On 20th April, 2020 our Specialist Veterinary Adviser sent the following message to member vets regarding the new vaccinations

Dear Colleagues, 

We here at the RWAF are receiving lots of questions about rabbit vaccination from vets in practice. And whilst we would suggest that the decision as to WHETHER to restart vaccinations is one that practices need to make for themselves, following the current advice from RCVS/BVA/BSAVA, we are being asked about the timings of vaccination regimes, and hope that our additional advice below is useful. 

Firstly, many vets have described their biosecurity strategies to mitigate risk to practice staff and clients, (eg keeping clients in their car, collecting the rabbit in its carrier and bringing into the practice for examination and vaccination, disinfecting the outside of the basket before and after, and avoiding the use of cardboard carriers), and we would strongly recommend continuing with those precautions throughout. 

We are being asked 2 main questions. 

1. Should you give both the Nobivac Myxo-RHD1 AND an RHD2 vaccine together, in order to reduce the number of visits 

2. How long over the due date should one extend the vaccine interval? 

1. Should you give both Myxo-RHD1 AND an RHD2 vaccine together, in order to reduce the number of visits

This is a tricky one. On the one hand, giving both vaccines together is off licence. This is a regulatory fact, and not one I can change! But I would argue that this is due to the fact that each vaccine is made by a different company, and they simply haven’t been evaluated together, thus the standard VMD instructions for Immunologicals comes into play, putting 2 weeks between the 2 products. One is permitted to go off licence, down the Cascade, where appropriate and with full and informed consent. The suggestion has been made that 2 vaccines at once = twice the risk of side effects/SAR, and I think that whilst that may be true (and don’t forget that a vaccine not working counts as a SAR!), the alternative is the risk of 2 separate reactions for that rabbit, which is not necessarily any better, and could be worse if such reactions are severe enough to require in patient treatment.

In addition, given that there is work from MSD to show that Nobivac and Filavac do not serologically interfere with one another, supporting the science of giving the vaccines this way, at least.

Against that, giving both vaccines together is effectively halving the number of visits, which has got to be a good thing for practice and owner right now. I personally feel that some rabbits are so stressed by the visit to the vets that, even without having been given anything, they will be quiet and potentially go off food for a day or so after the visit. As evidence, it was not uncommon for companion rabbits coming to Bristol for referrals, accompanying an ill bunny, to be “off colour” for a day or 2, from driving to and from the practice, and spending a few hours in a prey-only ward, so its worth considering how many of those vaccinated rabbits are off colour from the visit alone, in which case, half as many visits is a good thing…

Ultimately, this is going to require good communication with owners, and you may decide to treat each case on their merits and your knowledge of their past responses, and to give the owners the choice, based on the above.

2. How long over the due date should one extend the vaccine interval?

I know that increasingly, the DOI for dog and cat vaccines has been investigated, queried, and generally extended. And this has been based on some fairly heavyweight evidence including serology, and statement from BSAVA/WSAVA. This evidence simply isnt there for rabbit vaccines, some of which are so new to market that the DOI has been re-evaluated (and increased!) over time as previously it hadn’t been used for 12 months yet. Based on anecdotal information only, and in the absence of scientific evidence, I would not consider the Myxo component of Nobivac Myxo-RHD to last significantly beyond 12 months, and at present, we have licenced DOI’s for Eravac RHD2 of 12 months, and Filavac for 12 months (although the FRENCH AGENCY FOR VETERINARY MEDICINAL PRODUCTS report demonstrates a DOI in laboratory conditions of 18 months for the RHD2 component ONLY). I’m not suggesting extending the interval to that much as a standard, but it gives me some confidence that a few months over would not be too much of an extra risk for that component only .

Another factor worth considering is that the new Nobivac Myxo-RHD plus is due out in the next few weeks. This is our advice for when this vaccine is available, and may sway your decision making:

A. Rabbits not previously vaccinated with Myxo-RHD

·   Vaccinate asap with Myxo-RHD PLUS

B. Rabbits previously vaccinated with both Myxo-RHD & an RHD2 vaccine

·         Vaccinate at next booster time with just Myxo-RHD PLUS                      

C. Rabbits previously vaccinated with Myxo-RHD but not with an RHDV-2 vaccine

·   Vaccinate with Filavac or Eravac as soon as possible

·   Follow up with a dose of Nobivac Myxo-RHD or Nobivac Myxo-RHD PLUS

·   Next year onwards boost with Nobivac Myxo-RHD PLUS at the time when the RHDV-2 vaccination falls due

Kind Regards,

Richard

Richard Saunders BSc (Hons) BVSc FRSB CBiol DZooMed (Mammalian) DipECZM(ZHM) MRCVS 

RCVS Specialist in Zoo and Wildlife Medicine (Mammalian)

European Specialist in Zoological Medicine (ZHM)