We Need A Better Pertussis Vaccine
The Chinese call it the hundred day cough. In Spanish it is tosferina or “Bark of the Dog.” Pertussis, a.k.a. whooping cough, is a disease that many thought to be a thing of the past, but has been making a comeback for several decades now. Unfortunately, for many infants that comeback has been deadly.
In 2010, California experienced the worst epidemic of pertussis in 60 years with 9,000 cases, over 800 hospitalizations, and 10 deaths in infants under 6 months old. This year, the United States has had the most pertussis cases in 50 years and already 9 infants have died.
Is pertussis really making a comeback? Epidemiologists caution that we just may be better at detecting and testing for pertussis, but the fact remains that of all the diseases for which we routinely vaccinate pertussis is the least well controlled. The U.S. recommended vaccine schedule now calls for 5 vaccine doses (DTaP) by the time a child is 5 with a sixth dose (Tdap) at 11 years old as a booster. Even after six doses the disease is still prevalent, infecting children, and killing infants across the United States.
One main reason for this is that studies are showing that immunity from the current accellular pertussis vaccine wanes in as little as three years. Many people who get pertussis have been vaccinated. In order to control the disease we need a vaccine that will last longer than the normal five year cycle that pertussis tends to follow. This will allow us to reach a herd immunity threshold that will prevent the continuous spread of the disease.
This is not to say we should stop vaccinating with the current vaccine as some in the anti-vaccine movement suggest. Not vaccinating for pertussis with such a high prevalence of disease is extremely risky. 2011 was the first year in 20 years that California did not have a death from pertussis. This means our vaccine efforts have achieved something important. The current vaccine is the best tool we have to prevent the disease. The current vaccine does provide protection but it doesn’t provide long enough protection to achieve herd immunity and put the disease in the box.
For this reason we need a better vaccine. It is time for the government and the private sector to begin research on a more durable pertussis vaccine. No one is suggesting it will be easy, because Bordetella pertussis is a tricky organism. It is one of the most infectious diseases in the world with a high attack rate. The immunity one gets from being infected by pertussis naturally wears off. However, vaccine technology has come a long way and we need to leverage those technological gains and find a way to get this disease under control.
Several experts with whom I have spoken suggest going back to a whole cell vaccine, which is the vaccine we used in the U.S. before, for safety reasons, we switched to an accellular version. The whole cell vaccine conferred longer immunity than the current vaccine but had more side effects. Experts theorize that the side effects from that vaccine can be reduced by removing the reactogenic components (lipopolysacharides or endotoxins) which lead some children to have high fevers and seizures after receiving it. Another possible solution is to change the antigen formulation of the current accellular vaccine to gain longer immunity and more efficacy. Either of these avenues deserves research.
Unfortunately, there seems to be little incentives for pharmaceutical companies to pursue a better pertussis vaccine. The costs of clinical trials under the current FDA structure make pursuing such a vaccine unprofitable. This is an example of market system failure. In this case, the government or another entity like the Gates Foundation needs to step in and work with manufacturers in the name of the public good. This is how the polio vaccine was developed. The time for a better pertussis vaccine is now. This is a major public health issue. Millions of dollars in health care costs are at stake, as are the health and lives of infants.