Tuesday, June 24, 2014

Another reading on an article about the efficacy of rabies vaccination

Eddie and Ripley hang out in their winter jumpers.

If there is one thing I've learned from years of University study, its that no scientific paper is flawless (and if you've submitted a paper you might agree that nothing is as humbling as peer review). When I posted this piece on an article about protection induced by rabies vaccination it garnered a lot of interest.

Associate Professor Richard Squires, from James Cook University, wrote the following comment which makes some excellent points.

It’s actually published in a brand new journal named “Veterinary Record Open” (as in open access), not in the well-established Veterinary Record. 

[I stand corrected]

This article was published in the very first issue of the new journal.  It’s peer reviewed, but the stated aim of the publishers is to achieve very rapid peer review.

There’s no information in the paper about the quality of the rabies vaccines previously administered to these 300 dogs.  Some of the locally produced rabies vaccines in India are of questionable efficacy.

They used a “home-made” antibody titre test, with their results calibrated indirectly against international standards.  So the accuracy of the statement that “only 39.67% of previously vaccinated dogs had a protective titre” hinges upon whether their indirect calibration was reliable. Some direct cross-checking would have been good. They don’t tell us how many of the dogs had a “nearly” protective titre, so I can’t judge how important this issue might be.

We know that (single) vaccination and release programs have been highly effective, in the field, in some parts of India and Sri Lanka (for example, in Colombo, human deaths from dog-bite derived rabies were reduced from about 35 per year to 0 to 2). 

In addition, it is possible (but not safe to assume) that some dogs with suboptimal antibody titres would mount a rapid and effective immune response after the bite of a rabid dog.  The virus persists at the bite site for a while before getting into neurons, where it can evade the immune system.  It can be destroyed at the bite site if antibody levels rise rapidly after a circulating memory B cell encounters virus at the bite site, shortly after the bite.

I have hopes that oral rabies vaccine (a single dose per dog) can and will be used to control canine and human rabies in India, Sri Lanka and other countries where urban rabies is mainly a consequence of dog bites.  There is evidence (not least from wildlife vaccination programs in rich countries) that this approach can work.  I would envisage training people who habitually feed street dogs (via a DVD or web page) to maximise the number of dogs they can immunise (by feeding street dogs empty baits over several consecutive days to overcome mistrust of the bait and then feeding them vaccine-impregnated bait on the last day).

Thank you Dr Squires for this thoughtful response. Meantime I certainly wasn't pooh-poohing rabies control initiatives - far from it. We all need to contribute to the fight against this devastating and deadly pathogen.

If you have an interest in infectious diseases in general read this fantastic interview with Associate Professor Tom Gottlieb here.