The success of vaccines has, to date, largely been due to their impact on acute infectious diseases like polio and influenza. However, the future will see scientists focusing on the prevention of chronic diseases like tuberculosis, cancer and Alzheimer’s disease.
Experts at the Mayo Clinic and University of Texas Medical Branch (UTMB) in the US have published a fascinating series of papers looking back at the impact of immunisation against yellow fever and smallpox, and examining future challenges for 21st century researchers.
The growing cost of caring for an ageing population, where non-infectious conditions like dementia will be increasingly common in older people, has added a new dimension to the search for new vaccines. However, the complexity of chronic diseases presents major hurdles that must be overcome.
Older populations need new vaccines
Alzheimer’s disease, the most common neurodegenerative disorder in developed countries, has been at the centre of major efforts to develop therapeutic vaccines.
The primary target has been amlyoid beta peptides – sticky proteins that forms “plaques” in the brain leading to neuronal cell death.
Another protein, known as “tau”, is also receiving considerable attention given its role in dementia but producing a vaccine for a disease associated with the build-up of proteins is proving complex, according to the Mayo Clinic and UTMB.
Scientists have cancers in their sights
HPV vaccines have injected new life (pardon the pun) into the hunt for cancer vaccines leading to increased investment and renewed public expectations. Current vaccines protect against two types of virus which cause 70% of cervical cancers.
It’s not the only cancer vaccine currently available. Indeed, the existing Hepatitis B vaccine reduces the risk of liver cancer but a new approach to cancer therapy is on the horizon – vaccines that treat disease rather than prevent it.
The internet is abuzz with stories promising breakthroughs on new cancer vaccines, many of which are “therapeutic vaccines” that strengthen the body’s natural defences against an existing cancer – rather than providing protection in the way traditional vaccines do.
While cancer vaccines have been sought for decades and it’s still early days for many of the new technologies which could lead to future breakthroughs, dozens of potential vaccines are in late stages of clinical trials.
In the past, plenty of vaccines have fallen at the last hurdle but vaccines for prostate cancer, colorectal cancer, brain tumours, and melanoma (amongst others) continue to look promising. Indeed, a prostate cancer vaccine has recently been given the thumbs up by regulators in the US.
Malaria: battling a versatile foe
Malaria has been a target for vaccine researchers for some time and, while there has been progress in recent years, the complex life cycle of the pathogen that causes the disease is complex.
Its ability to evade the immune response has made it tricky to vaccinate against, prompting researchers to seek new approaches to the problem, according to experts.
A genuine breakthrough in this area would be a huge boost for the millions of people at risk of dying from malaria.
HIV: protecting against a disease that has no cure
With no cure for AIDS on the horizon, the need for a vaccine against HIV is clear. However, the classical methods for developing vaccines have so far proven fruitless for scientists working with HIV.
Most of the current vaccines against diseases like smallpox and influenza work by mimicking natural immunity against reinfection seen in individuals who have recovered from the disease. However, making a full recovery from AIDS is unheard of.
Interestingly, it has been suggested that even if there were a vaccine against HIV, the public may not embrace it as quickly as might be hoped. Their research shows that even if a vaccine that provided 100% protection against HIV were available, only 74% of people would take it.
“One might assume that if an HIV vaccine was available, many people would line up to be vaccinated. However, the research strongly indicates this is not the case,” says Newman, Canada Research Chair in Health and Social Justice. “The availability of a vaccine alone is not enough to ensure that people will be inoculated.”
It seems some are still concerned that potential vaccines in this area would carry the risk of HIV infection – the kind of fear that has dogged vaccines since the Jenner’s time. Uptake would also be affected by the fact that many people believe they have zero risk of contracting HIV.
This suggests that research on public perceptions and communication, as well as active public engagement, will be a key element of the future of vaccines.
The age-old scourge of tuberculosis
Tuberculosis (TB) is broadly under control in the developed world, although its prevalence has risen in Europe in recent years.
The BCG vaccine protects more than 80% of children from serious forms of TB but is less effective in adults, and it has been particularly difficult to demonstrate effectiveness in developing country settings.
Finding the right mix of incentives to encourage companies to invest in finding new TB vaccines is important, according to the WHO. Prizes, tax incentives and advance market commitments have been used to make research in this area viable.
Existing vaccines, new beneficiaries
In addition to finding new and more effective ways of tackling emerging public health threats, there is considerable focus on improving access to immunisation for people in developing countries.
Dr Rino Rappuoli, a leading industry expert, told Vaccines Today that the new technologies will help advance the field of chronic disease. He said that in the field of therapeutic vaccines, there will be greater emphasis on diseases affecting people in the developing world.
“The next thing that will happen is that innovative vaccines for those diseases without a market, that are present only in low-income countries, will be developed. Not-for-profit institutes dedicated to them will play a pivotal role,” he said.
NGOs such as Oxfam say the developing world needs new vaccines but more needs to be done to get vaccines to market quickly and at preferential price.
GAVI – a global health partnership committed to immunisation – has committed to speeding up the rollout of new and under-used vaccines to the world’s poorest people.
The challenges facing researchers, industry and policymakers are many, but optimism abounds. Experts believe immunology is on the cusp of a renaissance.
“We now enter a second ‘golden age’ of vaccinology in the enhanced understanding of common diseases, vaccine development against chronic noninfectious diseases, and in better integrating advances in biology, genomics, immunology, molecular biology, and virology,” according to a paper by Dr Gregory Poland of the Mayo Clinic, and Dr Alan Barrett of the University of Texas.
Listen to a BBC radio programme on the future of vaccines