Infectious diseases still account for around 40% of all recorded deaths in the world.
Advances in vaccine technology are crucial to limit and prevent infectious diseases around the world, which still account for around 40% of all recorded deaths globally.68 Changing how existing vaccines are used, developing new vaccine delivery technologies and generating new vaccines are some of the ways researchers are working to overcome this ongoing challenge and save lives.69
Many technologies under development will improve the effectiveness of vaccine delivery and make it simpler.70
To make a vaccine that only needs to be given once, it must either be very powerful or packaged so that its contents are released intermittently once it has been administered. Technologies and alternative adjuvants that can remove the need for multiple shots are under development.71–73
Currently, many vaccines need to be injected—an experience that people can find unpleasant, and may be a serious psychological barrier for some. Needle-free administration is already possible for some vaccines, such as live vaccines given orally (e.g. rotavirus). Researchers are working on edible plant-based vaccine materials, needle-free skin patches and microneedle injection technologies to get the vaccine through the skin without discomfort.71,72,74
Technologies for delivering multiple antigens in one injection are improving. Many different inactivated vaccines can already be given in one injection without impairing the immune response to any of them, and some live virus vaccines can also be given in one injection.75,76 That means fewer needles for patients and more efficient vaccine delivery overall.
Most successful vaccines protect against acute (short-lived) infections largely through the production of antibodies. Vaccines for chronic (long-lasting) infections, especially for HIV, tuberculosis and malaria, remain a challenge. One of the primary reasons for this is that the viruses, bacteria and parasites causing these infections hide from the immune system inside the person’s cells. To overcome this, a different kind of immune response involving T cells is required instead of, or in addition to, an antibody response.77
There are some infections associated with serious long-term complications that we don’t yet have a vaccine for. For instance, infection with the bacterium Helicobacter pylori means patients are more likely to develop stomach cancer, and group A streptococcus infection is responsible for rheumatic fever, which is still a significant cause of death and disability in developing countries.78,79
Based on experience with emerging infections like Ebola and Zika, progress has been made in developing vaccines that use mRNA (a type of genetic material) to stimulate some of our own cells to temporarily produce antigens.80 The research and progress made in this field contributed to the speed of development for COVID-19 vaccines.
Vaccines also have the potential to be used to treat diseases, rather than prevent them. Such therapeutic vaccines are being targeted at persistent infections, such as shingles and those due to human papilloma virus. They are also being targeted at non-infectious conditions, including autoimmune disorders, tumours, allergies, and drug addiction.
In the case of tumours, the vaccine can either be directed against the tumour itself or be designed to amplify the anti-tumour immune response. For autoimmune or allergic disorders, vaccines are being designed to switch off unwanted immune responses (so-called ‘negative vaccination’), rather than switching on the useful immune response needed for infections and cancer.81
Promising trials are in progress for vaccines to treat nicotine and cocaine addictions.
COVID-19 infection is caused by the SARS-CoV-2 virus, which belongs to the coronavirus family. This family includes the original SARS-CoV virus responsible for the SARS epidemic of 2003 and several other coronaviruses that cause the common cold.
SARS-Cov-2 is thought to have been transmitted to humans by an animal carrier. The virus carries a ‘spike’ protein that allows it to attach to human body cells, where it then enters the cell and reproduces.
The World Health Organization officially declared COVID-19 a pandemic on 11 March 2020.82 To date, the disease has led to severe illness and death in millions of people around the world. COVID-19 mainly affects the lungs but can also damage other parts of the body, including blood vessels, kidneys, heart and brain.
The increased development speed of vaccines for COVID-19 are a result of improved and new vaccine technologies being available, substantial investment, international collaboration between scientists and increasing the speed of regulatory review.
The scale of the COVID-19 pandemic has demonstrated the essential role of vaccination in today’s world. Several vaccines were produced and implemented in vaccination programs globally within the first year after the onset of the pandemic, compared with the previous average vaccine development time of 10 years.83 This reflects advances in vaccine technology that will assist us with other infectious diseases, not just COVID-19.
The rapid development of vaccines for COVID-19 is also a result of substantial investment, international collaboration between scientists and increasing the speed of regulatory review. These factors, combined with advances in vaccine technology, have enabled effective vaccines to be created and brought to market in record time while completing clinical trial phases and receiving all mandated regulatory and safety approvals.
COVID-19 vaccines are being heralded as one of the leading solutions to control the pandemic and resume our previous way of life. Ensuring public confidence in the COVID-19 vaccines is crucial to facilitate vaccine uptake.
Despite decades of scientific research into vaccine safety and effectiveness, some people may still have concerns about vaccines, or may think that some diseases are not severe enough to need a vaccine.84 The spread of misinformation about vaccines can also make it more difficult for people to understand whether a claim is based on credible scientific evidence.
Good communication about the risks of vaccine-preventable diseases and the safety of vaccines is important for everyone. Discussing concerns with a trusted health professional is one of the best ways for people to understand what scientists and public health professionals know about a disease and the best protection against it.85 However, it is equally important for health professionals to listen openly to those concerns.86
Ensuring that key groups are protected against infectious diseases is crucial. In Australia, between 30 and 50% of pregnant women currently receive maternal influenza vaccines, and while vaccination rates for children under five years are relatively high, there are still many more opportunities to ensure these groups are receiving the highest levels of protection. Making sure people are confident that vaccination is the best way to avoid diseases is important, especially in the case of a global pandemic like COVID-19.
Developing a better understanding of the practical barriers to vaccination, as well as the social, cognitive and emotional aspects of making decisions about vaccines, will help everyone to feel more confident about keeping their immunisations up to date.87 Although the science of vaccine development is critical, it can only be fully effective when people actually receive their vaccines. The act of vaccination saves lives.
© 2021 Australian Academy of Science