenpox. Between 2001 and 2011 there were 26 children admitted to Starship Children’s Hospital Intensive Care for the pox, or secondary complications. Eight of these children left hospital disabled after being previously healthy, four died.
- It saves the country money (Here is a cost effectiveness study for NZ)
- People who have chickenpox may develop shingles later in life due to a reactivation of the virus which becomes dormant after infection – this is a potentially debilitating illness as anyone who has had it will attest. Vaccinated children are around 4-12 times less likely to develop shingles.
- The vaccine has an excellent safety profile (Summarised here for NZ decision makers)
- Preventing chickenpox will reduce the amount of antibiotic prescriptions for associated secondary infections, usually Staph. As we all know, antibiotic resistance is a problem facing us all and in this case prevention is way cheaper and less unpleasant than cure.
Question: What about the reasons for not using this vaccine?
Answer: I can’t find any
For some years there has been a school of thinking that constant exposure to chickenpox allowed regular boosting of one’s immunity which helped prevent viral reactivation and shingles (herpes zoster, St Anthony’s Fire or HZ). The other school of thinking is that is not the case. So what does the evidence say? When we reviewed it in 2012 we concluded the following:
Several countries have published mathematical models of the potential impact of the childhood vaccination programme on the incidence of HZ. These models generally predict an increase in HZ over the next few decades, following the institution of a childhood programme, followed by a rapid decline. Vaccinated persons have a lower risk of developing HZ than unvaccinated persons. HZ vaccination has been demonstrated to be effective against HZ and PHN. However, it is still not known whether the introduction of childhood mass VZV vaccination does significantly alter the epidemiology of HZ. Studies that have investigated this issue have been unable to attribute any increase in incidence of HZ to the childhood VZV vaccine programme.
The bottom line is that there is really little evidence that removing chickenpox from the population results in an increase in shingles. However it may play at least a modest role – or it may not. The incidence of shingles has been increasing in many countries regardless of whether or not they vaccinate. In fact rates had often been increasing before vaccination was introduced. If there was a significant causal link between varicella vaccination and increases in shingles you would think some good studies would have determined this by now. More recently, adding to this is a large US study published last year which concluded Age-specific HZ incidence increased in the U.S. population older than 65 years even before implementation of the childhood varicella vaccination program. Introduction and widespread use of the vaccine did not seem to affect this increase. This information is reassuring for countries considering universal varicella vaccination
And while I could list a whole lot of research that shows we probably do not need chickenpox disease to prevent shingles I really just MUST discuss this one paper because it is just soooo cool. The reason it is so cool is that it involves chickenpox, in astronauts, in space.
This study looked at reactivation of the virus in eight astronauts – the picture of good genes, health, and presumably, career happiness.
All eight had previously had chicken pox, evidenced by the fact they had antibodies to the virus. Before launch one of the eight had detectable virus. However, during and just after the mission all eight manifested detectable virus. The conclusion was that the virus can reactivate without causing disease in healthy people who are under stress.
The point I wish to make is that shingles occurs when dormant varicella virus reactivates in previously infected individuals. The virus is kept fom causing disease by exisiting immunity and when this fails shingles ensues. Stress is associated with viral reactivation but as you can see from the astronauts, they did not develop illness and I think we can probably assume they were not exposed to chickenpox during the mission. Another recent study in monks and nuns also supports this, despite not being regularly exposed to chickenpox they are not more likely to have shingles. These and many other studies support the endogenous boosting school of thought, the mechanism that fits best with the observed epidemiology at the moment – in my opinion, happy to revise on further evidence.
So, despite the evidence we still do not have universal varicella vaccination. Why not?
On the 6th March 2013 The Immunisation Sub-committee (the experts on immunisation advising PHARMAC) to PHARMACs Pharmacology and Therapeutics Advisory Committee (PTAC) noted the following:
The Subcommittee noted the impact of the varicella vaccination programme on unvaccinated people getting varicella at a later age if only partial coverage achieved, and on people already exposed to wild varicella at an increased risk of experiencing herpes zoster. However members considered that the evidence for such an effect on herpes zoster is suppositional and that expert consensus was conflicting at this time.
….The Subcommittee recommended the application to fund varicella vaccination for infants as part of the universal childhood vaccination programme with a high priority.
On 23 April they Recommended that varicella vaccine be funded with a high priority for household contacts of patients who were immunocompromised or undergoing a treatment that would result in immune compromise.
In August 2013 PTAC noted in their August 1-2 meeting:
Committee recommended that the application for universal varicella vaccination be declined.
The Committee considered that the risks from a universal varicella vaccination programme, i.e. later age of varicella infection in susceptible individuals and a potential increase in herpes zoster in the elderly, would outweigh the benefit of reduction in varicella infection for otherwise healthy individuals. Members considered that the evidence for the effect of varicella vaccination on herpes zoster and age of infection would develop over time. Members noted that a herpes zoster vaccine was registered in New Zealand and an application for this product should be considered as part of the varicella discussion.
Hopefully we will have universal varicella vaccination in the near future.
I will end by citing one more reason for universal vaccination against chickenpox. Angelina missed her Unbroken premier because she apparently has chickenpox.