A personalized vaccine has the potential to create the next golden age in the field of immunization and vaccinology. The basic idea of such a vaccine is one vaccine for one patient, which differs from the traditional vaccine concept, i.e., one vaccine for all patients. Various successful trials to treat cancer and infectious diseases with personalized vaccines have been conducted.
The ultimate goal of vaccination is to improve public health by reducing the chances of infection and severity of diseases and increasing the longevity of the host immunity. Hence, to meet the vaccination goals, it is necessary to understand the mechanisms of both immune response and adverse effects of vaccine components in the host. Every host is different; that is why the reactions of each individual towards disease and treatment are also different. Therefore, the personalized vaccine is based on the uniqueness of a patient. Thus, it is given only to that individual patient.
Traditional Vaccinations and their Efficacy
The vaccine contains a small amount of weakened or killed microorganisms, its part or product. When administered to the host body, the body will respond against the same microorganism in the future. A prophylactic treatment induces active acquired immunity by producing protective antibodies and other immune mechanisms.
The first vaccine developed was against smallpox disease by Edward Jenner in 1796, and that was one of the most outstanding achievements in medical science. After developing vaccines and successful vaccination campaigns, many diseases like tetanus, pertussis, rabies, and diphtheria are under control. The elimination of life-threatening illnesses such as smallpox and polio was possible.
Vaccines not only prevent individuals from infections but also protect the whole community against epidemics. Thus vaccines have emerged as lifesavers that reduce mortality and morbidity rates from pathogens.
Principles of Personalized Vaccines
Although vaccine development was a breakthrough, the traditional vaccine development process ignores that every individual is different. Assuming that everyone will react in the same manner immunologically, the vaccine prescription is the same in amount and number of doses universally. Even newer and advanced vaccines may not immunize the public 100%. Understanding the details of different components of effective immune responses is necessary to produce an efficient vaccine.
Researchers are using the patient’s DNA to develop a personalized vaccine. The vaccine antigens aim to optimize outcomes by maximizing immunogenicity and minimizing the risk of either vaccine failure or side effects of a vaccine. Such vaccines are more robust than commercial vaccines and are more suitable for the most vulnerable groups (young and elderly). New and advanced technologies, like analytical and modeling strategies, help to give updated knowledge on; both host and pathogens, the role of innate responses to establish adaptive immunity, the use of adjuvants to increase immunity, and the effect of genetic variation on the host and the impact of microbiome in vaccine response in the host. Such technologies can predict and reduce adverse effects of host-pathogen interaction, vaccine reactogenicity, and risk of severe disease or complications in the host.
Challenges of Traditional Vaccines
Vaccines have success stories but may not be up to the current infectious disease because of many challenges. Some of them are:
- The ineffectiveness of traditional vaccines increased over the period.
- Immunization against some clinical pathogens is complex. E.g., HIV, rhinovirus, tuberculosis, malaria, hepatitis C and different parasitic and fungi lack effective vaccines.
- In contrast, some are reemerging in various forms due to genetic variations, like in influenza virus and coronaviruses causing COVID-19.
- In addition, microorganisms causing severe illness and life-threatening diseases are becoming more resistant. For example, conditions like MDR tuberculosis are hard to treat.
- Live attenuated vaccines uses weakened/attenuated pathogens. But these pathogens can replicate and cause disease in people with immune deficiency or whose immune status is suppressed by certain drugs or cancer.
- On the other hand, killed vaccines are safer but comparatively less effective and require multiple doses. Most cases require a booster.
- The storage of traditional vaccines correctly to retain effectiveness is necessary. Polio and measles immunization failed due to inadequate refrigeration before use.
- Unfortunately, anti-vax attitude, i.e., the behavior of escaping vaccination, is also increasing. People are more concerned about vaccine safety nowadays, assuming vaccine-related illness is higher than the actual risk from the disease. These attitudes are serious public health threats because the chances of diseases now considered eradicated resurfacing in the future are high.
- Scientists suggest the need for a universal vaccine for COVID-19 that works against all beta-corona viruses to minimize the risk of pandemics of COVID-19. However, the purpose of a universal vaccine is challenging, because this virus has high genetic variation due to mutations and genetic recombination within multiple strains.
- Similarly, traditional vaccines need extensive clinical trials for safety and efficacy. Also, traditional vaccines focus on infectious diseases, but today non-communicable diseases are spreading worldwide.
Personalized Vaccines; Benefits and Applications
Personalized vaccines, which are more potent than commercial ones, work against many infectious diseases, allergies, and cancer. These vaccines avoid many clinical trials minimizing serious illness and unnecessary costs.
Personalized vaccines help avoid unnecessary doses or types of vaccines. For example, if an individual’s genotype is such that there is no risk of chronic infection due to HPV or HBV, there will be no need to administer costly three doses of vaccines. Similarly, some immune genotypes allow protection after only a single dose. Knowing about the host system and mechanisms, we can avoid the amounts which are not required. Also, we may alter or even avoid certain vaccines if genotype-phenotype predicts significant adverse effects for a given vaccine. Therefore, personalized vaccines can treat infectious diseases more effectively, i.e., maximizing immunogenicity but minimizing adverse effects.
The principles of personalized vaccines have also been applied in various trials against the recent pandemic of COVID-19. In the study done by Hunziker in 2021 in the USA, an age-personalized dosing strategy (elders first) reduced cases faster, reducing the transmission and death rates and shortening the pandemics. The study also shows that older adults need high doses, whereas in younger, lower doses generate sufficient immunity; this saves the number of vaccines and helps in early vaccine availability to a large population. Vaccinating at a young age helps reduce disease transfer to a high degree. Similarly, different studies have used dose-optimized vaccines to receive excellent immunity.
While developing personalized vaccines, more knowledge of innate and adaptive immunity and host biology can be obtained than ever before, which will be helpful in every area of medical science.
Personalized Vaccines and Cancer Treatment
Personalized vaccines can be a miracle in the treatment of cancer. The concept has already been used in the successful treatment of cancer patients. Since each tumor is different; therefore, the medicine/vaccine which works for one cancer patient may not work for the other. The detailed study of such tumor and host system mechanisms is applied to create personalized vaccines in such cases.
Method Used to Develop Treatment for Cancer
- Firstly, compare the DNA from a patient’s tumor to the patient’s own healthy DNA.
- Sequence the DNA of normal cells with that of tumor cells. A unique set of mutations in tumor cells can be distinguished.
- Computers are used to identify mutations in a patient’s cancer by simultaneously sequencing the two DNA samples, capturing specific features of an individual tumor.
- Create a set of genetic instructions that encodes each mutation by using the results. All the instructions are then loaded into a vaccine and injected into the same patient as a personalized vaccine.
- Once the vaccine is injected into the patient, the injected molecule tells body cells to express portions of protein on their surfaces. It teaches the body’s immune cells to recognize the mutations in cancer. Finally, it attacks and destroys the tumor, and only that patient receives this vaccine.
- Together with the vaccine and immunotherapy, the immune system will be able to kill cancer.
Limitation of Personalized Vaccines
- The concept of a personalized vaccine is new, and the proper understanding of such ideas is challenging. It needs a detailed account of host-parasite interaction for every individual, which is a complex method.
- Every individual will require a new product/vaccine to personalize a vaccine. Thus it may be time-consuming and expensive. Personalized vaccine development needs advanced technology, costly tools, and highly experienced human resources compared to other commercial vaccines.
Traditional vaccines have challenges in identifying the safest and most effective treatment strategies. Today, as we have vast resources of technologies, combining artificial intelligence and machine learning models can overcome such challenges. Advancements in immunology, genetics, molecular biology, and bioinformatics have demonstrated the value of a personalized approach to therapeutic drug selection. Computational modeling strategies help characterize and understand human immunology at a systems level. Applying the ideas generated from these studies is impossible at an individual level. At least, we can use them to find common genotypes, racial groups, gender, or age group to limit the side effects to minor and temporary, not severe life-threatening.
Hence, the need for personalized vaccines is at both the individual level (like cancer) and the population level (during epidemics and pandemics of infectious diseases) to eliminate infections from the world. The ideas of personalized vaccines have already been helpful in therapeutic cancer vaccines and will probably be used in other clinical areas in the coming days.
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