Friday, February 03, 2006

Vaccinations and public paranoia

Should a vaccine be widthdrawn because the disease itself is rare and public confidence in it is lowered? Such is the debate Nature discusses this week with regards to making a new vaccine available for treating Lyme disease. Now Lyme disease isn't the most common of diseases, unable to spread between humans it instead is primarily carried from parasitic ticks that are found on deer to people living near these animals. Unfortunately, despite this the disease is on the increase, possibly due to other animals serving as vectors for transporting ticks and higher contact between people and deer.

Lyme disease, first described by Allen Steere in 1975 after an outbreak of arthritis in children living near Lyme, Connecticut. In the short term it was discovered that Lyme disease causes some fairly nasty flu-like symptoms, a rash and sometimes neurological problems including meningitis. Over time, the disease starts to manifest itself as delibilitating joint pain later progressing to a form of arthritis. As it turns out, this disease was caused by a spirochate bacterium called Borrelia burgdorferi that was spread by deer ticks. Later, patients claiming to have suffered an infection with the organism had symptoms similar to chronic fatigue syndrome, although Steere disagreed that there was any association (leading to the "Lyme Scandal").

Although antibiotics are very effective such as oral amoxycillin if caught early, the treatment for more chronic manifestations is far from pleasant. Essentially, this involves the injection of several antibiotics intravenously into the body over several weeks to eliminate the organism. Eventually, one of the major drug companies, GalaxoSmithKline produced a vaccine using a structure on the outer structure of the bacterium called OspA. Unfortunately, speculation that quickly spread among the public that the vaccine may be associated with autoimmune disorders put an end to the vaccine. While these claims were never substantiated by the FDA or the CDC, they still put an end to the vaccine which was widthdrawn from the market.

Now another company, Baxter vaccines based in Austria has decided to have another crack at producing a vaccine against lyme disease. In this particular case, they have used a vaccine again based on the OspA protein, essentially re-releasing the previously failed GalaxoSmithKline vaccine with one key modification: The removal of a small protein sequence. This short protein attached to OspA was the one at the center of a large debate over the possibility of the original vaccine causing an autoimmune disorder. It was hypothesised that because this short protein resembled that of another human protein, it might cause the immune system to make a 'mistake' and attack self proteins. This process, known as 'molecular mimicry' was assumed to be the cause of the later arthritis that manifests after an infection with Borrelia burgdorefi.

Over time however, no study has demonstrated that the molecular mimicry hypothesis surrounding OspA is correct and that a wide range of protein sequences can activate the immune cells involved and with widely different sequences, dealing heavy damage to the molecular mimicry hypothesis. Even so, the new vaccine will lack the particular protein sequence of the original in order to avoid public controversy.

The development of a vaccine surrounding lyme disease tells an interesting story about how misguided public opinion can often be the death of a vaccine. Although not widely spread, the concern over side effects (real or imagined) often paints a more pressing picture in the publics mind rather than the actual infectious organism in question. In many respects, this is merely the symptom of a society that has benefitted from the widespread use of vaccines and antibiotics that have wiped out most common infectious diseases already. The lessons learned from the failed introduction to lyme disease could also be applied to other cases, including the recent introduction of MeNZB to New Zealand.