We all want a vaccine to protect us against coronavirus SARS-CoV-2. One might think it is easy and imagine a chemist grabbing a cookbook and following a recipe of simmering one cup virus for 20 minutes or so on a Bunsen burner to inactivate or kill the virus, adding a dash of adjuvant to stimulate the body’s immune response and voila! You have a vaccine. (That was just sarcasm – please do not try that at home.)
It’s not that simple. If it were that simple, we would have vaccines for all viruses.
Yes; many viruses act similarly in that we get them, produce antibodies, recover and have a period of immunity. Yet, other viruses such as human immunodeficiency virus (HIV) are lifelong infections due to the nature of retroviruses that become incorporated into the infected person’s genome. This retrovirus mutates as it reproduces, it can easily escape the immune system’s surveillance and develop resistance to existing antibodies. SARS-CoV-2 is a beta coronavirus of a completely different virus family.
Our point being is that viruses are diverse. They come in different shapes and structures, are either of DNA or RNA type, have different kinds of genomes within the DNA or RNA, are enveloped or not, infect different hosts and have different routes of infection.
Think about it from this perspective:
- HIV – No approved vaccine. Vaccines have been attempted since 1987. Currently, few are in various stages of development or trial, but again many attempts have failed to protect against this elusive virus.
- Herpes simplex virus-2 (HSV-2) – A vaccine against genital herpes does not exist, we know of one heading to human clinical trials.
- Chickenpox – The U.S. Food and Drug Administration (FDA) first approved a vaccine against chickenpox in 1995. Chickenpox is also a herpes virus, but this vaccine will not provide cross-protection for HSV-2.
- Human papillomavirus (HPV) – HPV vaccines were only approved 14 years ago in 2006.
In essence, the number of vaccines against viruses are increasing substantially due to current technology, but usually take 10-15 years to develop. Indeed, clinical trial development is a three-stage process in and of itself.
So, why do vaccines take so long to develop? We need to make sure they are safe, efficacious and effective. Researchers have several considerations regarding safety and efficacy for vaccines against all viruses, such as:
- The genetic code of the virus.
- Is the virus mutating?
- The genetic code of individuals receiving the vaccine.
- What dose (amount) works best?
- Are boosters needed?
- How does the immune system react to it?
- What type of vaccine is it?
Research teams are exploring inactivated killed, weakened (modified-live; attenuated live), DNA, RNA, protein subunit, virus-like particles, and replicating and non-replicating viral vector vaccines against coronavirus SARS-CoV-2.
- The health of individuals.
Three vaccine types exist against human influenza virus strains: inactivated influenza vaccine, recombinant influenza vaccine, and live attenuated (weakened) influenza vaccine. The Centers for Disease Control and Prevention (CDC) does not indicate a preference. However, the CDC provides a checklist of who should not receive the live attenuated influenza vaccine – administered through a nasal spray – that includes age, history of allergic reactions to components in the vaccine, pregnancy and the person’s immune status.
- Adverse vaccine events.
Vaccine reactions can occur in any species. In people, one of the more serious adverse vaccinal events has been associated with the use of heavy metal adjuvants like thimerosal (mercury), aluminum salts added to vaccines to enhance their potency. The ASIA syndrome (Autoimmune Syndrome Induced by Adjuvants) as coined by Shoenfeld and Associates is one example.
In animals, a well-established example is infectious canine hepatitis virus (canine adenovirus-1; CAV-1), which can cause corneal edema, also known as “blue eye”. One of the adverse vaccine events of the original, modified-live vaccine against canine adenovirus-1 was blue eye – a condition that the virus itself can cause. Both the virus and the vaccine can cause a manifestation of this type III hypersensitivity. To avoid blue eye from the vaccine, it was discovered that the injected, modified-live canine adenovirus-2 (CAV-2) provides cross-protection against CAV-1. By the way, CAV-2 causes minor respiratory illness (kennel cough) in dogs.
- Will the vaccine be effective?
Even though sometimes a vaccine for one virus can cross-protect against another virus; other times it cannot. Scientists can look for clues and hallmarks between viruses, but we do not really know until clinical trials begin.
For example, two ambitious Stage III vaccine trials for HSV-2 (herpes simplex) were started in 1993 and enrolled almost 2,400 people who were negative for both HSV-2 and HIV. Some participants received a placebo instead of the actual vaccine. They were then tested again a year after final inoculation. Despite producing an antibody response similar to natural HSV-2 infection, vaccine recipients acquired HSV-2 infection at a rate similar to those receiving the placebo, 4.6% of placebo group versus 4.2% of vaccine group.
- From the business perspective, can manufacturers bring a vaccine quickly, safely, cost-effectively and profitably up to scale for mass distribution?
- Will the vaccine be produced safely?
The Cutter Incident of 1955 was – unfortunately – a real wake-up call for the United States. Cutter Laboratories produced a vaccine against polio. After a series of missteps and ineptitude, the company sent out live polio virus. Subsequently, 250 people actually came down with polio.
As you can see, the last thing we need is to create an additional crisis on top of the current pandemic.
Currently, more than 90 vaccines are in development against coronavirus SARS-CoV-2. Due to the enormous amount of research and innovation occurring, it is reasonable that a few vaccines against SARS-CoV-2 will be approved by Autumn of 2021 and available en masse by the same time in 2022. At this time, we have to stay positive, hope, and trust that the scientists and companies will produce a vaccine that will be safe and efficacious.