COVID-19 explained: All you need to know about the immune system, reinfection and vaccine
With it being almost a year since the SARS-CoV-2 virus infected its first victim in Wuhan, it is now time to refurbish our knowledge about the virus. Since the start of the year, we have been exposed to a great deal of information about COVID-19, immunity and vaccines from many contradictory sources, often confusing us as to what is right or wrong. To avoid colossal damage due to misinformation, the World Health Organisation (WHO), along with social media giants and some countries' governments, started several initiatives to stop the "infodemic". Coined by WHO, infodemic stands for the overabundance of content that is both genuine as well as fake.
Now might be the right time to get your facts in place concerning the novel coronavirus, immunity and vaccines. In an interview with The Bridge Chronicle, Dr Himanshu Dewan, a Senior Consultant and Head of Critical care, currently working in the COVID-19 ward of the QRG Healthcity in Faridabad, Haryana, explains the functioning of the immune system, the efficacy of immunity-boosting products and COVID-19 reinfections.
Can you explain how our immune system works to fight viral diseases?
The human body has layers of immunity. First is the 'surface immunity.' When a virus comes in contact with the body surface, it sends antibodies to take care of that virus. Antibodies are proteins in the body meant to neutralise pathogens by presenting the pathogens to the eating cells which then eat away the virus.
If the virus load is more than what the antibodies can handle, the virus can invade the body or the host. Inside the body, there is a degree of 'non-specific immunity' which gets activated to help the body fight against any intruder.
After the host has been exposed to a virus for a while, he/she starts developing 'specific immunity' in the form of antibodies for the specific pathogen. After that, the body produces long-term antibodies like IGG antibodies to prevent reinfection or extreme symptoms in case the body gets exposed to the pathogen again.
Why are some people getting infected with COVID-19 if they had developed antibodies against the virus?
There are two important things to note here. One, the severity of symptoms when he/she was infected first and whether an antibody response was developed. Every COVID-19 patient doesn't develop an antibody response. Two, the virus can change its morphology in due course of time.
That means, the viral proteins, which are recognised by our body to produce antibodies, mutates in a period of three to six months. Through mutation, the virus changes its proteins so that they can evade the body's antibody response. Therefore, a mutated virus won't be recognised by a re-exposed body and hence the body will be prone to reinfection.
What factors determine how good our immune system is?
The strength of a person's immune system can be classified according to a 'baseline'. All those who meet that particular baseline are 'immunocompetent' and those who do not are 'immunocompromised' or 'Immuno-incompetent.'
How does an immunocompetent body's immunity vary in their response and what factors determine the differences?
The number one factor is genetics. Then comes the degree of exposure to infection a body gets. People from lower economic status or rural backgrounds tend to have very high baseline immunity because they are exposed to infections day in and day out. This makes their response to infections much better than the response of people who are less exposed to infections on a regular basis.
The next factor is nutrition. Consumption of Vitamin C, D, and Zinc among others is integral to maintaining a strong immune system.
What are your opinions about the immunity boosting products or ayurvedic products claiming that they provide protection from COVID-19?
A person who is having a balanced diet doesn't need to use any supplements to increase immunity. But people nowadays with their modern lifestyle and changing eating patterns can develop vitamin deficiencies. One should take vitamin supplements only after he/she is medically tested and shown to be deficient in a particular vitamin. Consuming vitamin supplements excessively won't increase your immunity any further.
Now, let's talk about products claiming to provide protection from COVID-19. Modern or allopathic medicines have to be tested using scientific experiments like randomised control trials to prove their efficiency. Drugs like hydroxychloroquine and lopinavir/ritonavir that were popular once lost their momentum because trials showed that these drugs didn't make much difference in the fight against SARS-CoV-2. This isn't the case with Ayurvedic products.
Ayurvedic and homoeopathic products contain micronutrients like Vitamin C and Zinc which will boost your immunity anyway. The issue is the exact constitution of these products isn't known. Therefore, the consumer should take them in moderation. Some of these products contain heavy metals and these can be damaging to your body. We have seen people who excessively consumed these ayurvedic/homoeopathic products, that may possibly contain heavy metals, develop damages to nerves and other body organs.
What is herd immunity and will it work against COVID-19?
As long as there are people who are not immune to the virus, the virus will have a body to replicate and transmit. But then, there would come a time when there aren't enough bodies left for the virus to reach. For this to happen, 40 per cent to 60 per cent of the population has to be infected. After we reach this number, the chances of interaction between an infected person and a non-infected person become very low, effectively lowering the transmission rate. But we have not been able to reach this number yet with COVID-19.
Another reason why herd immunity won't work is because COVID-19 is an RNA virus. There are two types of viruses- RNA virus and DNA virus. The DNA virus is more stable because they don't change their morphology rapidly. But the RNA virus mutates and changes its morphology much faster. Hence, it won't be possible to achieve herd immunity for such rapidly changing viruses.
What factors determine the longevity of protection from a disease after vaccination?
Stable viruses like mumps or rubella, for which we are given a vaccination for at a young age, haven't changed their morphology in decades. For these stable viruses, one or two vaccination can give a person lifelong immunity. Then there are viruses like the flu virus or influenza that change their morphology frequently.
For these, you have to take a vaccine every year. Not because the initial vaccine was ineffective but because every year you may be invaded by a newly packaged or refurbished virus.
With the changing nature of the SARS-CoV-2 virus, the virus that causes COVID-19, my presumption is we might need to take multiple vaccinations a year. But now they (pharmaceutical companies) are trying a different approach in developing a vaccine by targeting the spike protein of the virus.
The spike protein of a virus remains more constant even during mutations. Most of the vaccines carry antibody protection against these spike protein, which I presume will give quite a degree of immunity against the virus after one round of vaccination.