Oxford/AstraZeneca Covid-19 vaccine – a simple overview
Dr Lauren Wise
WITH the arrival of South Africa’s first batch of Covid-19 vaccines this week, many questions have surfaced around how they work and whether they are safe.
Social media has been abuzz with misinformation, disinformation and conspiracy theories which are all contributing factors to vaccine hesitancy in the public.
It therefore becomes necessary to resolve these issues as vaccines are in fact a life-saving solution to the global pandemic.
The Oxford/AstraZenenca vaccine, a million doses of which landed at OR Tambo International Airport on Monday, has been developed by doctors and scientists and has been tested thoroughly in humans. It has passed the necessary clinical trials and regulatory reviews that are required for human medications.
Although this process happened in a shorter time than usual for vaccine development, no shortcuts were taken in the process.
This vaccine is relatively easy to produce. It is being produced in India, where 60% of the world’s vaccines are already produced and where they already have the special facilities required to safely manufacture this vaccine.
How do vaccines work?
Viruses are non-living organisms. They cannot multiply on their own and have to get themselves inside a host cell where they hijack the host’s protein-making devices to make more of their own protein building blocks to make new viruses.
The AstraZeneca vaccine is a Vector Vaccine. In this type of vaccine, another virus (one that cannot cause illness in humans) is used as a carrier or “vector”. The vector transports the vaccine components into our cells.
Only the gene of the Spike Protein (a part of the Covid virus’s outer coat that is easy for our immune cells to “see”) of the SARS-CoV-2 virus is put inside the carrier virus. This single gene of the SARS-CoV-2 virus cannot cause illness in us because it is only one tiny part of the outer shell of the Covid virus.
At this point, the Spike Protein gene is well hidden inside the carriers. These are injected into a person and the carrier virus goes into our bodies and attaches to our cells. They then push the Spike Protein gene into our cell. Our cells’ protein-making parts then make hundreds of copies of these spike proteins. These hundreds of spike proteins are released into our body. They are recognised as foreign or “not self” and are destroyed by our immune system.
The immune system remembers the viral protein so it can defend against it far faster if it is in our body again.
Immunity is very complicated but in essence there are 3 steps:
1. Recognize the invading “germ” (in this case the SARS-CoV-2 virus)
2. Make specific antibodies that destroy the invading germ
3. Make memory cells so it can recognise the invader quickly if it comes into the body again.
If it’s the first time your immune system has ever seen a foreign “germ”, steps 1 and 2 take time and use lots of your body’s energy. During this time the germ makes you sick. How sick depends on the type of germ and how strong your immune system is in making new antibodies. Your immune system then goes on to make memory cells as you get better.
The point of a vaccine is to stimulate all three steps of the immune response without the person getting sick. In the case of the CoviShield vaccine, by only giving an outer coat Spike Protein of the SARS-CoV-2 to the patient and not the whole virus, it is impossible to get the Covid illness. However, your immune system learns to recognise the Spike Protein as bad and creates antibodies to kill them.
A vaccine should, most importantly stimulate your immune system to memorise and be able to instantly recognise these specific spike proteins (which would then be on the invading virus) if they enter the body in the future. Steps 1 and 2 can then kill the now known virus, almost before it makes you sick. If you do get symptoms, they’re likely to be mild.
Medical trials and distribution
The medical trials show that the vaccine produces 74-90% immunity against future SARS-CoV-2 virus invasion in an immunised person. Trials are continuing to establish this vaccine’s effectiveness against the new variants of the virus. At this point it seems there is at least some immunity to variants.
If you have had the Covid illness before, having the vaccine ensures even better memory in your immune system.
A person needs 2 doses of the vaccine, 4 to 12 weeks apart to ensure production of memory immunity. The injection is stored at normal fridge temperature of 20º-80ºC.
The injection is given in the upper arm. A patient may experience localised pain and redness and some may get some mild Covid-like symptoms as their immune system works to recognise and kill the invader (this is the same with any vaccine).
The vaccine is approved for adults (over the age of 18). At this stage, it cannot be used in pregnant or breastfeeding women or in children as the clinical trials have not yet been done in these groups. If you are allergic to a component of the vaccine, you also cannot have it. Fortunately, this is rare and easily managed medically.
It is safe to give to immunocompromised and immunosuppressed patients, on advice by their doctor, although they may have a weaker overall immune response.
Ongoing trials are being conducted on this and other vaccines around the world to get more detailed information on all aspects of the vaccines.
But let’s think about this.
Currently, the Covid mortality rate is about 2% (i.e. 2 or 3 people per 100 infected are dying) and many more are being permanently disabled by the Covid infection. On the other hand, of the 11 500 people in the Oxford/AstraZeneca vaccine trials, not one person has died and side-effects have been minor.
Which scenario is then more dangerous?
* Dr Lauren Wise is general practitioner with a passion for family medicine. She is part of the GGPC (Gauteng General Practitioners Consortium).
this article was originally published on IOL.co.za