Vaccines: Some Successful, Others still Awaiting Results
Technology has improved over time. At the end of the second decade of the 21st century, we witnessed the fastest development of vaccines in human history.
By
Atika Walujani Moedjiono
·7 minutes read
Kompas
A nurse prepares an injection of the Chinese made Covid-19 vaccine Sinovac at the Sabiha Uzun Maternal Child Health Center in Ankara on January 15, 2021.
Vaccination as a means to prevent disease transmission has been known for more than a century. Technology has improved over time. At the end of the second decade of the 21st century, we witnessed the fastest development of vaccines in human history.
Vaccines have been used as a means of disease prevention for more than a century. The earliest, most basic form of vaccination took place hundreds of years ago, when Buddhist monks drank snake venom to develop immunity against snake bites. Moreover, variolation, deliberately inoculating healthy people with the cowpox virus in order to protect them against smallpox, was a very common practice in 17th-century China.
This is the practice Edward Jenner adopted and developed in England in 1796, when he injected the cowpox virus in 13-year-old James Phipps. As a result, the boy developed an immune response to smallpox, one of the most infectious and fatal diseases of the time.
Immunization against smallpox has continued since the 18th century, after which the World Health Organization (WHO) expanded its coverage. The effort brought victory to mankind in 1979, when smallpox was eradicated from the face of the earth.
The Covid-19 vaccines are the fastest developed vaccines in history. Starting from China sharing the gene sequencing of SARS-CoV-2 in early January 2020, scientific research into the virus commenced around the world to study how it attacked human cells. This enabled various research institutions and pharmaceutical companies to develop vaccines against Covid-19, with a number of vaccines entering phase three clinical trials and receiving approval for emergency use in less than a year. This is much faster than most vaccines, which require 10-15 years to develop.
Late last year, emergency use authorization (EUA) was granted to several vaccines even as their phase three clinical trials were still underway. Britain, followed by the United States and other countries, including Indonesia, started vaccinating their citizens.
The vaccines that have been granted the EUA include the Pfizer-BioNTech, Moderna, Astra-Zeneca, Sinovac, and Sinopharm vaccines. The Pfizer-BioNTech and Moderna vaccines are both based on the mRNA strand from the SARS-CoV-2 virus. Meanwhile, the Sinovac, Sinopharm, and AstraZeneca vaccines are developed from the inactivated virus.
Technological development
French biologist Louis Pasteur pioneered the development of vaccines that used weakened forms of a virus with the discovery of the chicken cholera vaccine (1897) as well as a vaccine against the deadly anthrax virus (1904).
According to the website of the University of Auckland’s Immunization Advisory Center in New Zealand, other breakthrough vaccines were developed in the late 19th century. From 1890 to 1950, a number of vaccines were developed, such as the tuberculosis vaccine (BCG) by Albert Calmette and Camille Guérin, as well as vaccines for tetanus, diphtheria, and pertussis (whooping cough). The latter three vaccines are today given as the DPT combination vaccine to babies.
From 1950 to 1985, the technology to culture viruses was developed, which resulted in the development of Jonas Salk’s polio vaccine that used the dead virus and Albert Sabin’s oral poliovirus vaccine, which used the weakened, or attenuated, virus. Mass vaccination has almost eradicated the disease, which causes acute flaccid paralysis, from the world.
It was also during this period that the vaccines for measles, mumps, and rubella were developed. Today, measles is a disease targeted for elimination.
Over the last two decades, vaccine technology has advanced with the use of molecular genetics. This has led to the development of the recombinant hepatitis B vaccine and also to improvements in the vaccines for pertussis, tuberculosis, cytomegalovirus (CMV) and the herpes simplex virus (HSV), and has generated new production techniques for the influenza vaccine. Molecular genetics has also been used to develop HIV vaccines and therapeutic vaccines for allergies, autoimmune diseases, and substance addiction.
American researchers Jonathan A. McCullers and Jeffrey D. Dunn wrote in the January 2008 edition of Pharmacy and Therapeutics that gene manipulation allowed the cloning of viral genomes as bacterial or fungal vectors in the laboratory, so that pathogenic organisms would be harmless when exposed to humans. In addition, gene manipulation allowed for the rapid adaptation of microorganisms for use in vaccine design.
One goal is to produce safe and high-quality influenza vaccines according to the circulating virus strains.
AFP/CLAUDIO REYES
A health worker receives the second dose of a Pfizer-BioNTech Covid-19 vaccine at Hospital Posta Central in Santiago, on January 15, 2021.
No results yet
HIV, a virus that attacks the human immune system, was identified in 1984. Despite all the efforts and funds put into developing a vaccine, no successful results have been produced.
Various approaches have been taken in the efforts to develop an HIV vaccine, including peptide vaccines (using small parts of HIV protein), recombinant vaccines, live vector vaccines (using other viruses to transport HIV genes), and DNA-based vaccines.
At least 40 HIV candidate vaccines are in clinical trials. The ongoing trials of candidate vaccines under the International AIDS Vaccine Initiative (IAVI), in the US, Rwanda, Uganda, South Africa and Thailand, are expected to finish in 2022.
The European and Developing Countries Clinical Trials Partnership is also running clinical trials on other HIV candidate vaccines in Africa, Europe and the US. Clinical trials are also scheduled to take place in a number of African countries in the next three years.
Developing a vaccine against HIV is no easy matter because it is very different from other viruses in general. An article published on 16 June 2020 in Healthline said that among the obstacles was the fact that the human immune system was unable to recognize HIV. So far, vaccines have been developed to mimic the immune response of people who have recovered from a disease. The problem is, no one has ever fully recovered from HIV.
Most vaccines are for viruses that enter the human body through the respiratory or digestive systems. Scientists have no experience in making vaccines against viruses that enter through the blood stream, such as HIV. Moreover, HIV mutates very quickly.
KOMPAS/ADITYA DIVERANTA
Covid-19 vaccine injection for health workers at the Puskesmas Palmerah II Village, West Jakarta, DKI Jakarta, Friday (15/1/2021).
Another vaccine that has long been awaited is the vaccine to prevent dengue fever. The disease transmitted by the Aedes aegypti mosquito is caused by four serotypes of the dengue virus (DENV), DENV-1 to DENV-4. No specific drugs or vaccines are as yet available for treating dengue.
According to the WHO, the first dengue vaccine to be developed, Dengvaxia (CYD-TDV) produced by Sanofi Pasteur, is a recombinant vaccine containing genes from the four dengue serotypes. The vaccine was registered in December 2015 in Mexico for use in patients aged 9-45 years. On 1 May 2019, the US Food and Drug Administration (FDA) approved the vaccine’s use for patients aged 9-16 years in endemic areas (Samoa, the US Virgin Islands and Puerto Rico).
The problem was, Suresh Mahalingam and his colleagues at Australia’s Griffith University said in the August 2013 issued of Emerging Infectious Diseases, that when the vaccine was trialed on schoolchildren in Thailand, it showed high efficacy but only for the DENV-1 (61.2 percent), DENV- 3 (81.3 percent), and DENV-4 (89.9 percent) serotypes. The vaccine did not provide protection against DENV-2, the most pathogenic dengue serotype.
The US Centers for Disease Control and Prevention (CDC) stated in 2017 that Sanofi Pasteur revealed that vaccine recipients who had not been infected with dengue were at risk of developing severe symptoms if they contracted the virus after vaccination.
Apart from Dengvaxia, about five candidate vaccines for dengue have been developed. Two of these candidate vaccines are still in clinical trials.
Although many infectious diseases have been controlled successfully with vaccines, a number of diseases are still yet to be overcome. Science still has a long way to go.
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