Dr Stanley Plotkin, who was pivotal to the discovery of the rubella vaccine in the 1960s and edits the standard text book on vaccines, believes new scientific knowledge has transformed immunisation and will lead to more vaccines for adults and adolescents. He also expects breakthroughs in how vaccines are made, distributed and administered.
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Where do you expect vaccine development to focus in the coming decades?
There are still many acute infections that merit vaccines and I do see development of many of those in the near to middle future, especially HIV, Malaria and TB. Aside from those targets there is the prospect of a vaccine against dengue, nosocomial or community infection like staphylococcus, streptococcus and Clostridium difficile.
Will much of the progress in vaccine research in future focus on chronic diseases?
Certainly there will be attempts to develop new vaccines against chronic infections – like Hepatitis B and Hepatitis C. Cytomegalovirus, a major cause of congenital infection and transplant disease, is another active area.
The prospect of interfering with cancer-producing chronic infections – Epstein-Barr virus, Hepatitis B and HPV [human papillomavirus] – is receiving a lot of attention. There is also a great deal of interest in vaccines against non-infectious diseases and, again, cancers are the obvious targets.
In the US we already have a licensed vaccine against prostate cancer which is supposed to ameliorate the course of the disease. Alzheimer’s disease, hypertension, drug-abuse – all are the subject of multiple efforts for vaccine development.
What about diseases which are common in the developing world?
Well, we’ve recently seen a vaccine against meningococcal type A developed for Africa. That’s not new technology; it’s old technology adapted to use in Africa. Vaccines against parasitic infections are also an ongoing focus of research. The problems there are more technical than otherwise. If a potent vaccine were developed I think a mechanism would be found to manufacture and distribute it.
I would agree that not enough people are working on infections that are primarily third world infections. There has been some progress – think about Japanese encephalitis for which there are now two potent vaccines against the disease. Dengue fever is another example. So the picture is mixed but not entirely negative.
Ebola is a rare infection but very serious and there are a couple of experimental vaccines in the works. The same goes for chikungunya.
What are the barriers to making major advances in these areas?
If the burden of disease becomes sufficiently clear, development will occur but we need new ways to make and distribute them to the people who need them most.
The situation now is that we can produce antigens in a variety of ways but one has to know which antigens to produce. We need to understand the pathogenesis of disease – we don’t always know which are the important antigens when there are several targets. Malaria is an example. There are dozens of candidates being studied.
How has molecular biology changed vaccine development?
It has been revolutionary because it allows us to make anything we want to make.
Are there advances coming down the tracks in the ways vaccines are administered?
No doubt. First of all, combining vaccines is an important step. One doesn’t have to give as many injections these days. Transcutaneous vaccination is now a fact in Europe for influenza. Certainly, methods of introducing vaccines through skin are multiple. Aerosol has been well developed for measles and could be developed for other antigens. Oral vaccines are more problematic due to the difficulty of evading the tolerance mechanisms of the gut but there are interesting technical advances in that area. The sublingual administration of vaccines is another method which could become more important.
If there are fewer injections will this increase acceptability?
I don’t think so. Opposition to vaccines is more conceptual than fear of injections. Coverage would increase slightly if vaccines were not injected because people who are afraid of injections would probably submit to other means of immunisation but that’s not the issue for most people who oppose vaccination. For example, the intranasal influenza vaccine doesn’t have to be injected and yet it has not taken off; it hasn’t dramatically increased the rate of vaccination.
At present, most vaccines are received during childhood. Will adults receive more vaccines in future?
There is certainly already a move in that direction. There are several vaccines for adolescents and a limited number for adults but that will inevitably change. Of course, children will need to be protected against the things we protect them against at the moment.
Dr Stanley Plotkin is emeritus professor of paediatrics at the University of Pennsylvania, an editor with Clinical and Vaccine Immunology, and a consultant to the vaccines industry. He was speaking to Gary Finnegan.
Click here for a video interview with Dr Plotkin published by History of Vaccines