The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the most severe pandemic we have faced in over 100 years. Fortunately, unlike those facing the 1918 Influenza pandemic we have the technology to develop vaccines to help us bring this pandemic under control. After the provision of clean water, vaccines are the most important and effective health strategy. For example, childhood vaccines save an estimated 2–3 million lives worldwide every year and have contributed substantially to the fall in the global infant mortality rate from 65 per 1,000 live births in 1990 to 29 per 1,000 in 2018. The benefits from vaccination can extend beyond the vaccinated individual and benefit the wider community through herd immunity.
Over the past 12 months, the scientific community has made an unprecedented effort to develop vaccines that will provide protection against this newly recognised virus. Vaccine development has been supported by political leaders and huge financial input working with scientists and pharmaceutical companies. Thanks to these efforts we now have 200 vaccines in development including at least 11 already in Phase III trials.
Vaccine development is usually stepwise and typically takes at least 10 years. There are initial studies conducted in laboratories. If these are favourable Phase 1 studies are performed involving a small number of people. This phase assesses safety, dosage and immune results. Usually just a few candidate vaccines move on to Phase II studies during which the optimal dose and schedule, as well as safety is determined. These involve studies that enrol 100 to 1,000 people. Finally, Phase III studies assessing efficacy and safety are completed. These usually involve many thousands of people. Because of the scale of this pandemic instead of the slow stepwise process of vaccine development and then manufacture scientists have combined phases, for example Phase 1 and II, with these phases happening in parallel. Corners have not been cut. Instead, the timing has simply been compressed.
As well as being accelerated in development, the vaccine search against COVID-19 has included some new technologies. While some candidate vaccines use classic methods such as inactivated virus others are using modern platforms including recombinant protein (e.g. whole spike protein) and inactivated viral vectors (various human or chimpanzee viruses which cannot multiply in the cells of the vaccinated person but express the spike protein). In addition, there are some vaccines that have been developed using new methods such as mRNA-based vaccines which have not previously been used for a licensed vaccine. This technology seems to produce a particularly effective vaccine and also one that can be manufactured in large amounts rapidly.
The COVID-19 vaccines all aim to make the vaccine recipient develop protection against the spike protein on the surface of the SARS-CoV-2 virus. This spike protein is vital for the virus to enter a person’s cells and thus invade the body. If the protection induced by vaccination prevents this step, illness won’t follow. The different types of vaccines will differ in how effective they are, in the side effects they cause and duration of protection etc. Different vaccines may work better in different age groups or populations.
Initial study data has focussed on whether a candidate vaccine protects the person who has received the vaccine from COVID-19 illness rather than prevention of infection with the SARS-CoV-2 virus. Therefore, we do not yet know how well these vaccines will be able to prevent someone who receives the vaccine, who is then exposed to the SARS-CoV-2 virus, from being able to spread the virus to another person. This information will come in the next few months.
It is exciting that New Zealand currently has orders for 4 different COVID-19 vaccines. In my next blog I will provide information about how these vaccines work and what we know about them so far.