COVID-19: Two Modern Vaccine Approaches Still Face Same Old Challenge
Thu, April 22, 2021

COVID-19: Two Modern Vaccine Approaches Still Face Same Old Challenge


In the race for an approved COVID-19 vaccine, numerous companies have applied newer technologies to formulate the most optimal product. These technologies lowered the price and hastened the development time. But like traditional methods, these experimental vaccines face a common struggle.

The common struggle of all vaccine designs is Phase 3 clinical trials. Without the data from such trials, the majority of regulatory bodies will not approve any effective vaccine for public use. At best, an effective vaccine may only be utilized for emergency situations. On top of that, there is a need for mass production. In this pandemic, the reliability and scalability of any vaccine are critical to support the manufacturing of billions of doses.

The Older Technologies in Vaccine Research

The research in newer vaccines has been quite neglected for some time. Due to other major global problems, such as hunger, poverty, and corruption, many governments struggle to allocate sufficient funding to boost vaccine research. Still, several organizations provided support for vaccine researchers to develop better ways to create innovative drugs. With new discoveries in genetic engineering, fresh approaches were born.

“If the new platforms work in a way, that may actually change how other vaccines are produced. So, we may be at the cusp of very much a new technology that we’re going to see for the first time in over a century, basically,” said Dr. Rahul Gupta, senior vice president and chief medical and health officer at the March of Dimes, quoted American news site Vox.

Vaccines have been around for decades and saved millions of lives from numerous diseases, particularly measles, polio, and smallpox. If smallpox was not eradicated, the modern world may be dealing with a smallpox pandemic today. And compared to the current pandemic, smallpox may have taken more lives than COVID-19.

Established vaccines like the MMR and Tdap, were created using older approaches. The most effective approach in providing immunity against vaccine-preventable diseases has been live attenuation. This approach involves a live but weakened form of a pathogen to induce an immune response. However, there is a very small chance the pathogen may turn wild and infect the person. It is one explanation for vaccine-induced polio cases. Both the MMR and smallpox vaccines were developed this way.

Toxoid vaccines use a different approach, wherein the toxic products of a pathogen are the targets. The Tdap vaccine for tetanus, diphtheria, and pertussis target the toxins that cause illness. While safe and effective, toxoid vaccines often require multiple doses to provide full protection. Opposite to live attenuation vaccines are the inactivated pathogen vaccines, which include pathogens killed by chemical or heat.

Pathogens inside inactivated vaccines cannot infect because they are not alive and unable to replicate. But an immune response may cause symptoms like fever. Vaccines for rabies and hepatitis A are derived from this approach. And finally, subunit vaccines that contain antigens of pathogens to induce immunity. Although these vaccines are safe, they usually produce weaker immune responses than the other three.



Modern Vaccine Technologies Emerged Amidst COVID-19 Pandemic

According to Our World in Data, an online source of research data, one reason why vaccination is done is due to herd immunity. It is a scenario wherein nearly everyone in a community has been immunized, which protects those who cannot be vaccinated. As of 2018, 86% of one-year-olds worldwide received the first dose of the measles vaccine, 86% received Tdap, 85% received the polio vaccine, and 69% received the second dose of the measles vaccine.

In studies of herd immunity, the threshold for measles is 92% to 95% of people in a community are vaccinated. For pertussis, the threshold is between 92% and 94% while 83% to 86% for both diphtheria and rubella. For polio, the threshold should be from 80% to 86% while 75% to 86% for mumps. Seasonal influenza has a threshold of 33% to 44% since the strain every year changes.

The hottest of modern vaccine technologies is the mRNA model. It is a little similar to subunit vaccines, in which a part of the pathogen is used. The modern version uses a small portion of the pathogen’s genetic code or the messenger ribonucleic acid. Once introduced into the body, the immune system can analyze the genetic code in a less stressful situation. And when the real pathogen attacks, correct antibodies are already circulating in the body.

The reason why the mRNA approach is preferred than the subunit method is the characteristic of mRNA. It is less stable, shorter in length, and disposable than DNA. Biomedical scientists no longer have to purify subunits or fragments of pathogens. Instead, they can use the pathogen’s mRNA and modify it for vaccine research. The only major issue is mRNA needs to be encapsulated or it will be broken down inside the body before doing its job. Moderna’s COVID-19 vaccine is an mRNA variant.



The next one is the adenovirus vector vaccine approach. This involves an adenovirus strain to carry a genetic material of another pathogen. For COVID-19, the adenovirus bears the spike protein of SARS-CoV-2 to cause an immune response. The big advantage of this is the exploitation of adenovirus in getting inside cells. The big concern is the vaccine’s potential risk in people with compromised immune systems. Gamaleya Institute’s Sputnik V vaccine is based on this approach.

Despite the upsides in these approaches, they face the same problem encountered by older approaches: Phase 3 clinical trials. Phase 3 is the most critical of all human clinical trials. Data from these trials will reveal if a medication or vaccine is safe and effective for a large group of people. If the side effects are acceptable, the product is considered generally safe. If the product performs well, the person will get immunity for life or for several years.

But COVID-19 vaccines at this time are not expected to provide 100% protection against SARS-CoV-2. The vaccines are triggering the body to produce enough antibodies, in case a person contracted the wild virus. It means regular vaccination or additional doses may be required to guarantee some degree of protection. Nevertheless, these vaccines are better than nothing to protect people from COVID-19.