The novel coronavirus continues its rampage across the globe. It remains highly infectious and can still cause severe illness and death in a vulnerable population. A couple of months ago, I said that a vaccine remains our best hope to combat this pandemic. So, are we any closer to developing a vaccine for Covid-19?
In order to facilitate the rapid development of a vaccine, the U.S. government initiated “Operation Warp Speed,” pledging $10 billion in partnership with pharmaceutical companies. The goal was to approve and provide 300 million doses of a safe and effective vaccine by January 2021.
First, let’s refresh our knowledge of how vaccines work. Vaccines act by using a weakened or killed version of the pathogen to simulate the infection in the host and initiate an immune response so that the body remembers how to fight when actually infected by that pathogen. Vaccination as a public health tool dates back to 1796 when Edward Jenner developed a vaccine for smallpox. Since then, vaccines have become an indispensable public health tool by helping eradicate many deadly infectious diseases.
The premise behind developing a vaccine for Covid-19 is similar — use a weakened version of the coronavirus to mount an immune response. However, some vaccines in development are using a protein portion or a small fragment of the virus, while others are using the genetic code, RNA, of the virus. Finally, some vaccine candidates are using a different virus as a vector to transfer protein into the host cell. But regardless of the technology used, the goal with a vaccine for Covid-19 is to mount an efficient immune response and to do so safely.
Development of any vaccine is a laborious process, and it can usually take up to 10 years to develop a safe and effective vaccine for an infectious disease. However, with the ongoing pandemic, we do not have 10 years to wait. This has led to easement of regulations, fast tracking of clinical trials and use of emergency use authorizations to hasten the development process. The vaccine candidates still have to go through a clinical trial process, which is usually in three phases. Phase one is done on a small number of people to find the right dose. Phase two is done in a larger group of human volunteers to assess production of an immune response. Phase three is the final phase of the clinical study where it is ensured that the vaccine is safe and effective for the general population.
While there are more than 150 vaccines in development across the world, perhaps the vaccine candidate closest to fruition is the one by Moderna. This vaccine uses messenger RNA, or mRNA, to make a particular protein inside the host cells. The host’s immune system is then stimulated in response to this protein. So when the actual coronavirus infects the host, the body is ready to fight it. This technology is unique and has never been used for any approved human vaccine. This vaccine is currently in phase three trials and is nearing its recruitment goal of 30,000 healthy human volunteers (U.S. participants), and will then deliver 500 million doses per year beginning in early 2021.
Pfizer is also developing a mRNA vaccine based on similar technology as above, and plans to have the vaccine approved for use by December. It will then be ready for mass distribution.
The University of Oxford, in collaboration with AstraZeneca, is developing a vaccine which uses a different virus (adenovirus) as a vector to deliver the coronavirus spike protein into host cells. Preliminary results from this vaccine so far show a strong immune response including production of antibodies and a T-cell response.
Then there are two vaccines in development by Chinese biopharmaceutical companies that are using an unactivated version of the coronavirus in the vaccine. This version of the virus is killed, so it can no longer produce infection but hopefully will induce an immune response.
Finally, a Russian company is also developing a viral vector vaccine using adenovirus. Despite the fact that it is still in phase one trials, Russia recently cleared this vaccine for widespread use but it lacks safety and efficacy data.
It is only a matter of time before we have a vaccine for Covid-19. But the question remains — how effective will it be, and will it be safe? I am confident in our scientists’ ability to provide a safe vaccine — we can lean on decades of vaccinology experience for that. However, it remains to be seen how effective and durable the immunity will be because, so far, the novel coronavirus has proven to be highly virulent and adaptable, and may just have another trick up its sleeve.